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Sverige class (1915)

Sverige class coastal battleships (1915)

Swedish Navy 1912-70
HSwMS Sverige, Drottning Victoria, Gustav V

Sweden’s last Pansarkepp

Sweden’s very last coastal battleships is a saga out of itself. Largest ships ever built in Sweden before even the Great War broke out, completed after many delays in 1917, 21 and 22, they became the flagships of the coastal defence until faster, more modern cruisers (The Tre Kronor class) were chosen for the task of leading the three resident naval forces of the country. Largely funded by popular support, these three vessel looked superficially like regular-pre-dreadnoughts, but were every bit tailored for the need of Svenska Marinen.
By size and tonnage they dwarved everything built before, notably 1906 Oskar II. They would have a very long career, as customary in the Swedish Navy, being rebuilt and modernized to face WW2 and a large part of the Cold War, although completely obsolete by that time and relegated since a long time to secondary duties.

Design Development

Rendition of the future Sverige in 1912 during the fundraising campaign, now at the Sjöhistoriska museet

Sweden witnessed the naval arms race after dissolving the union with Norway in 1905, tensions rose again with the Russian Empire, Germany, and Norway and by 1911, their ships were cruising around in the North Sea. In these circumstances, the Swedish Government only avalized the construction of Oscar II, a typical pre-dreadnought but with 8-inch guns for 17.8 knots and she was found totally inadequate, especially after the launch of HMD Dreadnought, likely to be followed by other nations.
The admiralty pushed fir a new class with extra seaworthiness, better armament, better protection and extra speed, and with the latest technologies, notably in fire control. In 1911, with the dreadnought race ongoing, the parliament voted at a small majority funds for the “F-boat” program the last of all proposals prepared and examined, A, B, C, D, D1, D2, E, E1, E2 and F, ranging from 4,800 to 7,500 metric tons and with various armaments and speed to match.

The Sverige-class coastal battleships were the largest ships ever to serve in the Swedish Navy at that point. Their design was totally new and inspired by other nations’ own dreadnought designs. Their armament was head and shoulders above the previous Oscar II (see below) with four 283 mm (11 in)/45 cal.
Bofors guns in twin turrets (rather than two 210 mm in single turrets) and eight 152 mm (6 in) Bofors guns a single superfiring twin turret and six single broadside made her battery. Just one on three of the Pansarkepp was ready on time to serve at the end of WW1 but all three formed the backbone of the Swedish Navy during WW2, next interwar constructions revolving around cruisers, destroyers, and submersibles.

Enhanced swerige-class coastal battleship project, before the post-war ban of new constructions: She would have been armed with six 305 mm in twin turrets and six single 105 mm guns.

The Sverige-class was a new take on the coastal Defence ship, with an heavier armament, better speed, and armor. But still, the hull was tailored not for high seas but for local archipelagos and shallow waters. Their tactical doctrine and operations were also new. Indeed they formed the core of an open-sea battle group (which should have originally comprised four and not three ships), and were meant to operate with cruisers, destroyers, torpedo boats, but also air reconnaissance. This small battle group was to operate as a defensive force only.


Painting at the Sjohistoriska museet
“Sverige” (“Sweden”) was initially decided in 1911 to start the type F, submitted by the Admiralty, approved by the parliament. She was properly funded and voted. However, there was a change of government the next year. The new liberal majority prime minister Karl Staaff decided against new military spendings and against this ship. Thus, the project was postponed until an exhaustive analysis took place, before motivating any further decision.
However soon, a national move (parlty helped by a critical press and fuelled by international nationalism) a campaign was quickly setup to raise more money. In total, over 15 million crowns were gathered, and this helped the ship to be voted in 1911 (under a price bill of 12 million). This law was called the “Pansarbåtinsamlingen”. Breween the press, popular optinion, the parliament and funding, the government was cornered to authorize construction. The ship was also called called “the people’s gift to the country”.

The two next were voted in 1914 by the same government, now with a war to motivate it. These were called HMS Drottning Victoria and Gustav V. Both were laid down in 1915 due to material shortages, launched in September 1917 and January 1918 respectively. The war ended before any could be operational, but fortunately the country never left its neutrality stance. Both last vessels were completed in 1921 and 1922, modified with the experience from Sverige and modified in the interwar during completion.

Design of the Sverige class

Brassey’s Naval annual armour scheme of the class, 1923

Hull and general design

The hull was 120 meters long (390 ft) for a 6,852 tons standard displacement which rose to 7,516 tons fully loaded for HSwMS Sverige, of another level also compared to Oscar II. Probably in 1914 they were the meanest coastal ship in any navy of the time, worthy of a “pocket dreadnought”. Other sources gives 6,961 tonnes tons standard, 7,758 tons deep load for Sverige initially.
With reconstruction and additions in WW2 they rose to 7,239 tonnes standard, 7,755 tonnes full load.
As for dimensions, her two sister ships were slightly different, at 121.6 m (399 ft) long, but the rest was the same at 18.6 m (61 ft) in beam and 6.2 m (20 ft) in draught but 6.3 m (21 ft) for Sverige.

Armour protection layout

Armor scheme included the following:
-200 mm (7.9 in) thick belt, central section tapered down to 100 mm (3.9 in) and 60 mm (2.4 in) both ends
-Upper belt 100 mm (3.9 in) behind fore barbette and aft barbettes.
-Main turret 200 mm (7.9 in) front, 100 mm (3.9 in) sides, 50 mm (2.0 in) roof.
-Main Barbettes 150 mm (5.9 in) above the ammo wells,
-Secondary turrets 125 mm (4.9 in), 100 mm (3.9 in) barbettes.
-Forward conning Tower 175 mm (6.9 in)
-Armor decks ranged from 45 to 30 mm (1.8 to 1.2 in).
All in all it was 50 mm more for all figures compared to Oscar II, sufficient to deal against Armoured cruisers of the time, but a bit light to face contemporary battleships.


Engine telegraph on Drotting Victoria
To propel these 7,000 tons monsters, the machinery comprised four shafts coupled to Curtis turbines rated for 20,000 SHP total and 12 Yarrow-type coal-fired boilers. This figure was for the Sverige only. The two others had Westinghouse geared turbines rated for 22,000 SHP and were upgraded in the interwar to oil-fired models. The Westinghouse geared turbines manufactured by Motala Company for Gustaf V and Drottning Victoria, and rated for 22,000 SHP.
As for the range, Sverige carried initially 776 tons of coal, and later was added 100 tonnes of oil and it was 761 tons for the two sister ships (same for oil).


The armament comprised four 283 mm (11 in) 45 cal. Bofors that were equivalent to the German main battleship caliber of the time. The rate of fire was good at 17 sec. between shots but the turrets were rather cramped because of the partition between guns inside both turrets. The eight 6-in/50 caliber QF guns in twin and single turrets were rather a modern arrangement, more than usual broadside barbettes.


The Bofors 28.3 cm/45 (11.1″) Model 1912 were designed from 1912 for the Sverige class, and in service by 1917. Further projects of Pansarkepp were never followed-up in the interwar so they were the last. These guns were of built-up construction, with a hand-operated screw breech-block of the typical ogival type. They had a rather high rate of fire for the time (3-4 rounds per minute) and were considered to be quite accurate, making the ships quite a deterrent indeed for any capital ship.
In the 1930s a new and more aerodynamic “Arrow Nose Shell” was developed for increased range and compensate for the apparition of new, larger guns, notably in Germany the Schanrhorst’s 28 cm SK C/34 naval guns which had a 40,930 m (44,760 yd) at 40° elevation.
One of these guns (from Drottning Victoria) was preserved, now at the Karlskrona Naval Base.
They weighted 43.4 tons (44.1 mt) for a barrel lenght of 501.4 in (12.735 m), bore alone 484.1 in (12.295 m) and rifling of 414.0 in (10.515 m), 80 grooves.
They fired a Bagged type projectiles, 672.4 lbs. (305 kg) AP shells with a 220.5 lbs. (100 kg) charge.

Muzzle Velocity was 2,854 fps (870 mps), enabling a range of 21,435 yards (19,600 m)/18° later ported with the 672.4 lbs. (305 kg) Arrow Nose shell to 31,700 yards (29,000 m) at 25°, after gun cradle modifications. The penetration at 6,560 yards (6,000 m) was 350 mm of hardened KC steel at 0° (13.77 in) and at 19,690 yards (18,000 m) 155 mm (6 in) down to 87 mm (3.4 in) on a horizontal armor. The 350 tonnes turret elevated initially to 18°, later to 25, at 5° per second and traversed at 4°. Gun axes were about 83 in (210 cm) apart to avoid interference.


These eight 152 mm (6 in)/50 cal. guns were placed in a single twin turret forward, superfiring above the main 11-in forward turret, and six single mounts in single turrets, not unlike the British 1906 Lord Nelson class pre-dreadnoughts.
These 15.2 cm/50 (6″) Model 1912 were unique to the Sverige class. They were rather similar to the earlier Model 1903, used a hand-operated screw breech-block (ogival type).
In short, these 7.63 tons guns had a bore lenght of circa 300 in (7.620 m) and fired like the main guns at 3-4 rounds per minute.
They used a bagged AP 101 lbs. (46 kg) shell at 2,789 fps (850 mps) up to 15,000 yards (13,716 m) at 30° elevation.
Some ended after WW2 as land artillery, notably at the top secret “Kalix line” (northern Sweden), near Vuollerim in service until the 1990s amazingly. The fort was turned into a museum.


In addition, four 75 mm (3 in) Bofors AA cannons were mounted forward of the rear turret. No infos on these, even on the excellent navweaps.com.
There were also two anti-ship QF 57 mm (2.2 in) short-barreled Bofors and nine 6.5 mm (0.26 in) Machine-Guns
As customary for the time, the armament was rounded to two 457 mm (18 in) torpedo tubes.

⚙ specifications

Displacement 6850 tonnes, 7700 tonnes FL
Dimensions 120/122 x 18.6 x 6.25 m (390/399 x 61 x 20 feets)
Propulsion 4 shafts, Kockums-Curtis Turbines, 12 Yarrow boilers, 20,000 shp
Speed 22.5 knots as designed
Range 2,720 nm at 14 knots
Armament 4 x283, 8 (1×2, 6×1)x 152, 2x 75, 2x 57, 2x 6.5mm MG, 2x 450mm TTs
Protection Belt 200, Barbettes 150, turrets 200, sec turrets 125, decks 45-30 mm, CT 175mm
Crew 427

Reconstructions and modernizations

Sverige in 1929, before her major reconstruction
During WW2 this doctrine was still active and indeed they offered a smaller target to submarines, torpedo crafts or dive-bombers and minefields, some authors suggested they were taken in consideration in the decision by the Germans high command in WW2 not to invade Sweden in 1940. In fact, Jane’s 1938 edition classed these ships as battleships due to their use in a coherent battle group.


The 12 Yarrow boilers were later upgraded to oil-fired boilers in the 1930s on Sverige, but not on Gustaf V and Drottning Victoria for strategic reasons. It was decided to keep the ability to burn coal if Swedish oil supply was cut off. Also after reconstruction they started to diverged widely in appearance:
Gustav V had funnels trunked into a single one, upper works well modified.
Sverige had her fore funnel trunked back away from the superstructure (also modified) but kept the second funnel.

Armament Upgrades

-The underwater torpedo tubes were removed and the room was converted into an artillery central, feeding data from modern range meters, coupled with new fire control systems for the heavy, secondary and AA-gunnery
-Small guns and two 6 in guns were removed. Modern Bofors 75mm, 40mm and 20mm AA guns were installed instead.
-Gustav V had her forward superfiring twin 152 mm (6 in) turret removed but a gyro-stabilized AA artillery (4×40 mm bofors) mount placed instead.
-Sverige and Drottning Victoria had their midship single 152 mm (6 in) guns removed, replaced by the same.
-Main 11 in guns range augmented, between the 25° elevation and new shells (as seen above).
-New complement reached 450, making these ships appear even more cramped. They were not popular in WW2, but still the country’s “insurance card” against a menacing Kriegsmarine.

Modernization History

Sverige in 1931, in sea trials, post reconstruction
In 1924-1926 Sverige was given a new tripod mast, new director and fire-control centre and later on Drottning Victoria, same tripod mast and director, fire-control centre and both received paravanes. Gustav V was moderned later, between 1927 and 1930. Same midifications, but with her main mast cut and moved forward, delettion of six original 75mm/49 Bofors guns and addition of two twin 75mm/56 K/60 M28 guns.
In 1931-1937 all three saw radical armametn upgrades. Sverige received machinery and funnel modifications, mast too, new Curtis geared turbines and same armament upgrade as Gustav V.
It was the same for Drottning Victoria but she had 6 Yarrow mixed-burning boilers replaced by two oil-burning Penhöet, with fuel stowage modified to 360ts of coal and 273ts of oil. In additon to the twin 75mm/56 K/60 M28 she also received three single 25mm/55 K/58 M32 AA guns.
Gustaf V completed her prewar modernization last, with 6 Yarrow mixed-burning boilers replaced by two same oil-burning Penhöet (same figures) and same armament upgrade with in addition four single 25mm/55 K/58 M32 AA guns.

Gustav V in WW2

From 1938 and until 1942 they had limited upgrades. Sverige had four oil-burning Penhöet boilers installed, lost two 152mm/49 guns for two twin 40mm/56 K/60 M32, tw twin 25mm/55 K/58 M32 AA guns, and Drottning Victoria followed suite, but with two single 25mm/55 K/58 M32 and then twi more a year later.
In 1942 all three were upgraded again. Sverige had the two twin old 25mm/55 retired and instead a single twin 40mm/56 K/60 M32 installed as well as two twin 20mm/63 K/66 M40 (Licenced Oerlikon).
Drottning Victoria had all her seven 25mm/55 retired for the same, but instead of twio twin, seven 20mm/63 K/66 M40 (they replaced the 25 mm as a one-per-one basis).
Gustaf V had initially two twin and four single (8 total) 25mm/55 and they were all retired for four single 25mm/55, the twin 40mm Bofors and two twin plus four single 20mm/63 K/66 M40 AA guns.
In 1943 Drottning Victoria was the first equipped with a Swedish-built radar and after the war Gustaf V was equipped with a British radar. Sverige never received this upgrade.

Operational service
SMG 31738. Pansarbåten “Sverige” 3 maj 1915

The launch of Sverige, on 3 May 1915, by then the largest, heaviest ship ever in Sweden. King Gustaf V and his family but also Prince Wilhelm, Prince Eugen and Prime Minister Hjalmar Hammarskjöld were in attendance. After a short speech, the king pressed a button which released the ship from the stack bed. The launch ended with a concert at Gothenburg’s concert hall, followed by a banquet at the stock exchange. During firring out, the 28 cm guns were too heavy for the existing crane and thus, two special cranes were built for the task in Gothenburg.
Total cost armounted to 13,450,000 crows, (SEK 350 million by 2009 value).

HSwMS Sverige the only ship of her class ready to take part in WW1. After completion in 10.5.1917 in Götaverken, Gothenborg. Sweden remaining neutral in two wars and between, their career was not outstanding, but interesting and quite long nonetheless.


Sverige as completed

On May 10, 1917, the ship received her first crew and when fully equipped, departed with from Gothenburg to Karlskrona Royal Arsenal under command of captain Fredrik Riben, where she was to be docked for preparations and final acceptance sea trials. In Karlskrona it was found that her displacement was 90 tons less than calculated, which was something good for the standards of the time (it was often above). After ammunition and equipment were loaded, the new battleships left for Stockholm and dropped anchor on June 13, there and the following day, officialy commissioned with a grand ceremony.
The next months and in January 1918, she trained in home waters, including gunnery drills at the range, fleet manoeuvers and a short refit.

The Åland Expedition 1918:
As the war raged in Finland, by February 1918, it was requested fro Sverige to moved to the Åland islands, for protection against unrest. On February 13, a first expedition was sent there with the old HMS Thor. As the situation worsened, on the 17th both Sverige and Oscar II were sent to Åland. They sailed on the 18th after mustering crews and supplies, and arrived on the 20th at Arholma, waited into the ice, and were ordered afterwards to head directly towards Eckerö, Åland. Sverige monitored there the situation and helped evacuating civilians, together with the gunboat Svensksund.

The interwar:

Sverige in 1929 and 1931

The spring and summer of 1918, saw the battleship back with the fleet as flagship, performing exercises on the west coast. As the Spanish flu ravaged the country, many ships were de facto out of commission, with quarantined, ill or absent crews. Every day steamboats picked sick sailors ashore and there were normal military funerals. On October 4, 1918, Sverige was in drydock refit at Karlskrona.
She took part in the celebrations of Crown Prince Gustaf Adolf’s marriage to Louise Mountbatten, with her sister HMS Drottning Victoria, escorted by the destroyers Wrangel and Wachtmeister in 1923 in England, joined by the cruiser Fylgia recalled from an overseas expedition, in Sheerness, by 2 July. Queen Victoria later visited Sweden, and assisted to rowing competitions against English ship crews.
In 1924–1925, Sverige was modernized a first time, quite extensively. By that time, her new captain was in 1926–1927 Gunnar Bjurner. The next one was performed in 1931–1933, and by 1936, she had her anti-aircraft artillery strengthened and further modernizations, plus new steam boilers. In 1938, all coal-fired boilers were removed and replaced by new oil-fired ones and this choice was dictated by the poor accuracy results when Drottning Victoria had to cancel an anti-aircraft exercise due to smoke interference, totally obscuring targets.

On March 15, 1939, Sverige returned to Karlskrona shipyard for another efit, with oil tanks installed and extra accomodations for the crew, new ammunition bins for the main and secondary artillery, new pole and boom, 110 cm gyro-stabilized headlights and 40 mm m/36 AA guns mounted.

Second World War
By September the other planned modifications were cancelled. On April 9, 1940, the ship was back in service with the coastal fleet.
She will soon have neutrality bands painted on her hull, like all other Swedish ships at the time. With the occupation of Denmark and Norway and weakening out of Finland, Sweden’s strategic position seemed jeopardized. The defense entire east coast needed to be defended, both against the Soviet Navy and the Kriegsmarine it seemed after the short-lived Germano-Russian pact.
On July 17, 1940, an explosion occurred in one of Gustav V’s boilers, ans since she was the flagship, it was transferred to Sverige, remaining so until the end of the war.
The winter of 1940/1941 was very severe and she was stuck in pack and it was decided to have the crews of all stuck Swedish ships trained to fight as infantry on ice in case of an invasion. Sverige also had her hull entirely sprayed with a lime-based white paint as a winter camouflage, possibly with black and white camouflage nets applied on her superstructure. Her appearance will change again in 1944.

On January 18, 1941, the submarine HMS Svärdfisken accidentally collided with Sverige while underwater and if the former suffered severe damage, towed by the battleships to Stockholm shipyard, the latter only sustained damage to her port inner propeller, shaft and struts. She was also drydocked for repairs. The remainder of 1942, 43 and 1944 so little action. She was moved from place to place depending on the evolving situation, notably receiving her final complex green-base camouflage, with several tones, something interneded for her to blend-in close to any archipelago island. When stationary camouflage netting was added to mask her superstructures.

Sverige in WW2, with neutrality bands, prior to be camouflaged in 1942.

Sverige prow at full speed in 1944, showing her side crown.

On May 7, 1945, the war seemed over in Europe, the fleet’s constant battle readiness was maintained until the 16th, and it was decided to end the night blackouts. The fleet resumed her prepwar exercizes and activities. A refresher was needed, and Sverige took part on June 6, to a shooting competition. This was followed by the entire coastal fleet entering Stockholm. King Gustaf V came aboard Sverige distributed competition’s prizes, and to thank the officers and crews present for their vigilant guard during the war.

End of Career
By August 11, 1947, the now obsolete battleship was scheduled for decommission. Her flag insignia was lowered from her top mast for the last time. After decommission, Sverige was mothballed for a time, until stricken on 30 January 1953. Placed on the disposal list, she was sold in 1958 to a Swedish company and scrapped at Karlskrona. Since 1986, one of cannons is now exhibited at Rävåskullen, Karlskoga, placed there for the city’s 400th anniversary.

Drottning Victoria

In early service, 1920s
“Queen Victoria” was launched at Götaverken on September 15, 1917. Her postwar-interwar service life resembled that of Sverige, with two major reconstructions and modernization, fleet training and ceremonial duties with Sverige.
Fast forward and Drottning Victoria during the winter of 1939–1940 was stuck by severe icing in the Horsfjärden area. Her crew was trained and reconverted as infantry in case of an invasion. In connection with reports of the Kriegsmarine movements ahead of Operation Weserübung, the Commander of the Coastal Fleet wanted Drottning Victoria and a fighter group to moved to open water as a deterrence.
As an amusing anecdote, on board the Drottning Victoria for a period there was the ship’s pet dog Nicke, a shaggy fox terrier who was taken care of by the crew. Nicke is mentioned in several places in the ship’s logs and had a specially made sailor’s suit and its own service book made. It appeared it was mustered on board on 1 January 1940 as a 3rd class seaman (ship number 900) and that he was later appointed corporal and then furrier according from October 31, 1943. Nicke remained on the ship at least until August 1946.

Ceremonial transfer of the body of Queen Victoria of Sweden from Swinemunde to Stockholm aboard “Drottning Victoria” (Bundesarchiv).

Drottning Victoria after 1931

Drottning Victoria was deactivated in 1948-49, stricken, and sold for scrap on March 22, 1957, then Scrapped in 1959 in Karlskrona.

Drottning Victoria prior to deactivation in 1959

HSwMS Gustav V

Gustav V after 1930

HSwMS Gustaf V was built at Kockums Yards, in Malmö. The yard used Sverige’s original drawings and construction work went fast, without a hitch. Shortages of materials due to other priorities during the great war meant it lagged behind especially due to bottlenecks for equipments acquired outside the country. Armor plates notably were ordered from the United States, and arrived basically months out of schedule.
On 31 January 1918, she was launched and baptised by the wife of Crown Prince Gustaf VI Adolf. Due to the large, unprecedented size of the ship there was a legitimate fear it would slip at launch and hit the opposite side of the harbor basin, a short distance manageable by previous vessels, but not this one. To prevent this, heavy chains were attached to arrest her momentum. Also on the opposite side a “buffer” of wooden logs was installed to damp a possible collision. But the launch proved successful, the chains braking her mid-way as planned.

She was fitted out and still delays arose from material shortages compounded by a strong labor shortage in 1917–1920. It was so severe the yard requested to terminate the contract in the mood of disarmament and peace some even asking the removal of their armor and rebuilt Gustaf V and Drottning Victoria as passenger ships. By the winter of 1921/1922 however work resumed eventaually and both ships were completed as intended. Gustaf V started sea trials and showed her new machinery reduction gear worked well. It total her cost has been of 14,220,000 Swedish Krona (44,022,000 USD today). Some criticized her construction concept as being already obsolete and a waste of money. But 1,293,295 crowns were obtained by the Yard to cover increased costs from procurement delays.

Aft view of Gustav V showing her Royal stern Crest, early WW2 as she has neutrality bands but is not camouflaged yet.

The early interwar new relations of Sweden with emergin states like Finland and the Baltic States, was accompanied by the Swedish Government’s goodwill and this led to several official exercises conducted in these countries. On 5 July 1924, Gustaf V and HSwMS Drottning Victoria, four minelayers went for example to Tallinn, and later the entire Swedish Coastal Fleet (36 ships) went to Helsinki. The summer of 1926 saw Gustaf V and Sverige visiting Copenhagen after exercizes in the southern Baltic.
In 1927–1930 Gustaf V her her first modernization.
After the death of Queen Victoria in the spring of 1930, Gustaf V and Drottning Victoria escorted by the destroyers HSwMS Ehrensköld and Nordenskjöld sailed to Swinemünde (9 April) to have the Queen’s remains carried onto HSwMS Drottning Victoria and they returned to Stockholm, the remains being landed and paraded on the royal barge Vasaorden.
On 4 April 1933, Gustaf V ran aground off Malmö but she was towed away on 6 April 1933 and repaired until the end of the year.

She her had second major modernization in 1936–1938 and on 9 March 1939, took part in a large air defense exercise out in Karlskrona. One aircraft attempting to land in the dark collided with Gustaf V’s combat mast. The crew was killed and the aicraft destroyed, but damage for the ship was negligible.

By 1939 Gustaf V being the most recent Swedish capital ship, she became flagship of the entire Coastal Fleet. On the night of 17 July 1940 during an exercise however, west of Gotland, she suffered a boiler explosion, which killed eight (the whole boiler room crew) and two on deck near one of the air intakes were badly burned. They were quickl evacuated by a minelayer to Visby Hospital, but one later died. While in Hårsfjärden it was decided by the commanding admiral to make HSwMS Sverige the new flagship, which she remained until the end of the war. Gustav V was repaired in Stockholm for a month and return to service. Nothing much happened during that time. Like Sverige and Drottning Victoria she had received neutrality white bands at the start of the war, and she was camouflaged by 1944.

Gustav V in 1945, showing her newly installed radar.

After the war, Gustaf V took part in a ceremony held in Stockholm, being thanked by King Gustaf V for their “vigilant guard” during the war years. Indeed the crews had been mobilierf on high alert for the duration of WW2, with few rest or leaves, abbreviated refits, and a very high availability time. She returned to Karlskrona to received a new radar facility. HSwMS Sverige was discarded in in 1947 and Gustaf V took her place again as flagship.
It seems she served mostly as training ship for the remainder of the early cold war years, with the specter of a confrontation with the Soviet Batltic Fleet.
Gustaf V was the last Pansrkepp in service in the Swedish Navy -as for any navy- and she was stricken on 1 April 1957. She was mothballed at the Berga Naval Base, south of Stockholm until 1967 however, unlike the others. There, she was used as a mooring point for destroyers. Two her her secondary 6-in guns were removed to be installed into the secret Kalix Line in Norrbotten, placed in Häggmansberget casemate.
In 1970 at last, the very last coastal battleship in the world was sold for BU in Gothenburg. This is rather sad that she was not preserved as a floating museum, but this was still rare in the late 1960s (and costly).

Gustav V towed for scrapping in Gothenburg. She still sported her wartime camouflage, something that became a feature of the Swedish Fleet in the cold war as well.

The same in scrapping

Read More

Rare original color photo, camouflaged in 1944 of Drottning Victoria (small size, cc).


Naval Weapons of World War Two” by John Campbell
Från monitorer till pansarskepp” by Per Insulander and Curt S. Ohlsson
Harris, Daniel G. (1992). “The Svierge Class Coastal Defense Ships”. In Gardiner, Robert (ed.). Warship 1992. NIP
Hore, Peter; Ireland, Bernard (2013). The Illustrated Encyclopedia of Battleships & Cruisers. Anness.
Sundberg, Ulf (2018). “The heavily Armoured ShipSverige (1915)”. In Taylor, Bruce (ed.). The World of the Battleship. Seaforth Publishing.
Utredning och Forslag angaende Sjorkrigsmaterielens sammansättning m.m. avgivet jamlikt Kungl. Swedish National Archives


navweaps.com 11-in/45 1912
navweaps.com 6-in/50 m1912
navypedia.org/ sverige class
commons.wikimedia.org Sverige_class cc photos



Model Kits

3D printed modellbauray Sverige class 1:700
On scalemates: Fairy Kikaku 1:700, in addition to modellbauRay. That’s it.

HMS Pretoria Castle (1938)

HMS Pretoria Castle (1943-46)

United Kingdom – Training Aircraft Carrier

HMS Pretoria Castle (F61) was a freshly completed Harland & Wolff, Belfast-built Union-Castle ocean liner (the makers of the Titanic) requisitioned and converted into a Royal Navy armed merchant cruiser (MAC), and then in July 1942 as an escort carrier (Commissioned as escort carrier on 29 July 1943). Capable of carrying only 21 planes despite her size, she was not a happy conversion, and served as a trials and training carrier, being converted back into a passenger liner as Warwick Castle in 1946, until 1962.

The Liner turned Aircraft Carrier

The idea of using passenger liners as a base for conversion into aircraft carriers went a long way, going back to WWI. The first in the Royal Navy was HMS Argus, still in service in WW2. However the norm, especially for convoy escort, was to choose existing merchant vessels for conversion.

Pretoria Castle in 1939, before requisition

Harland and Wolff built initially Pretoria Castle as a regular “packet boat” (the old denomination), in Belfast, and she was launched in Harland & Wolff in 1938 and completed by April 1939 (see her career for more). The Admiralty requisitioned herto be pressed as an auxiliary cruiser in the Royal Navy by October 1939. To escort other ships, only the most recent and faster vessels are converted into armed merchant cruisers, and this was her fate. She received eight surplus WWI 6-inch guns (152 mm) and two 3-inch (76 mm) guns and entered service as an AMC in November 1939. In this role she served mainly in the South Atlantic.

By July 1942 the Admiralty now needed aricraft carriers and the AMC Pretoria Castle was purchased outright for conversion (she was leased until then) to an escort carrier. This was to be done at Swan Hunter on Tyne. For her new role she had gher superstructures removed to the weather deck, she received a hangar above and flight deck. She was commissioned by July 1943 but operated as a trials and training carrier and not with the fleet due to her incompatible speed. She saw as a result no active combat service.

Design of the class

Built from a civilian ship, the aircraft carrier was following the same conversion methodes already used on HMS Audacity and followed by others. It’s only the lack of available yards that prevented the Royal Navy to proceeded to more conversion. Thus, Pretoria Castle was converted from July 1942 to August 1943, more than a year, which was above average. Workforce was used for more pressing needs and she suffered from slowdowns. However when completed, HMS Pretoria Castle became the largest escort aircraft carrier in the world. She was also the third, after Audacity and Activity. More would follow, but smaller, such as the 14,000 tonnes Vindex class and related Campania. However this was over since via lend-lease the US procured soon a flurry of new ships, HMS Archer, and the Avenger, Attacker and Ameer classes all came from US Yards.

Conversion work in 1942 or rather refit in 1944-45 given her camouflage. Date unknown. Note the hand-painted pennant.

Hull and general design

As completed, HMS Pretoria Castle was not to be used operationally. From the start, she had diesel engines, something which could be handy for long escort missions, and better, a longer, wider flight deck that was available on average escort carriers. But these advantages precisely turned her as a preferrable carrier for trials, not training; Indeed for the latter, HMS Argus, when not taxiing aicraft or sent in operational theaters, was designed as the default training carrier. So since the start, Pretoria Castle was not meant to train pilots later asssigned to escort carriers, but rather to test models that will be later assigned to the fleet carriers.

Her facilities were not pushed far: Her hangar was a single space, only meant to house 21 planes total (a permanent deck park would have bring this to 36-40 if operational). Part of it was used as a workshop to tune up the planes to be trialled, prepare them or repair them after accident, which were highly likely. She had roomy facilities for mechanics and the test pilots and nice living conditions as an inheritance of ther original liner’s construction.

The final design shows a flight deck that was shorter than her oveall lenght, narrowed both aft and forward, the latter bieing supported by a serie of pillars. The hangar started past this semi-open space above the bow weather deck. It went back short of the stern, rounded, which was left free to mount a large AA gun, later to be decided.
The hangar has been made tall enough to accept any present and future models in use in the RN, including American ones. But facilities only consisted in a single catapult and a large axial lift, large enough to move up and down any non-folding wing model.
Her original portholes were all welded shut and plated over, less a serie just below the hangar. The latter was also dotted with the usual cutouts for service boats and life rafts, and the hangar walls was also alternated by sponsoned AA gun positions.

Pretoria Castle’s island was rather small and diminutive. It was placed on the usual starboard side, on a short overhanging platform supported by struts, clearing out the entire flight deck width. The island was limited to just a single stage enclosed map/utility room and topped by an open air bridge, with the usual ship’s commands and binoculars. There was a standard rangefinder for the main 4-in guns aft of the island, which ended with a thick mast supporting a lattice platform made for the installation of radars and antennae (see sensors).
To operate amphibians and seaplanes, the ship also had a starboard side crane, aft of the island.

Armour protection layout

Unlike regular fleet carriers and like all escort carriers, Pretoria Castle came unprotected. This came as another reason not to press her on the frontline. During her conversion she saw the addition of a light armour protection over the magazines (box type) and steering gear. It was shrapnel-proof and probabl around 1-inch or less (35-40 mm). However her underwater compartimentation could be turned into an ASW protection by creating or enclosing empty compartments, with doors plated over or welded shut, alongside her waterline. Neither the flight deck or hangar were protected in any way. In fact to compensate for the flight deck additon and hangar, more ballast is added.


Pretoria Castle being a merchantman, a liner not for the prestigious blue ribbond transatlantic line, but the more shoddy but important line to South Africa, her mahinery is made for efficience, range and reliability, not speed. Thus she is given two civilian grade Burmeister & Wain Diesels rated for 16,000 bhp (12,000 kW) total, 3,284 NHP. She has also 2,430 tons of diesel in her tanks, enough for a comfortable 16,000 nm trip at 16 knots, quite sufficient for the UK-Le Cape long west african road.
In reality she was used as AMC on the same road, but from Freetown and down to south pacific waters and Indian ocean.



Pretoria Castle was armed with the bare minimum, two twin compact 4-inches 45 caliber (102 mm) QF Mark XVI mounts, shielded. They were installed on the only place large enough to accomodate them, on the poop. Thus, their arc of fire was limited to the rear of the ship.
Quickspecs: Fixed QF 35 pounds (15.88 kg) HE or 38.25 pounds (17.35 kg) S.A.P. 9 Ib filling, Vertical sliding-block Breech, hydro-pneumatic recoil 831 mm (33 in) elevation -10 +80°, ROF 15–20 rpm, mz 2,660 fps, Range 19,850 yard/45° alt 39,000 ft/80°, mount 4,495 lb (2,039 kg), crew 8.


Eventually the two planned octuple pompoms were never installed. Pretoria Castle emerged with no less than fourteen sponsons mounts, large enough for the twin version of the 20 mm Oerlikon gun:
These seven sponsons either side were not placed the same way, the four outer ones were on larger sponsons. It’s possible the remainder five, which protruded far less, were meant originally for single mounts.
Upgrades: None. By January 1946 she had kept the same two twin 4-in/45 Mk XIX gun and her fourteen twin 20mm/70 Mk V Oerlikon as well as her original type 279 and type 281 radars


Pretoria Castle was given a sturdy mast with a platform to fit radars, and when completed, she received a type 279 and a type 281 radar. She also saw the installation of suitable communications for control and direction of aircraft, and ship navigation.
Type 279 Radar: 1940 Early-warning radar Frq 43 MHz PRF 50s, Pwt 7–30 μs Range 50 nm PW 70 kW
Type 281 Radar: 1940 Early-warning radar Frq 86–94 MHz PRF 50s Bwt 35° Pwt 2–3/15 μs Range 115 nmi alt 30,000 ft PW 1-350 kW

Air Facilities

Total surface for the flight deck respresented 3,977m² (42,800 Sq ft), and it measured 170.7 meters (560 ft= by 23.3 meters in width (76 ft). The single hangar below was 70.4 meters long (231 ft) by 18.5 meters in width (61 ft) and 5.3 meters in height (17 ft), for an overall surface of 2,100m² (22,600 Sq ft) and a volume of 11,130m³ (393,000 cu ft). The flight deck was rectangular, with a narrowing section aft, and a longer one forward.
HMS Pretoria Castle was provided a single lift forward measuring 13.7 meters in lenght (45 ft), 11.9 m width (40 ft) for 6.8t.
She was also provided with a single C-II Catapult installed forward and able to pull out a 6.4t plane at 122km/h. Thus was newly design prototype cordite fired catapult, and she was the first ship to test it. There were six arrestor cables aft, and two crash barriers before the launch area where the axial catapult was located.
To resupply the air park she was given an Aircraft fuel stowage of 345,500 liters/Imperial Gallons.

Air Group

Capt. Eric (“Winkle”) Brown’s Seafire Mark 45 TM379, on trials carrier HMS Pretoria Castle, July 1945. The Seafire Mark 45 was the last wartime evolution of the famous type. It had the new Rotol contra prop, modified fin, rudder and tail hook. Artwork depicting the scene

Mini Bio: Captain Eric Melrose “Winkle” Brown:
CBE, DSC, AFC, Hon FRAeS, born 21 January 1919 died 21 February 2016. British Royal Navy officer, test pilot of legend. He flew 487 types of aircraft, more than anyone else in history, holds the world record for the most aircraft carrier deck take-offs and landings (2,407+2,271) and achieved many “firsts” in naval aviation history like of a twin-engined aircraft, tricycle undercarriage, jet aircraft, and rotary-wing aircraft. He flew almost every category of Royal Navy and Royal Air Force aircraft type from gliders to fighters, bombers, amphibians, flying boats and helicopters in his long career. During WW2 he also tested German, Italian, and Japanese aircraft, including the latest and most dangerous jet and rocket aircraft. He also was a pioneer of jet technology, like the dangerous high-speed DH 108 “swallow” delta wing jet to attempt the sound barrier crossing.

Support Naval Encyclopedia

Fairey Albacore Mk.VC from 817 Squadron in 1944-45. Can’t find any photo of the “permanent park” Sea Hurricanes or Swordfish aboard.
HMS Pretoria Castle had a capacity of 21 planes, and the “standard” air group in 1944 was assumed to be 6 Sea Hurricane and 12 Swordfish according to navypedia.
She saw a wide variety of models on her decks given her role, doubling as training carrier: Fulmar, Sea Hurricane, Seafire, Martlet, Corsair, Albacore and Barracuda among others in WW2 saw action on her deck. As for photo evidence, she shows for sure the Seafire as well as the Fairey Firefly in action.

Fairey Fulmar taking off from Pretoria Castle, probably soon after completion.

Airacobra first landing on Pretoria Castle, 4 april 1945. Eric Brown was testing the tricycle configuration for the first time on a carrier.

Fairey Firefly from Pretoria Castle in flight

Fairey Firefly, wings folded before being struck under.

⚙ specifications

Displacement 17,392 GRT or 19,650 standard, 23,450 tons FL
Dimensions 594 x 76 x 29 ft (181.1 x 23.2 x 8.8 m)
Propulsion 2 shafts Burmeister & Wain Diesels, 16,000 bhp (12,000 kW); 3,284 NHP
Speed 18 knots (33 km/h; 21 mph)
Range Diesel oil 2,430 tons for 16,000 nm at 16 knots
Armament 2×2 102mm/45 QF Mk XVI, 14×2 20mm/70 Oerlikon Mk II/IV
Protection Splinter protection only over the magazines and steering gear
Sensors Type 279, Type 281 radars
Air Group 21, see notes
Crew 660+

HMS Pretoria Castle in Service

Early Service as an AMC

By 11 October 1939, she was armed and “militarized”, painted not in grey, but with a black hull and buff upper works and funnel. The requisitioned liner was Commissioned for service as HMS PRETORIA CASTLE. She was assigned to escort convoys in the South Atlantic, based at Freetown, Sierra Leone, West Africa.

In December, she Carried out sea trials after conversion completion and the 21 she sailed from Belfast, embarking ammunition and sailed to Freetown.
By January 1940 she arrived at Freetown and was prepared for Atlantic convoy defence. In February she is deployment for more escort missions, which also turned out to go to and from West Africa and Indian Ocean. Thuis routine went on until September. By that time, she is warned of German commerce raiders active in the South Atlantic.

In October, she join military convoy WS4 to supplement escort during their passage to Freetown. On the 11th she Joins WS4 divided into a fast and slow sections, and stayed with the latter up to Freetown, escorting six merchant ships. on the 15th she is detached and redeployed with the heavy cruiser CORNWALL as Ocean Escort for WS4 to CapeTown.
On the 26th she is detached to escort SS SCYTHIA and WARWICK CASTLE into Cape Town and three days later rejoins WS4.
On 2 November she escorts four merchantmen as part of WS4 SLOW to Durban and arrived the following day. By December she is back to Freetown with a routine convoy from Cape Town.
By January 1941 she joined the ‘Atlantic Trade defence’ and by April-May she is deployed with HMS REPULSE and the light cruiser MAURITIUS escorting the military Convoy WS8A into Freetown.
By June to December she escorts other routine convoys on the usual Freetown-Cape road.
This went on in 1942 until she is Nominated for conversion as CVE and joined UK in April and in May she is prepared for Paying-off and conversion.
The RN considered purchase from Union Castle, and in July conversion startes. She is indeed purchased on the 16th. In December she sees the removal of all upperstructure and later fitting of the flight deck and catapult.

WW2 Service as F61

In July 1942, Pretoria Castle starts her harbour trials and on the 29th, she is commissioned for service as a “Trials Carrier” stationed in the Western Approaches Command area. Next month, in August she performed her official sea Trials in the North Sea, followed by post-trials fixes and finishin working out. On August 10, she sails for her shakedown cruise and passage to Rosyth, arrving two days later, and in the Clyde, she complets her trials and start her first aircraft deck landings. She then takes her semi-permament position, anchored off Rothesay between trials.
Trials went on until the end of September, and October, until she has her first operational duty with 825 Squadron aboard, pilots making qualifications.

As a note here, 825 squadron was created in 1934 and deployed on Eagle and Glorious. After the latter is sunk in Norway, it is redeploed in UK and covered the Dunkirk evacuation. It took part of the Bismarck hunt, Atlantic operations, the channel dash (first from Furious then Ark Royal), the arctic convoys from HMS Avenger and later Vindex in 1943. By the summer of 1942, it likely operated the Fairey Swordfish II and Hawker Sea Hurricane IIc. The unit also was made famous later by the Falklands War in 1982. It still exists as a primary helicopter unit.

Only Escort mission
As the need for escort is strong, HMS Pretoria Castle is deployed with this operational squadron to escort military Convoy DS46 during passage to Reykjavik, arriving on the 29th. The following day she escorts Convoy SD46 back to the Clyde estuary.

In November she is Detached on arrival to resume trials duties. On the 29th she collides with the Escort Aircraft Carrier HMS RAVAGER, also deployed in the Clyde area for Deck Landing Trials. Damage is lights, they are repaired and she resumed trials until the end of the year.
By January 1944 she is deployed in the Clyde and nominated used for T6 HARVARD (lend-lease Texan, training monoplane) trials, to establish effective deck landing by the latter aircraft, using existing arrestor wires, something that needed confirmation. From there, this enable the option for the FAA to advanced trained thir pilots with this model.
In February 1944 Deck Landing trials are performes with new version of the SEAFIRE, Wildcat (Formerly Martlet) HELLCAT and AVENGER (Formerly Tarpon), and in March concentrates on new Seafire versions, which is the most capricious and fragile of the lot by far.
In April she startedr CORSAIR Mk.I landing trials.
On the 25th she is sent for a routine overhaul and maintenance, through May in drydock followed by post-refit Trials in the Clyde and resuming her activity. In June she tests Radar Interception trials with the SEAFIRE, in North Western Approaches, out at sea.
By July she resumed standard deck trials but on the 14th collides with the merchantman EDITH, sustaining this time quite serious structural damage, and she is Withdrawn from service and sent for for repair in a commercial shipyard.

In August she changes to Forth for repair completion at HM Dockyard Rosyth, going on by September and some trials in October. She resumled service and on the 5th, Carries out Degaussing tests at the Range. On the 16th she resumes trials with the Seafire, new version, and two days later with the lend-lease Avenger and Hellcats, prepared for deplyoment in the far east.
She also tests the last version of the SWORDFISH, ared wioth rockets and radar.
On the 23rd she carries out aerodynamic trials with the last version of the WILDCAT (FM-2) and on the 30th the amphibian SEA OTTER, successor of the Walrus, follows suite.
By November she is used as Target for torpedo attacks by RAF BEAUFIGHTERs, normally based in the Channel and operating on the North Sea.
On 6 Novembern, she trials the FIREFLY, replacement for the Fulmar. On the 13th, it’s the BARRACUDA, monoplane replacement for both the Swordish and Albacore.
On the 21st this time she tests a regular land-based SPITFIRE fitted with Hooks top evaluate a possible rapid conversion kit.
In December still in the Clyde she is Withdrawn from service for a machinery overhaul in Belfast Yard.

By January 1945 she is moved to Glasgow’s civilian yard for completion of overhaul, until March, followed by trials duties in the Clyde through April, also starting catapult trials and with the objective to test Tail Down launches. In May she tests night landings, and various deck lighting configurations and improvement. Many new technique are developed to be used in the Pacific by the BPF. There are discussions to send her in Australia to be closer to the operations, and by July she is sent to berthing but eventually not prepared or deployed.
Instead, she is nominated for “special trials” evaluating a carrier use of the new METEOR jet aircraft, and she is to be given a new, improved flight deck lighting for night landings.
Meter tests started on the 11th of August, with a modified model with hook (performed by legend of aviation test pilot Eroc “Winkle” Brown).

She also saw the same Brown landing for the first time a lebd-lease Bell Airacobra Mk. 1 on her flight deck, which was the second “first”, after the jet, there, first aircraft with a tricycle undercarriage, and she is also to be tested with the rubber deck for emergency landings planned for future carriers. She also tests first ever landings and take-offs by a glider (John Sproule) on a Slingsby T.20, and researching “round-down” turbulence.
She made further trials at night, using improved flight deck lighting to establish and by September 1945, she was transferred to Portsmouth Command and later on the 11th, pressed for a refit by HM Dockyard. By October she is at Portsmouth and Future deployments are under consideration, but December she is to be refitted if it’s the case but with a reduced crew due to the end of Conscripted service.
Thus in January 1946 she still awaits her fate at Portsmouth. Eventually the Navy decided to get rid of her, she is placed on the disposal list, negotiations started with her former owner, Union Castle to see the feasability for a return to trade.
Agreement is found and on the 26th she is sold and taken into convertion back to her former self. Fortunately, most of her formaer accomodations were kept. The superstructures had been “landed” and stored away so reconstruction is fast, which motivates the company instead of replacing her anew.

She sails from Portsmouth with a skeleting Steaming Crew to Belfast for handover to the company and on Februart 1946, the reconversion commenced with the removal of admiralty equipments. By March completion of de-storing to Belfast is done and she is paid off on the 21st for good, the returned officially the same day to Union Castle, conversion followeed as a passenger liner.

It’s on the 11 August 1945 that, she moored on the Clyde, she saw the first deck landing on a Gloster Meteor. These inaugural trials led to more jet flight trials on other carriers. However by that time the RN saw her too limited top operate jets and too small to be useful. This was the main reasons she was put on the disposal list and proposed to her former owner.
She was rebuilt to her original specifications, refreshed and modernized, but renamed WARWICK CASTLE as a new mail liner under construction at the time was to be named Pretoria Castle. The new liner had Accommodations for 180 first class and 335 tourist class passengers. Commercial service resumed on 13th March 1947, and she served on the Cape mail run (to south Africa and back), until larger ships replaced her and she was swapped to the ’round Africa’ service. On 26th July 1962, after being stricken by Union castle Line, she arrived at Barcelona for scrapping.

Read More


McCluskie, Tom (2013). The Rise and Fall of Harland and Wolff. Stroud: The History Press.
Lloyd’s Register of Shipping (PDF). London: Lloyd’s Register. 1939.
“HMS Pretoria Castle Gun 10 X BR 20mm 70cal Mark V VC Power Twin”. NavHist. Flixco Pty Limited
Mason, Geoffrey B. “HMS Pretoria Castle (F 61) – Escort Aircraft Carrier”. Service Histories of Royal Navy Warships in World War 2.
Osborne, Richard; Spong, Harry & Grover, Tom (2007). Armed Merchant Cruisers 1878–1945. Windsor, UK: World Warship Society.
Brown, Eric. Wings of the Weird and Wonderful, Wings on My Sleeve. Weidenfeld & Nicolson.
Drury, Tony. “A history of HMS Pretoria Castle”. Royal Navy Research Archive.
Helgason, Guðmundur. “HMS Pretoria Castle (F 61)”.
“UK/Union Castle”. The Late, Great Ocean Liners.


on royalnavyresearcharchive.org.uk
http://www.lategreatliners.com unioncastle.htm
shipsnostalgia.com/ hms-pretoria-castle.363378/
photo on iwm.org.uk/
on uboat.net/
on navypedia.org/
on willingale.me/
on flickr.com
on naval-history.net/
on naval-history.net

Model Kits

on worthpoint.com 1:250-ship-model-hms-pretoria-castle-269983251
on bob.plord.net/
Reference: Profile of the new liner bearing her name in 1955


HMS X1 (1923)

HMS X1 (1923)

Cruiser Submersible 1921-1937:
WW2 British Submersibles:
X1 | Odin | Parthian | Rainbow | Thames | Swordfish | Porpoise/Grampus | Shark | Triton | U class | T class | S class | A class

Nearly bankrupted by the war and in peace mood, Britain was not willing to engage in military innovation in 1920. Nevertheless, the Royal Navy on a limited budget could still experiment and based on the German project U-173, and the war prize U-141. This was designed HMS X.1 in utter secrecy. Massive and unwieldy this the Royal Navy’s only attempt to design such ship for possible merchant raiding, thwarted from the start by the Washington treaty’s ban on these. Having spent her purpose, she was scrapped even before World War II and largely escaped notice of naval analysts and historians since. But the she remained Britain’s largest submarine for 40 years. #royalnavy #interwar #cruisersubmarine #britishsubmarine

Origins and Genesis

HMS X1 was an experimental cruiser submarine designed for the Royal Navy, a merchant shipping raider. At the time of her launch, she was the world’s largest submarine. The name was later resurrected by experimental midget submarines designed to sink Tirpitz in Norway.

The idea of a submarine cruiser went from as early as 1915, but was not really started -with the mitigated experience of the M class- from 1921. This prototype, rightfully called “X-1” was a close “replica” of the projected, but never completed German U-173, a large U-kreuzer displacing more than 2,000 tons and armed with heavy guns. Indeed, in 1916 already the Kaiserliches Marine ordered the U-139 class, which was put into service as a large, long-range “cruiser submarines” or “U-Kreuzer”.

They were given two single, unshielded 15cm deck guns assorted with a precision rangefinder placed in an armored conning tower. Thus they were perfectly able to inflict substantial damage on any ship while surfaced, while keeping a large reserve of torpedoes for a long campaign partly submerged. After the war Germany was forbidden by the Versailles Treaty to built or operate any submarine and the few U-139 class boats were divided among the Allies. They were carefully studied, leading these to also experiment with this concept for their own information rather than to apply for any doctrine at the time.

The “Project 46” Boats were 300 ft, 2,483 t submerged behemoths. They were enlarged and tailored (for military purposes) versions of the Deutchland unarmed transport sub that made two trip to the US and back in 1916, and was armed in 1917, leading to the development of the U-151 class. Germany had many of such “U-Kreuzer” projected or in construction when the war ended in November 1918.
Read about WW1 German submarines. See also Project 40 steam U-cruiser

So, back to the U-139 class, France obtained U-139 (Schweiger, renamed Halbronn) which inspired the Surcouf (as the X1). U-140 (Weddigen) to the US, sunk as a target, and of course U-141 to Britain, tried extensively until BU in 1923, by the time HMS X1 was in construction. The previous year, the Washington Naval Treaty did not banned submarines (to the relief of France and Italy) but prohibited their use against merchant shipping. Thus, the initial purpose of X1 was being no longer valid, she was redesigned to engage against destroyers and frigates as a long range escort boat.

X1 came was by all purposes and intents Britain’s first experimental raiding submersible cruiser, when work started before 1921. It was largely based on the uncompleted German U-173 class of which plans were obtained by the admiralty, as a war prize. Plans were drawn by the sixth Director of Naval Construction, responsible for the majority of Royal Navy submarine classes in the Great War, designer of the X.1, which was Sir Arthur W Johns (1873-1937).

X1 was laid down on 2 November 1921 at Chatham. Secrecy surrounded the project at any level, the government preventing leaks, confiscating pictures and put on watch all newspapers. In the end, the launch could not be hidden and of course generated a massive publicity round the world.

Final Design of the X1

The final boat diverged of course from U-173 (Project 47?) in many ways. Information is very scarce if not inexistant on this class, which was planned to be completed between the summer of 1918 and January 1919. Due to the inability to find any blueprints of these (which were interned in UK and placed under high secrecy) we can only guess the X1 was a pretty close interpretation, varying only in details.

Hull and general design

The X1 hull was composed of a thick pressure hull, diameter 19 feet 7.5 inches, divided into 10 watertight compartments containing ballast tanks and fuel tanks. It was built to 1-inch thick (25 mm) to enable greater diving than any other model to circa 500 feet (150 m) which set a world record. Later reduced to 350 feet (100 m) for service. This internal hull was inside a wide external hull, which beam was calculated to give the main artillery good stability, and which contained the main ballast tanks and fuel reserves.
The hull ratio of 360 for 29 feets made for an almost 1/11 ratio favourable for speed, but there was enough buoyancy and with the flat section over the main ballasts to ensure a relatively predictable rolling.


Propulsion comprised two main MAN 8-cylinder diesel engines which developed 3,000 HP and two auxiliary diesel engines (rated 1,200 HP) from a war prize, U-Kreuzer U-126. When diving, the two 1,000 HP electric motors powered by three batteries groups reached 70 tonnes, an unprecedented load for an electric auxiliary power unit, and this ensured both a quick dive and great speed and range underwater, which was also unprecedented for TN submarines.


Her armament was really unique and stayed son but perfectly in line with the original U-Kreuze project. It consisted in two twin turrets forward and aft of the conning tower.
Each sported a very unusual ordnance, a pair of 130 mm (5-in) guns with a range at maximal elevation of 15,000 m. For better accuracy they were provided data from a large rangefinder installed on the bridge. No AA gun was planned, as it was still unusual in 1921. Would X.1 had been kept for service in WW2, it’s likely the conning tower aft would have been managed as a gun platform and a 2-pdr Pompom installed, or a quad Vickers LC-HMG 0.5-in mount.

Main Battery: Four 5.2 in guns (1924)

These 5.2″/42 (13.2 cm) QF Mark I were absolutely unique to X.1. They were never featured any any other ship in the Royal Navy. In fact they were specifically developed from 1921 for the new boat.
The concept was to create two lighweight, but fast-firing guns which can rapidly disable a destroyer at 6,000 yards (5,500 m), before the latter could engage the submarine with its own artillery, and later its own torpedo tubes. In practice the rangefinder was installed way too low to be of some use. Despite the large hull, the rolling nature of a submarine make it an awkward gun platform, unsteady. The guns were created almost from scratch in a hurry to equip X.1 in secret, and considered reliable after the teething problems were solved in its development.
Ihis was a standard ordnance made by Vickers Armstrong Elswick, from a patered inner A tube and partial jacket plus breech ring. It used a horizontal sliding and hand operated breech block using semi-automatic opening for speed, and only six of these were ever manufactured, the four to be installed and two spares.

Performance-wise, it was fast, with a nominal rate of Fire of 6 rounds per minute. It fired a separate HE round weighting 70 lbs. (31.8 kg) with a 10.78 lbs. (4.9 kg) MC 16 propellant charge, aor 11.36 lbs. (5.2 kg) SC 109 one. Muzzle Velocity was average, 2,300 fps (701 mps), but sufficient to deal with the weak protection of destroyers.
X.1 carried 100 rounds per gun, so 400 total. Max range was on paper 17,288 yards (15,800 m) at 40°. The turrets themselves were peculiar also. They comprised an ovale type platform on top of short, waterproof barbettes communicating to the respective ammo chambers below. The rear of the “bathtub” was open-air and only the forward part were protected, by a light snrapnel-proof hemispheric structure, creating unique “semi-turrets”. To cope with the ammunition consumption and balance the weight, Special ballast tanks were fitted to compensate as the ammunition was fired. Also the gun crew was considerable, 58 total, making for more than half of the full complement of 109.

Torpedo Tubes

The battery comprised six standard 21-inches torpedoes tubes, all in the bow. These six forward torpedo tubes were gathered from a cancelled late order WW1 L-class submarine. They fired the standard British Whitehead pattern 21″ (53.3 cm) Mark IV*. It was powered by wet-heater, Weighting 3,206 lbs. (1,454 kg) for 22 ft 7.5 in (6.896 m) long and carrying a 515 lbs. (234 kg) TNT warhead. Range/Speed had three settings: 8,000 yards/35 knots, 10,000 yards/29 knots and 13,500 yards/25 knots. It is not known how much reloads they carried, but given the boat’s size, we can assume perhaps two reloads per tube (18 torpedoes).

Author’s profile reconstructed from various sources
See this nice colorization and this one or these ones.

⚙ specifications

Displacement 2,780 long tons surfaced, 3,600 long tons submerged
Dimensions 363 ft 6 in x 29 ft 9 in x 15 ft (110.8 m x 9.1 m x 4.6 m)
Propulsion 4 MAN diesel 4,200 bhp (3,100 kW), 2 electric motors 1,000 bhp (750 kW)
Speed 19.5 kn (36.1 km/h) surfaced, 9 kn (17 km/h) submerged
Range Surfaced: 12,400 nmi (23,000 km; 14,300 mi) at 12 knots, Submerged: 50 nmi at 4 knots
Test Depht 350 ft (110 m), max theoretical 500 ft (150 m)
Armament 6 × 21 inch (533 mm) bow torpedo tubes, 2×2 5.2 in (132 mm) guns
Crew 111 (11 officers and 100 ratings)


Built at HM Dockyard, Chatham, the Royal Dockyard, behind high walls and armed guards in patrol, with blueprints locked under key and guarded after the workday, X 1 was laid down on 2 November 1921, launched on 16 June 1923 and completed on 23 September 1925. A rather long construction time, twice as much as the late-war L class.
This was explained by the interpretation of German plans and the unique nature of this new “boat”, carrying with it a number of technical challenges. She was indeed the most ambitious and complicated submarine in the Royal Navy, and the world’s largest at the time. The only ones that arrived close with the short M1 serie of 1918.

Thus, X 1 was commissioned at last in December 1925, make her sea trials and initial tests, including a diving test. It showed she was slower than expecting, with 2 min. 20 seconds to disappear below the waves, more than expected. In 1925 this was acceptable, not in 1936. Already her sea trials dragged on. The main issue was her diesels. Although they procured a record 19.5 knots and a long range, they broke out constantly. There was no easy fix and only time the machinery crew enough confidence to maintain a steady regime until she was declared operational, by April 1926.

As soon as she was deemed ready for service, X1 left for Gibraltar. Upon arrival however she needed fixes as the machinery crew was still not accustomed to manage the German main diesel engines, which caused troubles. Once her engines were repaired locally, then she resumed training. And in one of these sorties, she broke her starboard camshaft driveshaft while making a fast run, in January 1928. And this was just one scores of mechanical problems experienced that year alone.
Not of great use for the Mediterranean Fleet until the, the problems accumulated and became so acute that in 1928 she was sent to the Malta Drydock for long repairs as well as an overhaul. It was her “composite German propulsion” that was cited as the main issue.

She was not popular with her crew either, criticized for her too cramped living spaces despite her generous size. As said by her commanding officer: “internal arrangements not satisfactory because of overcrowding with auxiliary machinery, accommodation cramped, poor ventilation and humidity”. It was perhaps the result of a very large gun crew. She served again in 1929-30 but her main and auxiliary engines continued to break down constantly, marring all her trials and training. By the fall of 1930, HMS X1 was considered a failure. She was retired in 1930, and placed in reserve. The admiralty, based on the very poor reviews given in reports estimated a replacement or a redesign. She was kept in reserve from 1932-33.

Then, she was mothballed for more years, pending her fate. Eventually it was estimated that her concept was no longer filling any need in the RN and her mixed nature was decidedly an original problem that was too great to overcome. A rebuilt in this context was judged too costly. The crew was “recycled” in other subamrines rapidly. Eventually in 1936, she was discarded and formally decommissioned, after years in reserve.
She was eventually sold to Pembroke Yard in Wales on December 12, 1936 to be scrapped. With only three years of active service marred woth constant issue and overall bad reviews.

In effect, X 1 “cured” the category of submarine cruisers in the Royal Navy for ever. Despite of this, other nations still trusted the concept or were willing to have a try. These were the US, France and Japan. The first two went through the same rabbit hole, for slighlt different reasons, but the French Surcouf was probably the closest to X 1. the US produced three “cruisers” actually and multiplied blueprints after WWI (this is a topic that will be likely seen here in 2024). These were USS Argonaut (launched 1927) and the Narwhal class (1927 and 1930); They displaced between 3,900 and 4,000 tonnes submerged, so even more than X 1, but were armed with simpler deck guns, albeit 6-in/53 ordance, far above the norm for a US submarine. They were also considered as “white elephants” and still found some utility in WW2, as “spec ops” submarines in a serie of behind enemy lines operations.
Surcouf was largely inspired by X 1, launched in 1929. She carried a pair of 8-in guns, beating the competition, coupled with an observation floatplane. But she was also riddled with issues. She found not more succession or was hard to fit in, and remained for her value in film propaganda of the time. She was lost in the gulf of Mexico in 1942, in unclear circumstances (likely after a collision).

Only the Japanese fully embraced the concept.
They made the “cruiser submarine” an operational type of itself, with a doctrine attached, and produced several successive classes, such as the 4,700 tonnes four “1st class” seaplane carriers of the AM class, the two SH class (4,300 tonnes) and the massive STO class designed to attack the Panama canal (6,500 tonnes). The latter remained the world’s largest submarines until nuclear ones of the 1960s.

Despite of its lackluster career, X1 remained highly influential. She is a paradox. When British diplomats attempted to outlaw submarines as commerce raiders, the Admiralty was meanwhile building in full secrecy the ultimate corsair submarine, capable of destroying entire convoys and their escorts. She was “the first” of a new breed, publicized by the press as the “Royal Navy’s dreadful secret weapon in case of war”, so valuable for morale, and having an indisputable impact on other nations, while resulting in additions in the Washington and London treaty to try to forbid them.

Read More


X1, the Royal Navy mystery submersible by Roger Branfill-Cook.


scribd.com/: X-1-The-Royal-Navy-s-Mystery-Submarine
nmrn.org.uk (submarine-museum site)


Model Kits

kit review in klueser.de/

Minenräumboot (R-Boote)

Germany (1929-45) – About 424 Minesweepers

The Räumboote, or “R-Boote” were the mass-produced wooden-built German coastal minesweepers. In time, they also performed other missions, notably escort, ASW patrol and rescue. They were built from 1929 with the following R1, R17, R25, R41, R130, R151, R218, R301 and R401 classes, the latter mostly not completed at end of the war. In total, the Kriegsmarine operated 424 R-Boote from Lürssen, Bremen-Vegesack, Abeking & Rasmussen, Lemwerder at Schlichting. They soldiered in the Baltic, Norway, Channel and German bight, Mediterranean and Black sea, distributed among 19 flotillas. 140 surviving boats of the Räumboots-Flottille were used postwar by the Mine Sweeping Administration (GMSA) predecessor to the Bundesmarine. #ww2 #kriesgmarine #rboote #raumboote https://bit.ly/3AbPFbV

The German light minesweepers of WW2

“M-Boote”: The large fleets of WWI minesweepers were stil active in WW2. here, three M-Boote in 1938.
Germany was serious about mine warfare in WW1, but commenced late. The first dedicated minesweeper only appeared in 1915: It was the M1 class, of which 26 were built, followed by the 30 of the M27 and 30 of the M57 classes, judged os such quality they were almost all still in service in WW2, but also was interested in built cheaper, mass-produced motor minesweepers (MMS) for coastal operations. The FM type (66 boats in 1918-19) and F Type (1915-18, 75 boats) were seconded by the experimental LM boats (1917-18) which are the true ancestors of WW2 R-Bootes.

The Reischmarine’s Räumboote concept

F38 Motorboot 1917

The idea of building R-Bootes, or Räumboote (minesweepers), designed as moderately light boat for coastal operation was an idea driven by WWI experience, showing the intensive use of sea mines revealing the need for specialized boats alongside the larger and coastlier M-Boote built en masse. To deal with many minefield laid in coastal waters and aroud inlets notably in the gulf of Finland, other, light shallow-draught boats were needed, more suitable than M-Boote, tailored the high seas.
At first, converted boats such as tugboats and fishing vessels were primarily used to clear mines in the foreshore. From 1915, the Imperial Navy developed the motor “F-boats” (shallow mine clearance boats) for shallow mines as indicated, something that was sorely lacking. These were the real forerunners of the R-Bootes.

True ancestors: The “F-Boats”

The F-Boats were built from 1915 and until 1918, to an extent of 75 boats. They were alight wooden-hulled designisable for harbour duties and deployed from specially modified depot ships, the converted ex-pre-dreadnoughts SMS Wittelsbach, Schwaben, Preussen, and Lothringen. When deployed they acted as advanced bases and main defensive platforms as well. Of these 75 boats completed, only one was lost by a mine explosion. After the war they served for harbour and riverine duties under the Reichsmarine, Police and Riverine patrol. 12 were also sold to Belgium, still around in 1940.

The interwar birth of Mine Hunters

After the First World War, the Reichsmarine had to clear sea routes in the German area of responsibility for mines. In the winter of 1919/20 alone, over 100,000 mines were cleared. They were mostly anchored mines, but in view of newly developed or under development mine types, such as ground mines, magnetic field mines, electromagnetic mines, acoustic mines, etc., special boats were required. They were restrospectively the first “mine hunters”, built as non-magnetic as possible, manoeuvrable and not too large for use in coastal waters.
The Räumboot type was born, the initial design task was given to Abeking & Rasmussen (A&R) shipyard in Lemwerder, Netherlands, in the 1920s, to conceal the activity from the Versailles treaty commission. The first boats were built in 1929-1934 (R 1-8) by Lürssen and A&R (R9-16). They were unarmed at the time and could be “sold” to inspectors as harbour duty ships, or just for their intended purposes and contribute to the clearing of sea mines.

An Innovative Type, a-magnetic and with VS drive

The type supplied by the two shipyards largely corresponded to the requirements of the Reichsmarine and they were mostly built of wood, some like R 8, and R 17-24 provided with the new Voith-Schneider drive (VS): The latter’s principle was strikingly simple: The magnitude and direction of thrust can be set steplessly, using circular disk with movable and controllable blades installed at a 90 degree angle for the disk to rotates at the vessel bottom. The magnitude of thrust is determined by the rotational speed of the disk and blade angle determines the direction of thrust. For these R-Boote, they were horizontally mounted propellers, perfect for precise maneuvering even under adverse conditions. But these were complex systems which were in short supply.

Voith-Schneider System

As the result, these interwar R-Boote were very manoeuvrable and powerful in order to give the clearing gear the required pulling power. The demand for non-magnetic materials for the engines however could only be realized after the Second World War. The Bundesmarine Schütze-class fast minesweepers were the first totally a-magnetic minehunters built in the world. However, the the WW2 boats were equipped MES system (a kind of degaussing system), greatly reducing the magnetic field.

Gradual Improvement

The first boats displaced 60 t and were made of composite construction (steel frames with wood planking) with MWM diesel engines developing 714 hp acting on two propeller screws, or Voith-Schneider propellers.
Next came the R 17-24 (all by A&R) with 115 t displacement and 1836 hp in the years 1934 to 1938, so assigned to the Kriegsmarine, which naval staff did not developed a strong interest for these, but rather preferred to concentrate on the S-Boote.
R 25-R 40 were boats of 110 t displacement, with class screw propeller drive built in 1938/1939. They were all provided with an air-cooled Deutz diesel generator providing electricity for clearing magnetic mines, installed in a housing on the upper deck. These were the first “magneic mine specialists”. For this serie, it was looked at using them in a more offensive way, notably fitting them with mines, inclusing magnetic ones, since they were the right kind of boat to lay them with safety.

As the Second World War grew near, the construction program was greatly expanded. A grand total of 424 Räumboote were built based on the same predecessor type. The majority had conventional propellers due to production bottlenecks notably for the VS system, and due to a lack of armament-related. R 41-150 received VS propellers anyway. Shipyards responsible for this wartime production were A&R Lemwerder, Burmester shipyards (Bremen) and Swinemünde as well as Schlichting shipyard (Travemünde).

R-Boote Tactics


The R-boats proved to be extremely robust and versatile. Apart S-Boote, already well budy with the Torpedo tasks, the lack of fast, large motor boats soon had the Räumboote providing tasks during the war for which they were never intended: They were used to secure convoys, minelaying, ASW patrols, escorting U-boats in and out of their bases and sea rescue, both for the Kriegsmarine and Luftwaffe.
The tactics were simple, originally they were intended to serve in small squadrons of six boats, but were to be assisted by an armed depot ship/tender. Ideally specialized, a bit like the pre-dreadnought depot ship concept of 1918.
However these specialized R-Boote depot ships fell short due to arbitrations in the Kriegsmarine. Large, well armed and modern dedicated depot ships were assigned primarily to U-Boats (Saar, W. Baer class and converted merchant ships) and others to the S-Bootes (Tsingtau, Tanga, Lüderitz, Nachtigal classes).

In the end, since they were coastal boats, they were assigned larger minsweepers: Von der Groeben, Alders, Raule, Juningen, Nettelbeck, Von der Lippe, Brommy, Hille were all ex-minesweepers of the WWI series. Nordpol, Nordsee, Gazelle, Nadir, Schwertfisch, Weser, Barbara, Rigel, were very diverse ships which were essentially “what was available”, and with time in 1943-44, some unit operated without a tender/escort at all.

A flotilla of R-41 class boats advancing at high speed, apparently for submarine hunting, as the boat in the foreground has an additional pattern of depth charges on its foreship (shipsnostalgia).

Gazelle was the last former WWI cruiser, Barbara was a Flakschiff (Former Belgian Zinnia), Nordsee/Nordpol were 1914 tenders…
When deployed at sea, the depot ship stayed behind, operating long range-communication with the HQ and defense based on its better armament, but also providing spares and supplies for the R-Boote. A minesweeping operation was in general a 24-hours affair at the most depending of the technicity of the mines and size of the minefield.


From the quay wall of the French port of Royan, the marine gives flag signals to the German Räumboote lying in the roadstead. Oct 1940
PK-Horster-Scherl picture service

The first 16 small pre-war boats built were transferred to the Mediterranean (RF 12) by inland waterways and overland, but none survived the war. Some by the same paths found their way into the black sea fleet (RF 30), and operated alongside the Romanian Navy until the Soviet counter-offensive drove them out. Some units served in the Baltic, close to still Soviet-held ports and made riverine operations when possible. Others operated in the German bight, the channel, and around north sea sandbanks, as well as around Heligoland and from Norway. There was also unit dedicated to training (RF 17), with more than 400 R-Boote in service, this was quite necessary. Because of their light armament, many were destroyed or damaged during wartime.

Wikimedia commons photo showing the deployment of a R-Boote in shallow waters.

One interesting use was from the narrow fjords of occupied Norway. In October 1940 the unit commanding officer, Kapitanleutnant Hans Bartels, commissioned the construction of his twelve own highly successful small vessels based on Norwegian fishing boat designs, called Zwerge (‘dwarves’). The unit was later called ‘Tigerverband’ based on their pennant bearing a snarling tiger’s head over crossed swords. Later sporting small commemorative pins awarded with a special certificate. High command eventually condemned the initiative and Bartels was relocated on the destroyer Z34.

The Vorpostenboote (‘outpost boats’) recouped many of these units tasked of patrol work, creating outer protective screens for convoys and port guards. At first former whaler, trawlers, captured boats, they were spread into 33 Vorpostenbootflottillen, operating in the Baltic, Denmark, North Sea, France, Holland. They were considerably reinforced during the war as Civilian yards were requitioned and put under the authority of the Kriegsmarine to resume production. The new civilian fishing boat designs were sometimes heavily armed and redesignated as “Kriegsfischcutter” and could also be outfitted for minesweeping and ASW duties. They served alongside, and completed the numerous R-Boote.

As for ASW duties, if very few of the dedicated U-Jagd Boote were specialized vessels in U-Bootsjagd Flottillen, the bulk of operations were made by mixes of R-Boote type minesweepers and the VP-boats see above. The Kriegsmarine still drafted its own specifications for further dedicated sub-hunter, but shipyard priorities decided otherwise. In the end, only the M35 minesweepers were the closest to this type ever. However in this role, the R-Bootes lacked proper sonar and depht charge reserves for effectively chasing submarines.

Note that R-184 was captured by the RN and duly examined, leaving a report in 1942 (see later pdf in the sources). Here are two plans, showing the boat plan by British intel, and a scheme of minesweeping operations as reconstructed after interrogating the crew and examining the gear.

Succession: MV-Boote

Probably the most interesting development of the R-Boote type was the Mehrzweckboote or “general purpose boat”, by order of March 1943. It was a powerful, but slow boat with heavier armament. It was intended to replace the R-boats and VP-boats, weighted 290-ton for a 52m x 7.2m hull, single 6-cylinder diesel engine for 14 knots. Two torpedo tubes were fitted near the bow a bit like for S-boats, completed by two 8.8cm, a single 3.7cm two quad “Flakvierling” 2cm flak gun mounts. But of the 12 boats ordered at the Stiilcken yard in Hamburg, only MZ1 was completed before the end of the war. Construction in pre-fabricated sections was envisioned. If MZ1 was launched on 16 April 1944 and tested later that year, the industrial situation Germany was in by that time precluded any progresses. Apart MZ1, only three keels perhaps has been laid down and little work done, with foggy records to say the least, no photos or plans left.

Postwar Fate: GMSA

R Boote of the GMSA in 1952
140 survived the war, taken over by the allies. The USA received 48, the USSR 45, Denmark 24, Great Britain 11, the Netherlands 8 and Norway 4.
However they were used to form the “German Minesweeping Service” or “Deutscher Mienenräumdienst” after the war. 24 more were also returned to Germany to form Bundesmarine’s early minesweeper squadrons in 1956, used until the late 1960s. Others were passed on to other allies. Italy and Yugoslavia received some for example.
The German mine clearance Administration, replacing the Kriegsmarine, used these boats to clear the Baltic Sea, German Bight and Norwegian waters, Germany’s area of reponsibility to ensure trade safety. Some were handed over to the water police of Western federal states while R 406 was converted in 1948 as the passenger ship Arngast for island service in the Jade Bay and to Heligoland, became in 1951 the LSU (R 154) and Bundesmarine’s Naval Locating School OT 2, still active in the 1980s.

Indonesian Pulau-Rau class minesweepers in the 1960s

R-Boote Units

R-Boote based in the Netherlands, the 9. Räumboots-Flottille (rotterdam).

Between the wars and during World War II, a total of 19 Räumboots-Flottille (German for Minesweeper Flottiles) were created (plus one postwar). While most were disbanded at the end of the war or after the German surrender, a few were retained for use by the German Mine Sweeping Administration (German: Deutscher Minenräumdienst or “German Mine Sweeping Administration” or GMSA) and dissolved after the war. An additional flotilla was created in the immediate post-war period, also for use by GMSA1.

1. Räumboots-Flottille:
Established in octobre 1937: R 17, R 18, R 19, R 20, R 21, R 22, R 23, R 24. Other assigned boats: R 43, R 52, R 65, R 66, R 67, R 68, R 69, R 70, R 71, R 72, R 73, R 74, R 75, R 76, R 106, R 119, R 120, R 127, R 128, R 145, R 150, R 249, R 259, R 260, R 268. Escorts assgned: KMS Nettelbeck, Nordpol.

2. Räumboots-Flottille:
Established in november 1938, with the following boats: R 25, R 26, R 27, R 28, R 29, R 29, R 30, R 31, R 32. Other assigned later: R 74, R 77, R 84, R 86, R 113, R 114, R 116, R 125, R 129, R 169. In 1945, the unit was down to a single squadron: R 412, R 413, R 414, R 415, R 416, R 417. KMS Brommy (ex-M50/550) was their tender.

3. Räumboots-Flottille:
Established in 1939 at Pillau, with ship: R 33, R 34, R 35, R 36, R 37, R 38, R 39, R 40. Other later asssigned: R 163, R 164, R 165, R 166 R 196, R 197, R 203, R 204, R 205, R 206, R 207, R 208, R 209, R 216, R 248. Escort and supply ships, KMS Von der Groeben, R-Boat tender. En 1945, the unit had the following: R 270, R 288, R 289, R 418, R 420, R 421, R 422 R 423 with KMS Gazelle as escort.

4. Räumboots-Flottille:
Created by april 1940, with the boats: R 41, R 42, R 43, R 44, R 45, R 46, R 47, R 48, R 49, R 50, R 51, R 52. Other assigned: R 80, R 83, R 115, R 120, R 126, R 128, R 138, R 143, R 150, R 218, R 240, R 243, R 244, R 245, R 246, R 255, R 262, R 274, R 275, R 290, R 291.

5. Räumboots-Flottille:
Created in August 1939 with the boats: R 1, R 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, R 12, R 13. In 1941, she was composed of the following: R 53, R 54, R 55, R 56, R 57, R 58, R 59, R 60, R 61, R 62, R 63, R 64. Other assigned: R 89, R 90, R 113, R 121, R 122, R 124, R 238, R 250, R 269, R 273. Escort ship: KMS Elbe.

6. Räumboots-Flottille:
Created in July 1941 at Cuxhaven, with the boats: R 9, R 10, R 11, R 12, R 13, R 14, R 15, R 16. Other assigned: R 1, R 3, R 4, R 6, R 7, R 8, R 115, R 187, RA 10 (former British MTB), and RD-boats: RD 116, RD 117, RD 118, RD 119, RD 120, RD 121, RD 122, RD 127, RD 128, RD 129, RD 130, RD 131.

7. Räumboots-Flottille:
Created in octobre 1940, with the following boats: R 151, R 152, R 153, R 154, R 155, R 156, R 157, R 158, R 159, R 160, R 161, R 162. Other later assigned: R 173, R 202, R 223, R 262, R 277. Eescort and tender ships KMS Weser.

8. Räumboots-Flottille:
Created in january 1942 with the following boats: R 92, R 93, R 94, R 95, R 96, R 97, R 98, R 99, R 100, R 101. Others later assigned: R 113, R 117, R 118, R 130, R 146, R 147, R 257, R 258, R 409. Assigned escort and supply ships: KMS Nadir, Schwertfisch.

9. Räumboots-Flottille:
Created in may–june 1942 in Rotterdam: R 85, R 87, R 88, R 103, R 104, R 105, R 107, R 108, R 109, R 110, R 111, R 112, R 131, R 148, R 149, R 247, R 251, R 412, R 413, R 414, R 415, R 416, R 417 Assigned escort/tender: KMS Alders.

10. Räumboots-Flottille:
Created in february-march 1942 in Cuxhaven. Assigned Boats: R 175, R 176, R 177, R 179, R 180, R 181, R 182, R 183, R 184, R 190, R 213, R 217, R 218, R 219, R 221, R 222, R 224, R 234. Assigned escort/tender: KMS von der Lippe.

11. Räumboots-Flottille:
Created by September 1939, with 8 armed trawlers and an escort. By October 1940 renamed 7. Räumboots-Flottille assigned to battered R-Boote which needs refit for service. From 1942 she is assigned the R 39, R 161, R 162, R 189, R 192, R 198, R 199, R 200, R 201, R 212, R 215, RD 102, RD 103, RD 104, RD 105, RD 109, RD 111, RD 112, RD 113, RD 114, RD 148, RD 149, RA 252, RA 253, RA 254, RA 258, RA 260, RA 261, RA 262, RA 263, RA 264, RA 267, RA 268. No escort ship.

12. Räumboots-Flottille:
Created in may 1942 at Bruges, Belgium, then reassigned to the Mediterrananean, dissolved in february 1945. Assigned boats: R 34, R 38, R 40, R 178, R 185, R 186, R 188, R 190, R 191, R 194, R 195, R 210, R 211. Escort/tender KMS von der Groeben.

13. Räumboots-Flottille:
Created on 15 november 1943 in the Heligoland Bight. In 1957, it was trasferred to the Bundesmarine, via the minesweeping administration. This unit operated the R 132, R 133, R 134, R 135, R 136, R 137, R 138, R 139, R 140, R 141, R 142, R 144, R 177, R 252. They were supplied and escorted by the KMS Nordsee.

14. Räumboots-Flottille:
Created in december 1943, operating in the Channel. After the French invasion in juin 1944 it was rassigned to the Jade and Heligoland bight, and Baltic sea. Assigned boats: R 18, R 214, R 219, R 225, R 226, R 227, R 227, R 228, R 229, R 230, R 231, R 232, R 233, R 235, R 236, R 237, R 242, R 259, R 263. Escort: KMS Barbara.

15. Räumboots-Flottille:
Created 1st July 1944 in the Baltic. These boats were also deployed in Finnish waters. Assigned boats: R 239, R 240, R 241, R 243, R 244, R 245, R 254, R 255, R 256, R 409, R 410, R 411.

16. Räumboots-Flottille:
Created in october 1944 at Haugesund, Norway, dissolvd 25 november 1947. Assigned boats: R 264, R 266, R 267, R 401, R 402, R 403, R 404, R 405, R 406, R 407, R 408, R 424.

17. Räumboots-Flottille:
Created in July 1944 for training R-Boote crews, as Räumbootsflottille zbV, based in the Baltic. Dissolved by late 1947. Assigned boats: R 55, R 71, R 102, R 167, R 170, R 174, R 175, R 176, R 181, R 220, R 241, R 246, R 249, R 290.

21. Räumboots-Flottille:
Created by july 1943, composed of 12 large escort minesweepers (Geleit-Räumbooten) based in Bergen, Norway. Dissolved early 1946. Assigned boats: R 301, R 302, R 303, R 304, R 305, R 306, R 307, R 308, R 309, R 310, R 311, R 312

25. Räumboots-Flottille:
Created in the summer of 1945 in Denmark she ships of various flottillas, by the German Minesweeping Administration, until early 1946. Assigned boats: R 18, R 23, R 65, R 234, R 254, R 257, R 258, R 409, R 410, R 411 with Riegel as escort/tender.

30. Räumboots-Flottille:
Created in june 1943 with Dutch captured minesweepers, reassigned to the black sea. Deactivated by August 1944: R 30, RA 51, RA 52, RA 54, RA 56.


The R-Boats, like the S-Bootes, and even perhaps more often, were camouflaged. Patterns were unregulated, left to the choice of Flotilla Commanders, although they had to apply at least a base pattern which was adapted to the theater of operation on coastal areas. It was the “broken line” pattern with black motives on a dull grey base. Some of the designs were relatively simple, “zebra like” and others were particularly complex, such as this one below.

To come in the future: Renditions of various classes and camouflage pattern designs.


As defined by the Reischmarine and confirmed later by the Kriegsmarine, light minesweepers were vital in the event of a naval blockade by the Allies. They were design to lead the way, and also for possible quick sweeps and or even stealthy minelaying. They were larger and much slower than the S-Boote and were considerably reinforced with AA guns.
They were sleek, low profiles, lightly-built, with shallow draughts for coastline use. Their metal understructure was completed by wood framing and they had rounded bilges built-in.

The typical powerplant was fixed around two flexible MAN marine diesels for an output of 1,836 horsepower each on under stern shafts and the VS (Voith-Schneider) system in some cases, a real advantage to manoeuver in minefields. Top speed was not stellar as they managed 17 kts in the best conditions, although the R301-R312 group was modified with a triple-shaft arrangement, enabling a 24 knots speeds. Still not S-Type level, but good enough for hard engagements.

They were also lightly-armed. The typical outfit in 1939 was a single turreted 37mm C/30 aft and two Rheinmetall FLAK c/38 20 mm cannons, up to six in wartime, plus several 7.92mm MG.34 light machine guns for close defense. Minesweeping apparatus was “classic” and derived from the WWI M-class, with however measured taken for improving their ability to defuse magnetic and modern mines of all types. They were also outfitted for minelaying, photos showing them carrying up to six on individual cradles aft, alternative to depth charge racks for ASW escort work. The R301-R312 boats even were fitted with two fixed broadside torpedo launchers (pointing forward), they were pressed especially in the Channel fleet were close encounters were frequent. The crew went up with time, as they received more armament, up to 38 in all.

R-Boote nomenclature

R 1 class (1929)

R8 at sea, interwar
The first group R1 to R16 dated back from 1929. These were small vessels of 26 meters, 60 tonnes with a composite hull, capable of 17 knots. They were still partly inspired by the WWI “F-Boote”. The hull was stepped, with an embeddeded main deck, more typical of service boats than classic warships. The superstructure however was fully enclosed. Armament was reinforced during the war, as by 1943 R1 had four 4 single additional 20mm/65 C/38, and a DCR (Depth Charge Rack) plus ten mines, as the folling boats of the R2 serie, including R8.
They were used as patrol, ASW and then rescue ships as the war progressd and new ships were made available. The prototype was created by F.Lürssen, still much inspired by the F type minesweeping boat of WWI.
R1 was badly damaged and a total constructive loss (CTL) on 24.11.1943. R2 was discarded in 1942, all the rest were lost in action or scuttled: R3 on 24.11.1943, R4 on 22.2.1945, R5 on 3.1.1940, R6 on 13.8.1943, R7 on 9.9.1943, R9 on 2.8.1942, R10 on 2.5.1945, R11 on 2.8.1942, R12 on 5.9.1944, R13 on 9.9.1943, R14 on 16.3.1945, R15 on 16.4.1945 and R16 2.5.1945.

⚙ R1 specifications

Displacement 60 tonnes (R8 63t)
Dimensions 26 x 4.41 x 1.21 m (85ft 3in x 14ft 6in x 4ft)
Propulsion 2 shafts MWM diesels, 700 bhp
Speed/Range 17 kts, 4tons oil, circa 800 nm/13 kts
Armament 1x 20mm/65 C30 FLAK, Minesweeping gear
Crew 19

R 17 class (1934)

R-Bootes in 1939, ONI photo
From 1934, the R17 group comprised 8 units, which displacement increased to 115 tonnes, for 37 meters in lenght and 21 knots in speed. They came from by Abeking & Rasmussen, and Schlichting yards, with a simplified “flush deck” hull and minimal superstructures. Their minesweeping gear could operate up to a force sea 6 on the Beaufort scale. During the war, in 1943 they rweceived two twin extra 20mm/65 C/38 AA guns and two single ones, plus a DCR. By 1944 the remainder earned a single 86 R Ag M42/43 AA Rocket Launcher. Most were built with the Voith-Schneider propulsion system also.
R17 was sunk by the Norwegian minelayer Olav Tryggvason, R19 by Allied aircraft, R20 by a German mine.

Profile and elevation of the R21

⚙ R17 specifications

Displacement 115 tonnes ()
Dimensions 27 x 5.50 x 1.30 m ()
Propulsion 2 shafts MAN diesels, 1,800 bhp
Speed/Range 21 kts, diesel oil 10.8 tons, 900nm/15 kts
Armament 2x 20mm/65 C30 FLAK, 12 mines, Minesweeping gear, see notes
Crew 17-27

R 25 series (1938)

R38, camouflaged, underway Src: http://www.lexikon-der-wehrmacht.de/Gliederungen/Sicherungsflott/R38-1.jpg
Nothing much to say, they were a repeat of the previous design, a bit larger and faster. R25 to 34 had a 1.40 normal draught, 1.42 deep load while R35-40 had a 1.51 deep load draft.
By 1943-1944 survivors were rearmed with a single aft 37mm/80 SK C/30 or or a 37/69 FlaK M/42 and two twin 20mm/65 C/38 AA guns plus one DCR.
Fate: R25 was surrendered in 1945 and transferred to Soviet Union 6.1946. R26, R28, 32 to Denmark 12.1945, R31 to UK. R27 was sunk 11.4.1944, R29 on 23.9.1943, R33 on 19.7.1943, R34 on 10.8.1944, R36 on 29.4.1943, R38 on 27.8.1944, R39 on 17.2.1944 and R40 on 7.3.1943. R35, 37 were scuttled on 30.8.19447.

FLICKR, 3D rendition (Gaijin Ent.) of the R25.

R29 plan drawing (FLICKR)

⚙ R25 specifications

Displacement 110/126 tonnes (FL)
Dimensions 35.4 x 5.55 x 1.40 m ()
Propulsion 2 shafts MAN diesels, 1,800 bhp
Speed/Range 23.5 kts, diesel oil 10 tons, 1100nm/15 kts
Armament 2x 20mm/65 C30 FLAK, 10 mines, Minesweeping gear, see notes
Crew 20

R 41 (mob) series (1943)

Preceded by the R25 series (1938-39, 16 units, 110 tonnes and 35.50 meters), the R41 mobilization series was heavier and more spacious. The last were put into service in 1943, they received as reinforcement two twin 20 mm mounts. 88 units were be built, making the bulk of the active flotillas in 1944.
They Displaced 125t standard, 135t Flly Loaded, and diverged in size: R41-10 measured 36.8 wl 37.8 oa whereas R102-129 were 36.8 wl 38.6 oa long, for 5.82m in beam and a draught of 1.40 normal and 1.51 deeply loaded. Some had the Voith-Schneider propulsion systems and they given either MWM (R41-48) or MAN diesels (R49-129) for 1,800 shp, 20 knots, a range of 900 nm at 15 kts based on 11.1 tons oil. They also diverged in armament. The first serie (R41-107, 109-111) had the original two single 20mm/65 C/38 guns and DCR but the second serie (R108, 112-129) received the aft single 37mm/80 SK C/30 or 37/69 FlaK M/42, three single 20mm/65 C/38, DCR, no mines. They had a crew of 30-38/ Later during the war, the early serie received alternatively the 37mm/80 SK C/30 or the 37mm/69 FlaK M/42, and all had two twin 20mm/65 C/38 where thir single mounts used to be. Sone has three single 20mm/65 C/38 or one or two twin 20mm/65 C/38 alternatively. Survivors in 1944 received the 86 R Ag M42/43 rocket launcher.

Same 3D rendition (Gaijin Ent.) of the R56.
R41 was sunk by British MTBs. R44, R51, R52, R56, R59, R72, R79, R80, R81, R84, R89, R92, R97, R111, R119, R123, R125 and R129 by aviation. R50, R73, R77, R78, R82, R86 and R109 in German minefields. R54, R64, R74, R93, R94, R95, R110, R114, R116 and R126 by Allied mines and R66 and R70 were sunk by Soviet mines. R60, R61 and R62 sabotaged in Helsinki, R69 and R106 were claimed by Soviet aviation.

R117 as built on trials (FLICKR)

In Bundesmarine Service:
Displacement standard, 135-130 tons, 36.8 wl 38.6 oa, Aldebaran, Algol, Altair, Pegasus, Wega, UW4: 36.8 wl 37.8 oa and Arkturus, Deneb, Skorpion: 36.8 wl 38.6 oa for 5.82m wide and same draught. 2 Voith-Schneider MWM/MAN diesels, same output, speed and range. As modernized thay had two single 20mm/80 Mk 7 (HS804), a revised mechanical minesweeping gear, hydrophone, radar and a crew of 27-34.

⚙ R41 specifications

Displacement 125 tonnes ()
Dimensions 37.80 x 5.80 x 1.40 m ()
Propulsion 2 shafts MAN diesels, 1,800 bhp
Speed/Range 20 kts, diesel oil 11 tons, 900nm/15 kts
Armament 1x 37mm/69 M/42 FLAK, 2×2 20mm/65 C30 AA, see notes
Crew 34

R 130 (mob) series (1943)

The 20 R130 type units, built at the end of 1943, were a little more spacious and slower. They also received 3 twin 20 mm AA mounts. They were armed as standard with a single 37mm/80 SK C/30 or a 37mm/69 FlaK M/42, two twin 20mm/65 C/38 and two single ones as standard, and some received as completed a 86mm R Ag M42/43 AA RL. They all had also a DCR for ASW patrols.
R131, R139 and R141 were sunk by Allied aircraft and R145 was torpedoed by a Soviet aircraft, lost also. Many others were damaged. There were survivors: in June 1956, Orion, Capella, Merkur, Rigel, Mars, Castor, Pollux, Sirius were recommissioned in the Bundesmarine after a modernization (notably sonar and radar) and in july Regulus, Spica, Jupiter, Saturn; in December UW5 were recommissioned. They served until the 1970s, although recoignised as too slow to deal with the latest Soviet SSNs. Instead they targeted small diesels subs like the Quebek class.

R-130-150 original plans, unfortunately i could only find the vignette.

⚙ R130 specifications

Displacement 150 tonnes ()
Dimensions 41.10 x 5.80 x 1.60m ()
Propulsion 2 shafts MAN diesels, 1,800 bhp
Speed/Range 19 kts, diesel oil 11 tons, 900nm/15 kts
Armament 1x 37mm/69 M/42 FLAK, 6x 20mm/65 C30 AA, see notes
Crew 38

R 151 (mob) series (1943)

KMS Algol, by Abeking & Rasmussen.
The R151 series of 1940-43 consisted of 68 smaller but faster vessels than those of the R41 series. In 1944-45 they received six 20 mm AA cannons as reinforcement. They were faster, and equipped with mines unlike the previous series. Later during the war they were reequipped with a single aft 37mm/80 SK C/30 or 37mm/69 FlaK M/42, two twin 20mm/65 C/38 and a single DCR, plus an hydrophone.
R151, R169, R188, R191, R193 and R204 were sunk by Soviet aircraft, R161, R186, R187, R190, R194, R200, R201, R208 and R215 Allied aircraft, R177 by a Soviet mine and R179 an Allied mine. R180, R184 and R192 were sunk by British MGBs in close surface combat.

Colorized R-Boat, src unknown, FLICKR

Modernized R-Boats used by the Bundesmarine, detailed plans from the Bundesarchiv

⚙ R151 specifications

Displacement 110t standard, 126/128t FL
Dimensions 35.40 x 5.60 x 1.40 m
Propulsion 2 shafts MAN diesels, 1,800 bhp
Speed/Range 21 kts, diesel oil 11 tons, 900nm/15 kts
Armament 2x 20mm/65 C/38 AA, 10 mines, see notes
Crew 38

R 218 series (1944)

R-218 scheme – Credits parow-info.de
This last series of the war (63 units completed out of 83 planned), built at the end of 1943 at the surrender, were fairly spacious, fast, and received three twin 20 mm AA mountings shortly after their completion, making them the most heavily armed type. The 1944 S401 series was to include 23 units, never completed. R239 experimented 2 KHD diesels for 2400 shp.
As completed they had a single 37mm/80 SK C/30 or 37mm/69 FlaK M/42, three twin 20mm/65 C/38 or three single ones and 12 mines plus a DCR and hydrophone.
R218 was sunk by British MTBs and R219 by the same, but finished off by aircraft. R221, R232, R237, R239, R250 and R261 were sunk by Allied aircraft. R222 due to a Soviet mine. R224, R227, R243, R256 and R260 by Soviet aviation, R231 disappeared without a trace. R272, R273, R274, R275 and R276 were never completed and destroyed on their slipway by Soviet aviation. 6 boats were transferred to East Germany and used by the GDR police postwar as R1-6 from May 1950, discarded 1956. R266 was attributed to the USA and sent back to the Bundesmarine in 1957 used as the border guard ship TS AT1.

⚙ R218 specifications

Displacement 140t standard, 148t FL
Dimensions 39.40 x 5.72 x 1.50/1.61 m
Propulsion 2 shafts MWM diesels, 2,500 bhp
Speed/Range 21 kts, diesel oil 15 tons, 1000nm/15 kts
Armament 1x 37mm, 6x 20mm/65 C/38 AA, see notes
Crew 40

R 301 (mob) (GR) series (1943)

The 12 units of type R301 were larger and designed as escorts of the first, with two torpedo tubes. However they were completed far too late to be pressed in the Channel fleet as expected and ended in the Baltic. They were the heaviest of the serie, with three shafts, reaching almost 185 tonnes fully loaded. But also the fastest and with the better range and armament of all series.
R313-R320 built in Abeking & Rasmussen, Lemwerder were cancelled on 12.1943.
Basic armament comprised a single 37mm/80 SK C/30 or 37mm/69 FlaK M/42, three twin and a single 20mm/65 C/38 mm AA alternative to two twin, one single, and two 86mm R Ag M42/43 AA RL plus two 533 TTs and 16 mines as well as their mechanical minesweeping gear, DCR and hydrophone, making them pretty well-rounded, versatile ships called GR (Geleit Räumboot).
Many were never completed, R301 and R306 were sunk by Allied aircraft and R304 hit an Allied mine. The rest were scuttled in 1945, or surrendered in 1945, being attributed to the US and Soviet Union.

⚙ R301 specifications

Displacement 175t standard, 184t FL
Dimensions 36.8/41 x 6 x 1.80/1.88 m
Propulsion 3 shafts MWM diesels, 3,750 bhp
Speed/Range 23.5 kts, diesel oil 15.8 tons, 716nm/20 kts
Armament 1x 37mm, 7x 20mm/65 C/38 AA, 2 TTs, 16 mines, DCR, LR, see notes
Crew 40

R 401 series (1944)

The last R-Boote serie, started way too late into the war to be completed on time. They had more powerful diesels, enabling for the gretest speed of all series, 25 kts. The immense majority of the initial order was cancelled, and the remainder ships were captured on slipways by Soviet or US troops. The only one operational, R402, was sunk by Allied mine on 22.12.1944. R406 – 408 were recommissioned by border guard in 1956-1957 and modified: UW6, AT2, OT1 had a single 20mm/80 Mk 7 AA gun only. The remainder were either BU on slip or attributed to the US/Soviet Union.

⚙ R301 specifications

Displacement 140t standard, 150t FL
Dimensions 36.8/39.4 x 5.72 x 1.50/1.65 m
Propulsion 2 shafts MWM diesels, 2,800 bhp
Speed/Range 25 kts, diesel oil 15 tons, 1000nm/15 kts
Armament 1x 37/69 FlaK M/42, 3×2 20mm/65 C/38, 2x 86mm R Ag M42/43 AARL, 12 mines, DCR, hydrophone
Crew 37

Src/Read More


Köhlers Flottenkalender 1960 und 1961
Erich Gröner: Die Schiffe der Deutschen Kriegsmarine und Luftwaffe 1939–45. Lehmanns Verlag, München 1954
Hans Mehl, Knut Schäfer: Die Seestreitkräfte der NVA. Motorbuchverlag spezial, 2004
Conway’s all the worlds fighting ships 1922-47


“Räumboots-Flottillen”. Lexikon der Wehrmacht
german-navy.de r-boat
Gröner, Jung, Maass U-Boats and Mine Warfare Vessels
R-Boote on military-factory
Hitler’s Armed Forces Auxiliaries: An Illustrated History.
Hervieux, Pierre German Motor Minesweepers at War 1939-1945
R 184 Interrogation of Survivors, 1942 report, pdf

Model Kits

R3 series on scalemates.com
britmodeller.com/ r25-class
3d rendition, artstation See also (“12th man” movie)

HMS Unicorn (1941)

HMS Unicorn (1941) – Repair Aircraft Carrier

Royal Navy – 1939-59

WW1/WW2 RN Aircraft Carriers:
ww1 seaplane carriers | Ark royal (1914) | Campania | Furious | Argus | Hermes | Eagle | Courageous class | Ark Royal (1936) | Illustrious class | Implacable class | Colossus class | Majestic class | Centaur class | Unicorn | Audacity | Archer | Avenger class | Attacker class | HMS Activity | HMS Pretoria Castle | Ameer class | Merchant Aircraft Carriers | Vindex class

HMS Unicorn is a relatively foggy British carrier of #WW2, perhaps because her initial dual role as aircraft repair ship/light aircraft carrier. In a sense she is the embodiment of the limitations of British armoured carrier doctrine during the war by showcasing their limitations and acknowledging that fleet carrier needed to be more autonomous for extended operations. Started in 1939, she was completed only in March 1943 due to delays and priorites, and immediately went into action at Salerno in September 1943, followed by the Eastern Fleet and ending with the British Pacific Fleet. She she notably took part in Operation Iceberg, the campaign of Okinawa and was still used in the Korean war, ultimately sold in 1959. #royalnavy #aircraftcarrier #hmsunicorn #britishpacificfleet

Genesis and Design of the repair carrier (1936-39)

HMS Unicorn was designed at first as a repair ship and light aircraft carrier, a role split between peacetime and wartime duties. In fact her design went back to the design of the Illustrious class, first British armoured carriers. The latter had a fairly limited air group due to their small hangars and space lacked for effective repair. As said by Brown, D. K. Nelson in Vanguard: “Repair and even the major maintenance work could not be carried out in the hangars of an operational carrier without interfering with flying and hence it was decided to build a maintenance ship.”

The reduced operational endurance of the armoured carriers was both the result of treaty limitations and smaller air group, but the British Empire network of naval bases was thought to provide both facilities and support. However the Abyssinian crisis of 1935-36 which inspired their design shown also what was needed for sustained operations and it exemplified that these carriers in case of quick deployment between theaters would be soon left their land-based support behind, with the added risk of land facilities falling into enemy hands, as shown by the rapid Japanese advances later in the Pacific.

This a committee was setup in 1936 to evaluate this issue and look at possible fleet support facilities. The need of repair, maintenance and depot ships to be moored in anchorages near the action and not part in the fleet, itself at danger on the first line. The FAA during the Abyssinian crisis showed also her forward deployment followed amonth of intensive flying result in an attrition rate up to 20%, and so that replacement would be needed to compensate close to the action. Not only 20% would be missing but with the ongoing avation, an average of 10% would be in need of repair and maintenance all the time. This combine would result in an effective air group reduced by 30%, on an already limited base.

In 1937 the need for a mobile aircraft depot ship or maintenance carrier was identified whereas the new projected armoured carriers were still in design phase. But this new carrier needed much time and debates to end with a suitable ship. The committee would only snd its report in 1939. It was soon identified this new depot carrier was expected to carry 33 aircraft, made readily available for support and resupply. In 1938 as the design was precised, the design team ended with a calculated displacement of 14,750 ton (20,300 full load) and a speed of 24kts, clearly not sufficient for fleet operations, but they were supposed to operate from afar anyway. It would also need to ensire its own defence.
The tactical plan was any of these new support carriers was to support three fleet carriers, and the planned six not even included the Ark Royal, Courageous and Glorious, made for three ships of the same class being built.

It’s Controller Admiral Sir Reginald Henderson, already behind the armoured carrier design which still wanted the new carrier to retain all the features of an operational aircraft carrier, as a “spare” spare deck and act in crisis as a supplementary light aircraft carrier. in times of crisis would be invaluable. The future HMS Unicorn was to be given arresting wires, catapult and well protected munitions stores as well as a fully fonctional armoured flight deck and lifts for standard operations. Engineers however had to tone down some protection aspects, but she was still an armoured carriers by international standards, albeit lightly (see later). The design was approved in mid-1939 (date in research).

Hull and general design

For most authors and even commentators of the time in 1943, she looked like a “small ark royal”, more stubby-looking, sharing many caracteristics like the twin hangar, one usable for repair and the other for a protected park. The bow lines were modelled after Ark Royal in 1939, the most recent carrier in completion by then, and the flight deck had its edges sloping inwards a little over the prominently plated prow. Her flight deck was also “clean”. However as an auxiliary no much care was given to her aerodynamics, notably the airflow from the bow and around the island. As expecience showed, they would have an inpact on landing approach. Pilots would experience a “sudden drop” with harder landings than on other carriers. This was even aggravated by her shorter deck.

As for her hull, HMS Unicorn measured 640 ft (195.1 m) long overall at the flight deck level, 90 ft 3 in (27.51 m) wide also at flight deck level and 23 ft (7.0 m) deeply loaded. Fpor a displacement of 16,510 long tons (16,770 t) standard and 20,300 long tons (20,600 t) deeply load. This was far more than her intended 14,750 long tons (14,990 t), but additional equipments more in line to fleet carriers operations were added once the treaties were torn down during completion.


HMS Unicorn was eventually laid down at Harland & Wolff on 26 June 1939, launched in 20 November 1941 and completed on 12 March 1943 at a cost of £2,531,000. By that time not only her design was already obsolete, but her intended role became a straight use as a front line carrier. At the origin this was a project of the Admiralty motivated by reports from the Abyssinia Crisis of 1934–35 which showed an airplane specialized depot ship could be quite useful in operations. Design-wise, she was the pet project of Admiral Reginald Henderson, Controller of the Navy.

She was defined by him as to “carry out the full range of aircraft maintenance and repair work in addition to the ability to operate aircraft from the flight deck”. Later the concept was seen sound enough to convert two other fleet carriers into the same lines, the HMS persus and Pioneer. She was however somewhat overweight as completed, and stabilization was worked out. She was equipped with a 600 ft/180 m long flight deck with arresting gear a 14,000 ib (6,400 kg) strong catapult. She had two lifts and two hangars like the Ark Royal, of unequal length: Each was 16′ 6” (5.03 m) tall, and the upper one was 324 x 65ft (98 x 19.5m), the lower one 360 x 62ft (190 x 19m). Her petrol capacity was a generous 36,500 imperial gallons and she was equipped with a self-propelled lighter under the rear of the flight deck to recover and transfer disabled aircraft.” (old archive)

Armour protection layout

HMS Unicorn was indeed armoured, but at a level ideal for a ship not intended to be frontline. It was closer to HMS Atk Royal levels of protection, meaning relatively light: She had a 2 in (51 mm) armored flight deck, offering little protection against armor-piercing bombs, but her magazines were boxed and well deep inside the hull, protected by 2–3 in (51–76 mm) or armour. For ASW protection her longitudinal Bulkheads and thise protecting the hangar reached 1.5 in (38 mm). To compare, an Illustrious-class was protected overall by 4.5 in (114 mm). So she better earned the title of “protected carrier”, not better than an Essex-class. Additionally, her hangars could be divided into sections with fireproof curtains and there were fire stations and sprinkers.


Her powerplant was in now way innovative, but compact, with two shafts 15-foot (4.6 m) propellers connected to two Parsons Geares steam turbines, fed in turn by four Admiralty 3-drum boilers working at a pressure of 400 psi (2,758 kPa; 28 kgf/cm2). This enabled a total output of 40,000 shp (30,000 kW), and in turn she as capable of a top speed of 24 knots (44 km/h; 28 mph), not ideal for fleet operation, but well enough to outpace any submarine and for convoy operation (depots ships of the supply train). The weight/power ratio on this output made her relatively slow but the critical factor was range, with a 7,000 nautical mile radius at an honorable 13.5 kts based on a supply of 3,000 long tons (3,000 t) of fuel oil.


Her main armament replaced the cumbersome 4-in twin turrets of her larger fleet sisters for four twin mounts 45-calibre QF 4 in Mk XVI (102 mm) dual purpose guns, much more compact and simply shielded in positions sponsoned along the hull fore and aft, two on each broadside. They sat too low to ensire cross fire above the flight deck however.
-HMS Unicorn was designed to be fitted with four quadruple 40 mm (1.6 in) QF 2-pounder Mk VIII gun “pom-pom” AA guns. They were located fore and aft at the foot of the port island, and two more in sponsons starboard.
-She also carried four 20 mm Oerlikon guns. They were located mostly on outer small individual sponsons along both sides. This was augmented in 1944-45, although detail is not known.


The DP and AA mounts served by two HACS (High Angle Control System) directors coupled with a Type 285 gunnery radar. HMS Unicorn was the first RN ship fitted with the Type 281B early-warning radar.


Arresting cables

HMS Unicorn looked “stubby” due to her two 16ft 6in hangars sandwiched like HMS Ark Royal on a shortened 640ft length. In total she only had a 600-foot (180 m) long flight deck, 90ft wide flight deck, with arresting gears, ten cables aft of the second lift, and others between this and the fore lift (They could trap 20,000 lbs at 60 knots), plus two stopping nets (crash barriers) short of the catapult, with the same stopping power, but with a much shorter “pull-out”.


The latter catapult was located port of the centerline, and was capable of launching a 14,000-pound (6,400 kg) aircraft to 66 knots (122 km/h; 76 mph) with the tail-down launch method. This was called officially a BHIII hydraulic accelerator, same as fitted to armoured carriers.


The two hangars making her looks like a “Midget Ark Royal”, measured each 16 feet 6 inches (5.03 m) high. But they diverged in overall surface: The upper hangar reached 324ft by 65ft, the lower one 360ft by 62ft. Total surface was 40,000sq ft, almost the same amount as HMS Idomitable. There was openings to the hangars from the stern enabling her also service floatplanes. Total capacity exceeded her nominal air group: The Hangar space was sufficient to contain 48 aircraft, wings folded, with eight more, wings spread in maintenance. So a grand total of 66, not bad for a ship less than 195 m (640 ft) long, cruiser size. The idea behind the two hangar system was that reserve aircraft were to be stowed into the lower hangar, the upper one used for urgent maintenance and repair.


Aircraft were carried between them and the flight deck by two aircraft lifts or elevators located on the starboard side, of different size for different aircraft. They were not far from the island, leaving most of the port side of the deck unincumbered. The forward lift measured 33 by 45 feet (10.1 m × 13.7 m) for potential not-folding models, and the rear lift 24 by 46 feet (7.3 m × 14.0 m) only, better fit for planes having folded wings. Both were designed to lift loads of up to 20,000 lbs with a cycle time of 46 seconds. For her 36 operational aircraft she carried aviation gasoline up to 36,500 imperial gallons (166,000 l; 43,800 US gal) in buried-deep fuel tanks, unprotected. During wartime, between her regular operation crew as a ship, her full air group’s pilots, and all the technical team to repair and maintain a far larger air park, amounted to 1,200 personal in wartime.

Other facilities

She carried about six service boats in recesses into the hull, under davits, but also a self-propelled lighter stowed under the rear of the flight deck, which allowed allow unflyable aircraft to be transferred between ships or to shore facilities, and htne lifted aboard using cranes. This lighter was placed levelled at the upper hangar deck to allow aircraft to be quickly rolled onto it, on one lifted up from the water into it. Thus system was unique to this aircraft carrier and proper to her role.
With hangars intended wide and high enough to include all FAA present and future aiecraft, wings spread or folded, she could maintain any air group models, including US ones.
Both hangar decks were fitted with a network of rails and hoists to allow heavy payloads such as aircraft engines to be moved around and hauled out between aircraft or transferred in and out of the dedicated workshop, which included a very large set of spare parts, tooling, and even a working bench for engine trials.

The large engine repair shop with its test compartment were located near the bow, under the flight deck. It comprised also two large, rectangular openings for engines to be run at full power with the external airflow venting fumes out. More specialized workshops were built-in, to service the airframe, or radio equipmant as well as the electrical networtk, even woodworking or fabric repairs, against with spares and tooling machinery. At design phase already it was planed six days for an average repair with 3×6 personal work teams in rotating shifts.
Artificers and mechanics were mustered into two Special Repair Parties with full British and USN standard toolkits.
In 1944 her hangars and workshops were modified, reorganized to accept US-built aircraft, with even specialised workshops for US engines and stores for Grumman, Vought and Curtiss parts.
So that as part of the BPF she was fully capable of servicing/maintaining not only FAA Seafires, Fireflies and Barracudas but also Corsairs, Hellcats and Avengers, including those of the USN if needed. After all, she was very unique among the allies in the Pacific. The US Navy had no such ship. Due to her deck she could receive and sent back aircraft in a shorter span than regular maintenance/repair including depot with a lighter, transfer to shore facility or repair ship and return via the same mode.

A problematic island

Her only backdrop as a regular carrier for standard flying operation was her tall and bulky ship’s bridge, the highest in the RN as it sat 95ft above the wavetops. Wind flow was disturbed quite a lot and pilots were not at ease when landing on her. This island was modelled both after the on Ark Royal but also the Illustrious class. It was crowned by a main fire control top, and a tripod mast supporting radar aft of it. So she at least fill her role, with two bridges, one for carrier operation and another for ship’s manoeuvers.

Air Group

Supermarine Seafire Mk.IIb aboard HMS Unicorn, Salerno Landings 1944

Corsair Mark II aboard Unicorn, 757 Naval Air Squadron FAA, BPF July 1944

HMS Unicorn could carry and operate 33-35 aircraft all contained by the hangars in maximal capacity. However as practice changed, especially in the Pacific with the BPF, following USN standard, she was setup to have a permament deck park and had in the end twice (66-70) aircraft crowded on her flight deck crowded as a “taxi”. This air group varied in time, but it seems the kept a permament park of Seafires and Swordfishes throughout 1943-44. In a strict ferrying capacity, an average of 50 to 80 aircraft depending on the type were carried.

But when operational as fleet carrier like at Salerno and Norway, she could support 35 aicraft, comprising notably 20 non-folding Seafire IICs. But she was proven capable to ferry also 69 folding-wings Seafire IIIs. This became even her most common payload as the Seafire, a dream to fly and formidable fighter, was never intended for carrier use originally and was prone to break its landing gear or damage her structure at each landing. Wilcats and Corsairs were infinitely more robust. So she was a frequent “guest” aboard Unicorn in 1944-45. Given her capacity she was paradoxically not able to repair that much aicraft: She could have about 24 aircraft under repair at any one time, supposedly wings spread.

According to various lists, this included the Fairey Fulmar, Seafire, Martlet (Wildcat), Corsair, Swordfish, Albacore, Barracuda, Walrus (seaplane) and Tarpon (Avenger). However these were mostly repaired models, and the “home list”, those for sure par tof her permament park could be listed below:
-In May 1943 as completed: 18 Swordfish, rest unknown
-July 1943: 10 Seafire, 13 Swordfish
-September 1943: 17 Wildcat, 38 Seafire and 3 Swordfish
-1944: Photo shows seafires and Barracudas, Walrus…
-1945: Likely resident Corsairs, Wildcats and Seafires

General Assessment

The funny part of the ship when approved before the war was taht on plans she (HMS Unicorn) was in many respects indistinguishable from an active fleet carrier and already back then US filled its authorized tonnage, and when completed in 1943, it was seen as supplementary to prewar approved combat-capable carriers.

So some in the admiralty worked out between treaty lines and the Naval Law Department to recommend HMS Unicorn to be classified as an auxiliary, according to her primary role to support carriers liked armed tenders for submarine or destroyer flotillas. Her aircraft carrier appearance was “sold” as a necessary adaptation to her trade, and even looked at destroyer tenders had the time which indeed looked large very large, stretched destroyer in silhouette. But in the end only one was ordered by fear for suspicion in 1939, not the three planned for all active carriers. Emergency war program in any case had it all reset anyway and auxiliaries were out of the question now.

Shifts in priorities during construction would not only affect Unicorn but also Implacable and Indefatigable, completed way after the Illustrious class, despite started and planned as part of the same bunch.

In service HMS Unicorn was recoignised as indeed slow, but this in not way plagued her utility. She was found quite adequate for regular carrier operation in settled fronts like landing areas, starting with Salerno. Sehe only started to play her intended role in the Pacific and played it wall. In fact her general flexibility made her in a sense, the precursor to modern SVTOL/Helicopter assault ships. Indeed, one often overlooked aspect was her floating hospital facilitiesn reminiscent of these modern assault ships. There was a large sick bay and fully equipped surgery and even dental rooms, twin medical stations for grave, urgent injuries in addition to the hospital facility. In short she could “treat” far more than her crew, but other fleet carriers injured men as well, possibly flew from modified flying ambulances, but it’s a topic worth researching.

Old author’s illustration

⚙ specifications

Displacement 13,310 t. standard – 24,000 t. Fully loaded
Dimensions 640 ft x 90 ft 3 in x 23 ft (195 x 27,5 x 7m)
Propulsion 2 shaft Parsons geared turbines, 4 Admiralty WT boilers, 40,000 sh
Speed Top speed 24 knots
Range Oil: 3,157 t- 7,000 nm/18 knots or 11,000 nm/13.5 kts
Armament 4×2 4 in MK IVI, 4×4 40 mm Bofors AA, 12x20mm Oerlikon AA, 33 planes
Protection Flight Deck 51mm, Bulkheads 36-38mm, Boxed Magazines 51-76mm
Crew 1200 with air crew

Read More


Accinelli, Robert (23 January 1996). Crisis and Commitment: United States Policy toward Taiwan, 1950-1955.
Brown, D. K. (1984). “HMS Unicorn: The Development of a Design 1937–39”. Warship VIII. Conway
Blackman, Raymond V. B. (ed.). Jane’s Fighting Ships 1953–54. McGraw-Hill Book Company.
Brown, J. D. (2009). Carrier Operations in World War II. NIP
Chesneau, Roger, ed. (1980). Conway’s All the World’s Fighting Ships 1922–1946.
Campbell, John (1985). Naval Weapons of World War II. NIP
Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). Chatham Publishing.
Ford, Roger; Gibbons, Tony; Hewson, Rob; Jackson, Bob; Ross, David (2001). The Encyclopedia of Ships. Amber Books.
Friedman, Norman (1988). British Carrier Aviation: The Evolution of the Ships and Their Aircraft. NIP
Garver, John W. (30 April 1997). The Sino-American Alliance, Nationalist China and American Cold war Strategy in Asia.
Hobbs, David (2007). Moving Bases: Royal Navy Maintenance Carriers and MONABs. Maritime Books.
Hobbs, David (2011). The British Pacific Fleet: The Royal Navy’s Most Powerful Strike Force. NIP
Howse, Derek (1993). Radar at Sea: The Royal Navy in World War 2. NIP
Lenton, H. T. (1998). British & Commonwealth Warships of the Second World War. NIP
McCluskie, Tom (2013). The Rise and Fall of Harland and Wolff. Stroud: The History Press.
Sturtivant, Ray (1984). The Squadrons of the Fleet Air Arm. Tonbridge, UK: Air-Britain (Historians).


On armouredcarriers.com
On navypedia.org/
telegraph.co.uk/news On /Captain-George-Baldwin
On maritimequest.com/
On britains-smallwars.com/
CC photos

Model Kits

The only one known: HP-Models No. WWII-WL-GB-172 1:700, a rather old kit. Photos. It seems also that White Ensign models made it too, no longer, neither in stock.


HMS Unicorn in service

HMS Unicorn was completed after many delays on 12 March 1943, and to accelerate the process, the Admiralty decided in 1942 that she would not be equipped with her full maintenance and repair equipment suite. Total cost without armaments, sensors and air group amounted to £2,531,000. She started working up after sea trials, and saw 818 and 824 Squadrons arriving, landing aboard in April 1943. 818 Squadron comprised nine Fairey Swordfish torpedo bombers while 824 Squadron comprised six of them.

European waters: Norway, Mediterranean

Underway in the Atlantic, 1943

887 Squadron arrived just afterwards, with nine of the brand new Supermarine Seafire IIC fighter. They all made their carrier qualification in home waters. By late May 1943, HMS Unicorn departed for her first escort mission, with Convoy MKF 15 to Gibraltar taxiing Royal Air Force Bristol Beaufighters. She escorted the returning convoy to the Clyde estuary by early June. With HMS Illustrious, she was sent to operate along the Norwegian coast (Operation Governor) which was a diversion for the Allied landings in Sicily, by early July. She carried 887 Squadron instead of 800 Squadron, equipped with Hawker Sea Hurricanes, hoping to inflict a lot of damage on the Luftwaffe based in Norway.

Atlantic 1943, underway – IWM

HMS Unicorn newt was reassigned to Force V comprising several British carriers under overall command of Admiral Philip Vian. This was the air cover of Operation Avalanche, the Allied landings at Salerno, and first big operation of HMS Unicorn as a fleet carrier. In preparation she had her two Swordfish squadrons landed only keeping a small detachment of three 818 models for abtntiship self-defence, the rest being composed of the Sea Hurricanes of 800 Squadron, soon replaced by Seafires of 809 and 897 Squadrons (10 aircraft each) making for a total of 33 planes overall. HMS Unicorn joined Force V in August 1943 at Gibraltar and sailed for the Central Mediterranean for intensive training before the operation commebced on 9 September.

Her Seafires flew 75 sorties the first day, 60 on 10 September, but attrition in carrier landings in low wind conditions made her suffer even worse than any other fleet carrier due to the disturbances caused by her large island. She had the highest ratio of landing accidents in the fleet. 44 sorties only were flown on 11 September, 18-12 September, mechanics repairing ten Seafires during the night.
Fighter shortage became such an issue than those of Illustrious and Formidable intended to cover and air strike on the incoming Regia Marina poised to to interfere with the invasion, were instead reassigned as air cover over the landings area. On 12 September, 887 Squadron was back at half-strenght, at least providing a CAP of six Seafires, soon moved to a temporary airfield ashore, ensuring better landings.
After the operation was concluded, HMS Unicorn went back home on 20 September with a large load of damaged Seafires, her own and those of the fleet carriers, as intended when she was first designed. These were off-loaded at Glasgow for repairs. HMS Unicorn had her first refit in her original builder Yard, Harland and Wolff of Belfast, and she was reconfigured for her designed role as aircraft repair ship, with her original full repair suite, workshops, parts magazines and all, left over when she was first completed.
So Salerno would be her only true “fleet carrier” operation, but the Seafire proved at this stage not reliable for prolongated use, and the Martlet and Sea Hurricane were now obsolete.

Indian Ocean

HMS Unicorn (camouflaged, in the background) and illustrious at Trincomanlee, Ceylon, 1944. Notice the difference in height of the former

Servicing a Supermarine Walrus used for reconnaissance with her crew, far east 1944

By the end of December 1943, HMS Unicorn joined HMS Illustrious, escorted by the battlecruiser HMS Renown and Queen Elizabeth, Valiant, en route to bolster the Eastern Fleet. She only carried her permament self-defence four Swordfish from 818 Squadron at the time.
Indeed she acted as taxi for the Royal Navy Air Station at Cochin in India. She arrived and flew out her plans there on 27 January 1944. Next, she headed to Trincomalee, Ceylon, arriving on 2 February. She was immediately tasked to repair aicraft and her deck was used for landing practice. She had a brief refit in Bombay in May 1944. On 23 August, 818 Squadron was transferred to Atheling (and disbanded soon after). On 7 November, 817 Squadron flew aboard, counting Fairey Barracudas equipped with ASW warfare. At the time indeed, HMS Unicorn was assigned to the convoy patrol route of the cape, she was to be based in Durban, South Africa. She was modified there with separate workshops and equipment to service American engines, not to the same standard, in order to return to the pacific and be of some use for the now largely provided US fighters, the robusts Hellcats and Corsairs.

When done at the end of August, HMS Unicorn was officially transferred to the newly formed British Pacific Fleet (BPF). She left Durban on 1 January 1945 for Colombo in Ceylon, retruning to her deck-landing practice for BPF pilots, ahd repairing damaged planes during these training sessions. She next loaded 82 aircraft and 120 engines to be landed in Australia, which were all the available stocks of the Eastern Fleet, not rebaptised and relocated to the Pacific. Departing for Sydney on 29 January she arrived on 12 February.


With the BPF (she is second from the foreground) at anchor in 1945, Manus Island
HMS Unicorn sailed in 28 February for Manus Island (Admiralty Islands) to provide again BPF training and repair services. The BPF was prepared for Operation Iceberg. Next she was moved to San Pedro Bay, Philippines, arriving on 27 March. She served as intermediate replenishment base, and was prepared to move for Operation Iceberg proper. Recuperating her fleet carrier role, she was assigned the attack of attack Japanese airfields in the Sakishima Islands and Formosa in the early part of the invasion of Okinawa.

Operation Iceberg
HMS Unicorn was moslty use to prepare aircraft for operational squadrons, then flew aboard fleet carriers for first line operation. It was mostly preparation and maintenance but she still performed repairs and modification of 105 aircraft by March–May 1945. She returned to Australia on 22 May to take aboard parts and engines, arriving in Sydney on 1 June. She moved to Brisbane on 6 June and entered the Cairncross Dockyard to have her bottom scrapped in drydock, and afterwards loaded more replacement aircraft.

Back to Manus on 22 July, HMS Unicorn prepared operations off Japan. July-August saw her rarely theatened by Kamikaze as she never was frontline and she soldiered on until the Emperor declared the capitulation on 15 August. Her next task was to ferry aircraft and equipment, but also men to Australia, arriving at Sydney on 6 November. By December she sailed for home. She arrived in Plymouth by January 1946 to decommissioned, placed in reserve. This made for a fairly short service by then of just three years, so the RN looked at ways to use her in the future.

Post-War Career

In 1949 the far east proved a powdercake and HMS Unicorn was reactivated for service, and support of the carrier HMS Triumph (Colossus class). She sailed from Devonport on 22 September loaded to the brim with spare Seafires and Fireflies.

As the Korean War started by June 1950, she disembarked her air group, equipment and maintenance personnel to RAF Sembawang in Singapore. She was reassigned as a replenishment carrier to the Royal Navy and Commonwealth naval air forces deployed on the theater. HMS Unicorn left Singapore on 11 July for Sasebo in Japan (20 July) sending 7 Seafires and 5 Fireflies to HMS Triumph. By August she carried the 1st Battalion, Middlesex Regiment and 27th Brigade HQ from Hong Kong to Pusan on 29 August. She also unloaded next more supplies in Sasebo and was sent back to Singapore for a refit.

Back in December 1950 she carried 400 troops and an air park, supplies and equipment. Like in the old days, mostly green pilots practice deck-landing en route. By March, she ferried Gloster Meteor jets (No. 77 Squadron RAAF) to Iwakuni in Japan. She spent the next three months there as an accommodation ship. In June 1951, she was back as a ferry carrier. However while corssing the Shimonoseki Strait on 2 October her Island cut overhead power cables between Honshu and Kyushu after a heavy snowfall.

On 21 November she exchanged crews with the carrier HMS Warrior at Singapore so to be free for a refit, completed on 20 January 1952. She was back to ferry duties. In July 1952 she was used as a spare flight deck for damaged aircraft from fleet carriers, in order not to disrupt strike operations.
On 27 July she entered Singapore load replacement aircraft. This included more jet-powered Meteors. On 9 August she headed for Japan and by September, the received her first CAP since a very long time: HMS Ocean’s four Hawker Sea Fury fighters for air cover during strike operations. Again, this freed Ocean to concentrate on strikes only.
HMS Unicorn received a drydoch maintenance in October 1952. She embarked the First Sea Lord, Admiral Rhoderick McGrigor and CiC, Far East Station to tour Commonwealth forces based in Japan. At least she saw some action, striking North Korean coastwatchers at Chopekki Point. This was her only wartime active strike.

With the BPF in Sasebo, Japan, 1950

Back to Singapore for a new refit on 15 December 1952, she as inactivated until17 July 1953 and on the 26th while en route for Japan she received an SOS from SS Inchkilda, atacked by pirates south of the Wuqiu region (Taiwan Strait), which proved to be gunboats of the ROC Anti-Communist National Salvation Army (ACNSA). She arrived at high speed and seeing her, pirates abandoned their prize. She went close to the freighter with all guns bearing and fired a warning volley for good effect. The Korean Armistice was learned the following day. Still, she became the sailor of HMS Ocean on two more patrols on 30 July and 25–29 August, monitoring North Korean compliance with the terms. On 15 October she departed for home, ending her last combat deplmoyment. She arrived at Devonport on 17 November.

With sea Fury aboard, Kure 1950 src FLICKR

Unicorn In Singapore, 1953, FLICKR via pinterest

Fom destinationjourneys.com via pintesrest

Hawker Sea fury taking off, 1950s – IWM


Well before that, in 1951, the admiralty already had some ideas about her possible conversion. In 1951, indeed was planned a modernisation to accept modern and heavier jet aircraft. She was to be fitted with a new steam catapult, reinforced flight deck and lifts, the forward one being enlarged. She was to be also fitted with a new crane and new lighter aft. The Director of Naval Construction (DNC) proposed to combine both hangars into a single one due to the height of the new models, but this proposal was rejected based on budget. HMS Unicorn was to be taken out from the reserve in July 1954 for such conversion, but it was cancelled well before in November 1952. Indeed, some light fleet carriers of the Colossus/Majestic class were converted while under completion as repair ships already. The admiralty also considered having a budget to refit existing carriers with angled flight decksmight have all budgetary priority.
Thus, a new project was born, to convert as a Ferry Carrier in June 1953. This was done quickly but she returned in extended reserve in March 1957, then stricken in 1958 and ultimately sold for scrap in June 1959. She was broken up at Dalmuir, arriving on 15 June and the process ended at Troon in 1960.

Type XB U-Boats (1941)

The Type X (XB) U-boats were a special type of German submarines of WW2 originally designed as long-range minelayers, but later used as long-range cargo transports as the Type IXD U-Boats, Italian Romolo-class submarines and several Japanese Types. In all, only eight were built, consistent for this complex and costly type compared to other nations. Six on the eight boats, the largest U-Boats of WW2, were lost: U-116 in October 1942, North Atlantic, U-117 in August 1943 by USS Card, U-118 on 12 June 1943 by USS Bogue, U-119 on 24 June 1943 by HMS Starling, U-220 on 28 October 1943 by USS Block Island and U-233 on 5 July 1944 by USS Baker and USS Thomas.

Design Development


Previous German experience

Minelayer submarines seemed very seducive to many admiralties before even WWI, when this new boat was barely taken seriously as a weapon, still. The Germans developed at first two classes, the ten U71 class (1915), which carried thirty-four 100cm (3.2ft or 39 in) mines in horizontal stern tubes, and the eight U117 (1917) which carried 42 in tubes and 30 on deck stowage. Later an entire line of specialized coastal minelayers, called the UC types: UC1 (launched 1915), UC16 (launched 1916-18), UC80 (1918, most never completed).

Moderate International Adoption

Many were passed on the entent powers as war reparation in 1919-1920 and tested. Soon, several were built, and the allies had at least an operational class when WW2 broke out, such as the British Grampus class and the French Saphir class, the US had the single USS Argonaut (1927), the IJN developed the KRS class in 1926, Italy operated the Bragadin class (1929) and Pietro Micca (1935) and the Soviet Union the series XI, XIII/XIIIbis and XIV. These were not very common types overall compared to standard coastal and oceanic types.

German Reboot: The Batiray

During the interwar the German Navy was forbidden by the Versailles treaty to have any submarines. The development of a design office in the Netherlands, Ingenieurskantoor voor Scheepsbouw to keep the skills sharp in the 1920s helped at least to continue working on improved types, but based always on foreign orders and specifications. There was no minelayer type until the Turkish Batiray (1938), a 1044 tons (surfaced) type capable of carrying 40 mines, built at Germaniawerft and launched in August 1939, but taken over by the German Navy after completion. She made her sea trials under her original Trurkish name, but was thus never delivered to Turkey and instead renamed UA, kept for experimentations with the type.

But as the war broke out she was quickly operational, counting on her six torpedo tubes and long range. Under command of Kapitänleutnant Hans COHAUSZ, U-A made two sorties from Sept 17, 1939 to Oct 31, 1940, with 92 days at sea for 7 victories. By late 1940 to early 1941 she conducted an attack on convoy OB 293. We are not going to dive deep into her career, but in between standard patrols she also was used as a cargo, and ended scuttled in Kiel in May 1945. No doubt that her design could be considered as a prototype for the Type X class, although in between the ordnance came with a new type of mine and specifications changed. She will be covered in her own post soon.

Early specifications and development of the Type X (XA)

The Type X was originally designed specifically to accommodate the newly developed Schachtmine A (SMA) moored mine. The initial specification asked to provide dry storage for these mines, which needed their detonators to be individually adjusted before launch by the crew. This designed was established in the design bureau of the Marinewerftabteilung, in coordination with the Marinewaffenamt (MWa) for the mines and their tubes, and the Marinekonstruktionsamt (K) which setup the requirements.
The final submarine was projected to have a 2,500 tonnes displacement, surfaced. As work progressed, it was envisioned a further variant, the Type XA which was to be fitted with extra mine shafts in the saddle tanks, but they were never ordered as war priority changed.

Comparison between the Type XB and Type IX variants

XB U-Boats were experimental submarines developed before the war were larger and more powerful than other U-Boats to enable long distance operations, and remaining submerged for extended periods of time thanks to a large battery capacity. Thus, they were in theory able to mine the Canadian and US east coast among others. However as priorities shifted, they were soon swapped from roles, as supply vessels for German submarines operating in the Atlantic Ocean with fuel, torpedoes, and other essential supplies as the Type XIV, or more commonly to transport valuable assets to distant ports, like Japan.
The final design settled on the XB type, which was around 200 feet (60 meters) long and had a displacement of 1,600 tons when surfaced, and 2,000 tons when submerged. They were powered by diesel-electric engines and had a top speed of around 16 knots when surfaced and 9 knots when submerged. The crew complement was around 50 men.


Surrendered U-Boats in portsmouth, 1945
A total of eight Type XB boats were produced, which replaced the initial mine chamber of the previous Type XA with six vertical wet storage shafts in the forward section of the hull. They were all built at F. Krupp Germaniawerft, Kiel, in three batches from 1941 to 1944:

Design of the class

Hull and general design

(plans are in search mode).
The U-Boat 1,763 tonnes (1,735 long tons) surfaced, 2,177 tonnes (2,143 long tons) submerged. They were the longest of all active U-Boats of the Kriegsmarine, at 89.80 m (294 ft 7 in) o/a long, for 70.90 m (232 ft 7 in) for the pressure hull with a beam of 9.20 m (30 ft 2 in) o/a. The internal pressure hull had a diameter of 4.75 m (15 ft 7 in) pressure hull. The type was 10.20 m (33 ft 6 in) tall up to the conning tower’s top, periscopes down in their wells. The Draught was 4.71 m (15 ft 5 in), which gave them an elongated silhouette, especially compared to the Type XIV. The crew comprised 5 officers, and 47 enlisted sailors. Compartimentation was the same as the Type XI with the exception of a forward compartment without torpedo tube chamber and instead a serie of axial mine wells. The mine wells were many. The taller axial six vertical wells forward carried three each, for 18 mines, added the the with additional 48 mines in 12 shafts (2 each) set into the saddle tanks, either side, for a grand total of thirty mine wells, carrying overall 66 mines.
The tradeoff was the elimination of froward torpedo tubes and keeping only two stern torpedo tubes for defence. When used as cargoes drum-like freight containers had been created for this class, so they they could be carried in the 30 mine shafts, or had these freight containers welded on top of the lateral shafts, making the conversion final.


The powerplant comprised two supercharged Germaniawerft F46 A9, 9-cylinder, four-stroke diesel engines, 4,800 PS (4,700 bhp; 3,500 kW) for surface running. This was completed by two AEG GU 720/8-287 electric motors for underwater running, the latter rated for 1,100 PS (1,100 shp; 810 kW). Top speed surfaced was ranging between 16.4 and 17 knots surfaced, for 7 knots underwater, which was “in the norm” at the time. They did not have to charge through convoys at night. Of course these performances degraded when used as cargoes, with well stuffed payload drums (like gasoline)…
Images and full doc (in spanish) – Start and sound video

Range: 18,450 nautical miles (34,170 km; 21,230 mi) at 10 knots (19 km/h; 12 mph) surfaced and 93 nmi (172 km; 107 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged. They carried 338 tons of diesel oil.
Test depth was calculated at a crush depth at 220 m (720 ft). Safety operational depht was 100 mm (330 ft). But robust construction meant they could in theory dive probably down to 230 m in extreme urge. At 2,710 tonnes submerged, fully loaded, they were the largest German U-boats ever built, but translated into poor agility and long diving time.


It varied by boat and over time: The first boats were delivered with a single 105/42 SK C/32 aft deck gun, one 37mm/80 SK C/30 and one 20/65 C/38 on both CT platforms, and the two aft 533 TT stern and 66 mines. U233 and 234 had the deck gun removed and instead had a 37mm/69 FlaK M/42, and two twin 20mm/65 C/38 AA guns, and same.

Torpedo Tubes

The two stern 53.3 cm (21 in) torpedo tubes had 15 torpedoes in reserve. The torpedoes fired, by default of a better information, are assumed to the the standard G7A.
Weight 1538 kg, 280 kg warhead, 300 g Pentrite detonator, can impact to 16 degrees. Top speed 30/40/44 knots settings at 1–12 to 1–15 m underwater and respective range of 12000/7500/5000m. Powered by a 4-cylinder steam engine running on Decaline (110/350 Hp depenbding of the setting) and 1170/1280/ rpm. Using a contrarotative (six-blades total) propeller.

Deck Gun

Initial boats had a single 10.5 cm (4.1 in) deck gun (200 rounds) located aft of the conning tower. This standard gun was developed from 1941 and soon became the standard German U-boat deck gun throughout the war. It fired a fixed 15.1 kilograms (33 lb) HE round with an elevation for the LC/32 mount of -10 to +35. Muzzle velocity was 785 m/s (2,580 ft/s) and max range 15 kilometers but rather 10 km useful (11,000 yd).


37mm/39 FLAK M/42, U-Boat mount type.
37mm/80 SK C/30: Single-shot semi-automatic breech, vertical sliding-block 30 rpm mv 1,000 m/s (3,300 ft/s) range 2,000 m (6,600 ft)/8,500 m (9,300 yd) 37.5°
37mm/39 FLAK M42: Recoil-operated sliding breech block 250 rpm cyclic (5-round clips) mv 865 m/s (2,840 ft/s) range 4,800 m (5,200 yd)@85°,6,400 m (7,000 yd)@45°
20mm/65 FLAK C/38: 450 rpm cyclic 180 rpm (20 rds mag.) mv 900 m/s (2,953 ft/s) 2,200 m (2,406 yds) ceiling

The surviving boats in 1944 had their conning tower to be ported on the second batch as standard: 37mm/69 FlaK M/42, and two twin 20mm/65 C/38 AA guns, on a two-staged conning tower aft platform arrangement inaugurated in 1943 by the “U-FLAK” modified Type VIIC.

37mm/80 SK C/30 on a Type IX (Bundesarchiv)

Mines: Schachtmine A (SMA) moored type

66 × SMA mines. The SMA is a moored mine similar to the TMA but with a much larger explosive charge. It was tailored to be dropped from vertical shafts, so balically for the Type XB and VIID.
Length/Diameter: 7.1ft (2.15m)/4.4ft (1.33m)
Maximum Depth set: 250m
Warhead: 350kg
Read More: 1 2 3


FUMO 30 and Seetakt systems (ONI).
As completed in 1941-1942 the Type XB carried a S-Gerät sonar and a GHG hydrophone, standard for the time. For those of the batches completed 1942-1943, they gained a FuMO 30 radar and FuMB 1 Metox ECM suite in addition. Those released in 1943-44 had the same plus a FuMB 3 Bali and FuMB 6 Palau ECM suites. In 1945 the survivors received the FuMO 61 radar in replacement for the model 30.

Original plans: Unfortunately only the forward profile survived.

Decks arrangement over view

Internals of the Type XB (src Uboat archives, see notes)

⚙ specifications

Displacement 1,763 tonnes surfaced/2,177 tonnes submerged
Dimensions 89.80 m (294 ft 7 in), 9.20 m (30 ft 2 in) wide draught 4.71 m (15 ft 5 in)
Propulsion 2× diesels, 4,700 bhp, 2× AEG electric motors 1,100 PS
Speed 17 kts/7 kts surface/sub.
Range 18,450 nautical miles (34,170 km; 21,230 mi)/10 kts
Armament 1x 10.5 cm deck gun, 2× 21 in stern TTs 15 Torps. 66 × SMA mines
Crush depht Calculated crush depth: 220 m (720 ft)
Crew 5 officers, 47 enlisted

The alternative design: Type VIID

The only other class in service with the Kriegsmarine was a modified Type VII (the great U-Boat standard), completely stretched and modified as the very center of the boat, aft of the conning tower, housed 15 SMA Mines, same type as the XB, but unlike the latter, they were housed in five wells aft of the conning tower, each tall enough to house three mines each, so fifteen in all. The rest of the submersible remained essentially a late improved Type VIIC/42.
Som thoughts were also given to port such conversion to the Type larger Type IXD, but this never was implemented.
And there was the ex-HMS Seal, captured in the Skagerrak and renamed “UB” to distinguish itself from the previous “UA” ex-Batiray.

Assessment of the XB type

U-234 torpedoed after the war by USS Greenfish. A captured, war prize, she was tested throughly before.
Six of the eight boats built were sunk during the war (four with all hands) but two survived World War II. One survivor was U-234, which surrendered to US Navy ships on 14 May 1945 while en route for Japan with a cargo that included 560 kg uranium oxide, two Me 262 jet fighters, and 10 jet engines.
The other type XB to survive was U-219 which reached Batavia (present-day Jakarta) in December 1944 with a cargo including dismantled V-2 rockets for Japan. Following Germany’s surrender, U-219 was seized by the Japanese at Batavia on 8 May 1945 and on 15 July 1945 was placed into service with the Imperial Japanese Navy as I-505.

Read More


Conway’s all the worlds fighting ships 1921-1947
Campbell, John Naval Weapons of World War Two
Williamson & Palmer 2002
Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. Vol. 2. Conway
Williamson, Gordon; Palmer, Ian (2002). Kriegsmarine U-boats 1939-45: Vol 2. Osprey Publishing


U-Boat archive, – Kriegsmarine full manual
on uboat.net
U116 on ubootarchiv.de
Type_X_submarine wiki
on forum.axishistory.com/
UA on ubootarchiv.de/
Batiray on dasboot.forumactif.com/
kbismarck.com kriegsmarine-organization

Model Kits

Neptun 1072 German Submarine U 234 Type XB 1942 1/1250 Scale Model Ship.


(no photo)
U-116 was the lead boat for the class. She was Commissioned on 26 July 1941 and after a quick workout after trials and single training cruise as part og the 2nd Uboat flotilla, she was declared ready for service and departed for her first wartime cruise.
1st patrol:
U-116 was assigned to to the 1st U-boat Flotilla on 1 February 1942. She departed Kiel on 4 April 1942 for Bergen, Norway via Heligoland. Departing Bergen on 25 April, she made the dangerous touor of British Isles before arriving at Lorient, occupied France, on 5 May. She spotted neither attack any ship.
2nd patrol U-116 sailed from Lorient on 16 May 1942 in a mid-Atlantic patrol for 25 days, and back on 9 June. No results.
3rd patrol: U-116 was ordered to the less protected coast of West Africa. She attacked Convoy OS-33 (south of the Azores) on 12 July 1942. Using the usual tactic and penetrating the convoy by night, she fired one torpedo at the 7,093 GRT merchant Cortona, damaged but not sunk. She was finished off by U-201. 9 hours after, she fired her two stern torpedoes on the 4,284 GRT British merchant Shaftesbury, sinking in 15 minutes. She was back at Lorient on 23 August (58 days cruise).
4th patrol: For her last patrol, with a new captain, Oberleutnant zur See Wilhelm Grimme she left Lorient on 22 September 1942, but was reported missing in action. Her last message was dated bacl 6 October in the North Atlantic. Her fate is unknown (likely she was sunk by escorts, but unconfirmed on the allied side), and disappeared with 56 men aboard.


U-117 under attack by US Navy aircraft in the Atlantic, 7 August 1943
U-117 was commissioned on 25 October 1941, much later than her sister U-116, and thus was only operational from mid-1942.
1st Patrol:
On 19 September 1942, she left Kiel for the North Atlantic and along the coast of Norway, then Iceland. She made the great circle back to Lorient in France via the Bay of Biscaye. U-117 she made no encounter during this patrol.
Second patrol: Apparetntly she came back from lorient to Germany (same trip at the reverse) as she departed from Königsberg on 12 October 1942 to Iceland and to the Bay of Biscay, then Lorient on 22 November 1942, mmaking no encounter.
Third patrol:
U-117’s started from Lorient on 23 December 1942, but she encountered no Allied vessels. She was back to her homeport on 3 February 1943.
Fourth patrol:
Departing Lorient on 31 March 1943 for Mid-Atlantic, she headed south to the Canary Islands and from there, French Morocco. On 11 April 1943, she laid a minefield in the usual paths of entry and exit of the Mediterranean to the Atlantic. Her minefield claimed the Matt W. Ransom (damaged). On 25 April 1943, she also claimed SS Empire Morn. The latter was so damage she was later declared a total constructive loss.
Fifth patrol:
On 1 December 1942, U-117 was reassigned to the 12th U-boat Flotilla based in Bordeaux, operating with Italian submarines. She departed Bordeaux on 22 July 1943 with the mission to lay 66 mines off New York City, the very mission they had been designed for in the first place. On 27 July, she was redirected to refuel U-66 also heading for North America. But the latter was attacked before they met by aviation on 3 August, and upon arrival, U-117 provided medical assistance on 6 August.

The attack of 8 August 1942 from USS Card. This was one of the earliest success of the Avenger’s new FIDO ASW homing torpedo.

However on the 7th, a several Grumman TBF Avengers from VC-1 USN, USS Card spotted and attacked the two U-boats caught on the surface while U-117 was refueling U-66. Depth charges fell between them, and U-117 was hit by a FIDO homing torpedo. Two more Avengers and two F4F Wildcats coming in a second wave from USS Card forced U-117 to dive and rained depth charges. She was hit by at least one FIDO homing torpedoe and sank with all hands but U-66 escaped back to Lorient.


U-118 under attack by USS Bogue’s plane in 1943
U-118 was first commissoned on 23 September 1941 (she was later repaired and recommissioned on 6 December 1941). She tained with the 2nd flotilla.

First patrol
U-118 departed Kiel on 19 September 1942 bound for the North Sea, and well-knopn “Faroe Gap” to enter the Atlantic Ocean. While south of Iceland she was spotted and attacked on 29 September but damage was moderate. She reached Lorient on 16 October and spent some time in repairs.
Second patrol
She departed Lorient to take position between the Azores and Madeira. But after a week she made no spotting and transited from Lorient to Brest on 12-13 December.
Third patrol
Departing Brest on 25 January 1943 she reached Gibraltar via the Bay of Biscaye and Spanish coast. Taking position close to the strait, she spotted and sank Baltonia, Empire Mordred and Mary Slessor on 7 February alone, and lating her minefield the 1st. It claimed Duero the 10th (damaged). The same minefield claimed HMCS Weyburn on 22 February (sunk), the first warship kill of the entire class so far. Apparently her depth charge primers detonated, blasting her and damaging a nearby destroyer coming in assistance. U-118 returned to Bordeaux on 26 February.
Fourth patrol
U-118 was attacked underway off the Canary Islands by two aircraft. Her position was signalled and soon was followed by a wave of eight planes from USS Bogue. She was strafed with .50″ and .30″ ammunition and bombed. One made a direct hit and she split in tow, exploding with oil and debris projected far away. 16 men however survived, later picked up by the escort USS Osmond Ingram.


(no pic) U-119 was commissioned on 2 April 1942. After training and workout in the Baltic she was declared ready for operation in the summer, under command of Kapitänleutnant Alois Zech on 2 April 1942, and later Horst-Tessen von Kameke from 15 April 1943. After training with the 4th U-boat Flotilla from April 1942, she really was declared only operational on 1 February 1943 and was transferred to the 12th flotilla.
After a short run from Kiel to Frederikshaven (Denmark) and back on 4 to 10 August 1942 she was declared fit for wartime action and prepared for her first patrol, from Kiel, departing on 6 February 1943 and crossing the North Sea, making the great circle off the northern coast of Iceland, down to Mid-Atlantic, the Bay of Biscay and her forward operating based at Bordeaux, arrivong on 1st April. She was unsuccessfully attacked on 29 April 1943 by a Short Sunderland (461 Squadron RAAF), having one man was killed on deck.
On 1 June she laid a minefield. On 3 June she managed to sink Halma (2,937 GRT), east of Halifax, Nova Scotia. She also damaged John A. Poor (7,176 GRT) on 27 July and both vessel hit mines but the second survived.
The end: U-119 was sunk 24 June 1943 in the Bay of Biscay, north-west of Cape Ortegal, Spain, while she was coming back from her mission to the Gironde estuary. She was spotted surfaced, then depht-charged and eventually fired on, and rammed by the British sloop HMS Starling, sinking with all hands.


(no pic) U-219 was commisioned on 12 December 1942. Training and workout went on until later the next, and she was really operational in late 1943 under command of Korvettenkapitän Walter Burghagen. She had one of the most interesting career of these boats.
First patrol:
U-219 was sent to the South Atlantic with the second “Monsun Gruppe“, navigating to the Indian Ocean, after rounding the British Isles and west of Ireland. They took the long crossing voyage via the south atlantic, West Coast of Africa and rounding the cape until eventually reaching Penang. This U-boat group was attached to 33rd U-boat Flotilla (U-848, U-849, U-850, U-177, and U-510).
U-219 was to lay mines off Cape Town and Colombo. However the group’s U-tanker was destroyed and U-219 was requested to refuel other submarines to return to Germany. U-510 however made it to Penang. U-219 arrived in France and was prepared for a transport mission, operating from Bordeaux.
Second patrol
U-219 left Bordeaux on 23 August 1944 with U-195 and U-180, all heavily loaded with two Japanese officers aboard as translators and observers, and a precious strategic cargo: Uranium oxide for the Japanese nuclear program, blueprints for advanced tech and weapons, twelve dismantled V-2 rockets (in part aboard U-195). While underway, they spent most of their time surfaced and of course were attacked in a single dau five times on 28 September by three Grumman Avengers from USS Tripoli west-southwest of Cape Verde but their FLAK combined managed to shot down one of these. This was the only serious attack of the trip, which concluded successfully when both U-Boats reached reached Japan-occupied Batavia (Jakarta) in December 1944.
In Japanese service
U-219 was prepared to sail back to Germany with some precious materials helping the German industry. However in May 1945 she still had not yet departed. With Germany’s surrender, U-219 was seized by the Japanese at Batavia, on 5 May. On 15 July after some modifications and the help of the German crew, which part remained, she became the Imperial Japanese Navy’s I-505. I-505 career was short however as she was captured at Surabaya in August 1945 by the Royal Navy. She practically had no time to make any war patrol. The British inspected her throughly and made some tests. After being mothballed for a few weeks it was decided to finish her off as a target. She was expended on 3 February 1946 by gunfire and depth charges from the Dutch destroyer HNLMS Kortenaer off the Sunda Strait.


(no pic)
First and last Patrol
U-220 was commissioned on 27 March 1943, with Oberleutnant zur See Bruno Barber in command. She start training in the 4th U-boat Flotilla and later the 12th flotilla when ready for operations.
Following her departure from Kiel, to Bergen she was patrolling on 8 September 1943 in the Faroe Gap (between Iceland and Faroe Islands) with a final destination being the North American coast. Off St. Johns, Canada, she laid 66 magnetic mines (9 October). This minefield later claimed the US merchantman Delisle (3,478 GRT) on the 19th and the same day the British Penolver (3,721 GRT) the very same day, on the 19th. While underway south in the Atlantic, U-220 was spotted and attacked by planes from USS Block Island. Soon, a wave of Avenger and Wildcat came out the same 28 October 1943 to finish her off with bombs, DCs and gunfire. After a direct hit, she was lost with all hands.


80-G-700007: Battle of the Atlantic. U-233 (German Type XB Submarine) sinking after being rammed by USS Thomas (DE 102) in the North Atlantic, 5 July 1944. Photographed from USS Thomas’s bridge. Note mine chutes on the submarine’s foredeck, a feature of the type XB U-Boats. Official U.S. Navy Photograph, now in the collections of the National Archives. (2017/02/14).

U-233 was commissioned on 22 September 1943 and made ready for operations under command of Oberleutnant zur See Hans Steen. She was assigned to the 4th U-boat Flotilla for training and for advanced training and operaions with the 12th U-boat Flotilla (1 June 1944). Her first and only war patrol started the day she departed Kiel on 27 May 1944. Like her sister U-233 her mission was to lay mines off Halifax. But she never made it there.
On 5 July 1944, U-233 she was caught by USS Card’s (CVE-11) hunter-killer group. At first spotted by sonar, she was depth-charged to the surface and fired on by USS Baker (DE-190), and finished off by ramming, sunk by USS Thomas (DE-102). 32 went with her to the bottom but 29 were rescued by the escorts.


U-234 was damaged during construction (RAF raid), but she was launched on 23 December 1943, but during her completion iot was decided to not use her as minelayer but transport sub right off the bast. Her mission would be to bring to Japan strategic assets.

The most secret U-Boat mission of WW2
She was relocated in Germaniawerft yard, Kiel for reconstruction as transport by 5 September 1944, and had a snorkel added. 12 of her 30 mineshafts receiced special cargo containers fit for them, and held in place by the mine release mechanism. Her standard keel load was replaced by extra cargo, first planned to be optical-grade glass and mercury while her upper-deck torpedo storage compartments on each side received extra cargo containers. She would have the most interesting career of U-Boats.
It’s the special commission “Marine Sonderdienst Ausland” which determined the exact nature of her caro by late 1944, and officers were informed of their mission Japan, which when complete brough her to have 240 tons of cargo, and all the fuel fuel and provisions to make a nearly 9-month (epic) voyage.

U-234 carried not only mercury and rare materials, but mostlt critical intel documentation, engineering plans, blueprints, and parts of the most advanced radars and weapons systems designed by Nazi Germany with a single goal in mind, allow Japan to continue the war. Ampong others she carried the latest German electric hoping torpedoes, an entire Me 262 jet in crate, as well as a Henschel Hs 293 glide bomb (the first antiship missile) and 550 kg (1,210 lb) of uranium oxide for the Japanese nuclear program. In the manifest she was decribed also as carrying “50 lead cubes with 23 centimetres (9.1 in) sides, painted “U-235″” in the cylindrical mine shafts, the “U-powder”.

Cargo and Personal to win the war
U-234 started pos-completion trials near Kiel, and was prepared for the trip and carrying also “VIPs”: The twelve passengers lits including German general Ulrich Kessler (Luftwaffe) with the task of providing help to the Japanese industry to serial built the new aicraft and missiles and ensure liaison with Berlin, four German naval officers, civilian engineers and scientists as well as two Japanese naval officers acting also as translators. Kay Nieschling (a Naval Fleet Judge Advocate) was to try to find a spy in the diplomatic corps in Japan (Richard Sorge ring). Also was aboard Heinz Schlicke, a radar specialist also specialized in infrared systems and radar countermeasures. There was also the director of the Naval Test Fields in Kiel and August Bringewalde, Messerschmitt’s production specialist for the Me 262 production. The Japanese officers were Lt. Cdr Hideo Tomonaga, IJN, and naval architect/submarine designer arrived in Germany back in 1943 on I-29 and Commander Shoji Genzo, aircraft specialist, former naval attaché, also coming back with tons of documentation after his long stay in Germany.
So this was, by all means, a very strategic mission with the potential for Japan to return the fate of arms.

Trials in Norway
U-234 thus departed Kiel for Kristiansand, Norway on the evening of 25 March 1945. At that stage, the U-Boat war was over, air supremacy was total and travelling while surfaced was perilous at best. She was accompanied by escort vessels plus three Type XXIII coastal U-boats until reaching the Horten Naval Base on the 27th. After eight days of trials including testing her snorkel in safe area, she accidentally collided with a Type VIIC U-boat also making her trials in the vicinity. Damage was light, she ws patched and declared ready to undertake her trip to Kristiansand, (5 April) for more repairs, replenished her provisions, fuel and prepared for the

The trip
U-234 departed Kristiansand on 15 April 1945, submerged at snorkel depth for 16 days untik her commander Kapitänleutnant Johann-Heinrich Fehler estimated she passed the “danger zone” and was ready to run surfaced. He also expected to cross a severe storm to hid him out. Captain Fehler soon found the ideal and safest way to travel: Two hours surfaced at the dead of night and the rest submerged with snorkel. However of the tip was without incident, the Goliath tranmitter eventuall fell silent, revealing some clues about what happened back home. The Nauen station followed, as the Kriegsmarine HQ was just captured by the allies.
On 4 May, while surfaced, U-234 received a partial British broadcast and learned later by American radio Admiral that Karl Dönitz was now at the head of the state after the death of Adolf Hitler. U-234 surfaced eventually on 10 May and received Dönitz’s order to all U-boats still in operation, to surface and surrender to any encountered Allied forces. Fehler however sensed a trick and contacted nearby U-873 for confirmation.

U-234 having no more purpose, she could sail either to a British, Canadian or U.S. port and eventually he decided to head for the US east coast, believing United States cuqtody to be less harsh than British or Canadian one, even to be repatriated quickly. He radioed on 12 May his intention to sail to Halifax, Nova Scotia as a ruse, whereas he set sail for Newport News instead, in Virginia. Not willing still to leave valuable assets to the former enemy, he dismounted and thrown overboard his Tunis radar detector, Kurier radio communication system, Enigma machine and documentation as well as any other classified files. Meanwhile informed, the two Japanese passengers decided to commit Seppuku using poison and were buried at sea.

The radio ruse was eventually found out by US authorities after a spotting and two destroyers arrived to intercept U-234. On 14 May 1945, while off the Grand Banks, Newfoundland Captain Fehler and his officers saw first with their binocular the prow of USS Sutton, steaming at full speed. The sky was pristine blue, with a vibility to dozens of miles. USS Sutton’s crew soon launched a boarding party to discuss the surrender terms and take control of the boat. They were ordered to sail for Portsmouth Naval Shipyard and be interned, joining there U-805, U-873, and U-1228.

News of the “secret U-Boat” immediately became a national sensation, widly relayed by new medias. The press was baffled by her high-ranking German passengers and even before she arrived, journalists crammed into a small boat came for a close look at the submarine. US intelligence was almost immediately at hands with everything of use, starting an inventory. It was done on 19 May. What they listed on were drawings and medical supplies as well as composite steels, instruments, optical glass and materials such as brass, lead, mercury, plus its carefully packed 1,200 pounds (540 kg) of uranium oxide. This load remained classified until the end of the Cold War.

This captured, in the frame of Operation paperclip soon generated an abundant litterature, still ongoing to this day, including radio broadcasts, TV documentaries, and some pseudo-historical and conspirationist works recently. Joseph M. Scalia claimed the uranium was in gold-lined cylinders in his “Hitler’s Terror Weapons”. Carl Boyd and Akihiko Yoshida speculated the uranium was to be used as catalyst for the production of synthetic methanol for aviation fuel, not to be military grade one for the Japanese nuclear program. But it was later discovered that there were cyclotrons in Japan and indeed an atomic bomb program. The Uranium was likely recuperated to be studied and used at the Oak Ridge diffusion plant. It was estimated just 20% of what was necessary to create a fission weapon.
After she was studied, U-234 having no longer purpose was disposed of by the USN: She was torpedoed in exercize by USS Greenfish (Gato class) off Cape Cod, Massachusetts, 20 November 1947.

HDMS Niels Juel (1918)

HDMS Niels Juel (1918)

Denmark Coast Defence ship laid down 1914, rebuilt 1918, 1929, 1937, captured 1943

HDMS Niels Juel was a Danish warship built in WWI, named after probably the most famous Danish admiral of the 17th century, winning a battle against Sweden. Initially she was laid down in 1914, and classified as a coastal defense ship, but later as an armoured cruiser, and rearmed as such in 1918. She was modernized in 1929 and 1935-1936. During World War II, HDMS Niels Juel served served with the Danish Navy, neutral but occupied by the Germans. Her fate was settled at the Battle of Isefjord 29 August 1943 by the Luftwaffe. She was beached and captured, re-floated and recommissioned as KMS Nordland, but scuttled again in 1945. #ww1 #ww2 #danishnavy #nielsjuel

Design development of Niels Juel

A Coastal Battleship (1914)

Niels Juel first 1914 design, with two 305 mm guns (12-in).
Defined as the new Coastal battleship, HDMS Niels Juel was laid down in September 1914. She was sightly larger than Peder Skram, but featured a more modern propulsion, with mixed coal/oil boilers and a heavier armament: Two 12-inch guns (305 mm) as initially planned. Most importantly she had a taller hull with better seakeping, fit for the high seas, rather than the monitor-like low freeboard of the previous Peder Skram. The Krupp guns however were seized by the German army before delivery in August 1914 and soon converted into railroad artillery.
Her initial data comprised the following:
Displacement 3,800/4,100t, two 12-in(305mm) guns in single turrets for and aft, eight 120mm QF guns (as of 1917) in side casemates open deck mounts, two 75mm AA guns admiship.

The previous HDMS Peder Skram in 1908

Therefore, not only construction was stopped and resumed slowly, but the ,naval staff had to rethink the design entirely. In addition further delays came with the Copenhagen navy yard being busy trying to maintain the existing fleet now the country had to provide an extensive neutrality patrol service to protect its assets and trade. After the war ended the Allies forbade Krupp to honor the contract, leaving the Danish Navy little choice but to completely change the original coastal battleship layout into something else.

Redesign as armoured cruiser (1918)

The Danish admiralty looked at other providers for the main artillery, not willing to compromise the design too much, but they were opposed by the Danish parliament, which estimated that heavy guns should look theatening to neighbours, notably Germany, and instead looked to purchase ten 150mm (5.9-inch) guns from Bofors, Sweden. Thy also asked the design should be changed into a training vessel instead. The tall and roomy hull could help in this already. The main guns had to be at least shielded, placed in a pair forward and superfiring pair aft, with three more on each broadside amidships. Thus, apart its stocky and tall appearance, Niels Juel was much closer to a cruiser.

Procurement of the guns, before Sweden accepted, was difficult. France, UK and Sweden competed and their offers rejected until an agreement was found with Bofors. A secondary armament of 120 mm (4.7 in guns) was asked for by the Admiralty, based on 1917 post-Jutland battle reports. They showed this intermediate, quick-firing caliber was still quite effective. But there was no room left and it was dropped, as the proposal to keep four 15 cm and the rest in 12 cm for the sake of supply and fire homogeneity.
Also a pair of 57 mm (2.2 in) A.B.K. L/30 anti-aircraft guns was chosen to complete the panoply and procure AA defence. They were to be mounted abaft the funnel. Like the original, she kept a pair of submerged 18 in (457 mm) torpedo tubes.

Design-wise she was more an armoured cruiser and was seen as such in most publocations of the day. The term “coast defence ship” however is retained by most due to her limited speed. Two points has been privileged in the design, armament and protection to the detriment of speed indeed. Being stillinternall cramped, she could not be equipped with a generous powerplant, and her ration of lenght-width could not support high speeds anyway, even compared to most pre-dreadnoughts at 15 knots.

This fit her coastal duty and confirmed her “classification”. The new design was eventually approved in 1920. She had been originally laid down on 21 September 1914 at the Orlogsværftet (Royal Danish Naval Shipyard) in Copenhagen, but construction proceeded slowly and she was launched on 3 July 1918. This launch was interrupted by a stop mid-way through the slipway, for over an hour. This was before she could be freed and slide into the water. But Construction was halted a few months later and her design reconsidered. Construction only restarted in 1920 to a new design. She was at last commissioned in May 1923, nine years before being laid down.

Plan of the construction/modernization of the Niels Juel

Hull and general design of the “Artilleriskibet”

Short (90 m) for a 16.3 m width, almost 1/5 ratio, her hull was divided into 10 watertight compartments and fitted with a double bottom for extra ASW protection, another adjustment inherited from WW1 lessons. The ship was called by the Danes themselves as an “artilleriskibet”, almost a gunboat in essence. Her final appearance diverged greatly from the first draft, with a tall superstructure and high freeboard, forecastle, unique funnel and tower bridge atop a communicating tube as well as her armament. The conning towwer forward of the bridge was two-stage, with the wheel section lower forward and firing station higher behind, in tandem.

She had a single mainmast on top of her military mast tripod and a single pol mast aft to support radio cables. She had three heavenly spaced sponsons guns, two fire spotting stations fore and aft with two telemeters (type unknown) atop her forward bridge and on the aft platform. He tripod supported a firing direction top.
She also had three projectors for night action: Two on the tripod, two aft on the platform close to the aft telemeter.
Her crew comprised originally 310 officers and ratings in 1924, but was expanded to 369 in WW2 due to her numerous AA additions.
They were evacuated by eight service boats: Four amidship under inner davits and four aft under outer davits.

Armour protection layout

She was protected by Krupp cemented armor made by Bethlehem Steel after an international tender for procurement, about 195 mm (7.7 in) on the belt, down to 150 mm (6 in), with 175-165 mm transverse bulkheads (6.5-7-in) to close the citadel. The shields ranged from 10 to 50 mm for the frontal arc (2 in) and the deck was 55 mm (2.1 in) thick while the conning tower was 170 mm (7 in). Overall, this was an excellent protection, even for an armoured cruiser, giving it was way superior to her own armament.
So in short:
Belt: 155–195 mm (6.1–7.7 in)
Deck: 55 mm (2.2 in)
Gun shields: 50 mm (2.0 in)
Conning tower: 170 mm (6.7 in)
Bulkheads: 165 or 175 mm (6.5 or 6.9 in)


There was aboard a single pair of vertical triple-expansion steam engines, driving two shafts, with three-meters diameter and three-bladed propellers. These steam engines were fed by four Yarrow boilers with superheaters, two pairs running on oil, and the second on coal. This also was a modification of the 1914 design, which was all-coal, and a lesson of WWI. The 6,000 indicated horsepower (4,500 kW) allowed only 14.5 knots (26.9 km/h; 16.7 mph) but on trials, HDMS Niels Juel was able to reach 16 knots. Her internal mixed capacity still allowed a generous 6,000 nautical miles (11,000 km; 6,900 mi) range for Denmark’s limited coastal waters, at 9 knots. She could patrol around the entire coast and back, with extra incursions in Noorwegian waters and through the Skagerrak along the Baltic German coast. This also fit her role as training cruiser.


Although certainly less potent as deterrence than 12-in guns, her final armament was quick-firing and still capable to inflict damage to any incoming ship, provided she was not out-ranged. For her limited size, it was quite impressive nevertheless, and made her somewhat a “crowded” ship.

Main: 12x 15cm Bofors (1923)

There is little information about these Bofors models other than by default of Krupp, they were extremely close in design and performances to the well-known German 15 cm SK L/45.
We can deduce they were made of an A tube with two layers of hoops and an horizontal sliding-wedge breech block and Hydro-spring recoil. They used separate loading quick fire shell, for a 5-7 rpm,
Muzzle velocity of circa 840 ms (2,800 ft/s). For each broadside they could deliver six shells, four in chase, four in retreat. Ammunition aboard supply unknown.

AA: 2x 5.7cm (1936)

There was no secondary armament so they swapped directly to a pair of rapid-fire guns of small caliber to deal with aviation, also usable against ships and as saluting guns as well. But there is no information about these before 1936 when they were implemented. They assumed to be Swedish Bofors (later evolved into the 57 mm/60 (2.25″) SAK Model 1950, itself a scaled-up version of the famous 40mm Bofors).


She had two beam, submerged torpedo tubes installed, firing type H torpedo fitted with a 121.5-kg (268 lb) warhead, hitting their mark up to 8,000 meters at 27 knots.


HDMS Niels Juel in 1938
Niels Juel’s first operational cruise started in May 1923. She made numerous visits and later state visits as Royal Yacht, carrying the Royal family. In this role she toured the Mediterranean in 1929.
-1929-1930: At the same time she received modifications: The two three-meter rangefinders were transferred to older ships like the Peder Skram and Olfert Fischer and she received instead a single modern modern Barr & Stroud 3.66 m coincidence rangefinder, replaced a year later by a German Zeiss 5 m coincidence rangefinder.

-She was modernized in 1935-1936, and the fire-control systems were changed again, with the tripod mast replaced by a pole mast, two-stage director-control tower. She received then a Dutch Hazemeyer gunnery director and analog gunnery computer with three Zeiss 6 m rangefinders. The 57 mm AA guns were replaced by ten Madsen 20 mm RK M/31 autocannons in five twin mounts.
Smoke screen projectors were fitted at the stern. She would also received in 1937 seven twin mount 8 mm (0.3 in) Madsen R.K. L/75 M/37 machine guns.
Her aft pole mast was replaced by two lattice extensions aft of the funnel’s top cap, supporting the wireless radio cables hanging from the mainmast forward.
-In early 1941 she received an extra pair of 40 mm Bofors AA guns (single) and in 1942 ten faster-firing Madsen 20-millimeter L/60 M/41 autocannons fitted in place of the older models.

Profile in WW2, with neutrality markings (src alchetron). In reality her livery was brighter than this dark grey shown here. Personal HD profile coming.

⚙ specifications

Displacement 3,800 long tons (3,861 t) (standard)
Dimensions 90 x 16.3 x 5m (295 ft 3 in x 53 ft 6 in x 16 ft 5 in)
Propulsion 2 shafts VTE, 4 Yarrow boilers oil/coal 6,000 ihp (4,500 kW)
Speed 14.5 knots (26.9 km/h; 16.7 mph)
Range 6,000 nmi (11,000 km; 6,900 mi) at 9 knots (17 km/h; 10 mph)
Armament 10 × 150 mm (5.9 in), 2 × 57 mm (2.2 in), 2 × 450 mm (17.7 in) TTs
Protection Belt 155–195, Deck: 55 mmn Gun shields 50 mm, Conning tower 170 mm, Bulkheads: 165 or 175 mm
Crew 310–369

HDMS Niels Juel’s Career

Early Interwar Career 1924-1939

HDMS Niels Juel made her sea trials following her commission in 1923 and her shakedown cruise on 28 May with Crown Prince Frederick aboard. The brand new ship visiting the Faeroe Islands, Bergen in Norway, Leith in Scotland and Gothenburg in Sweden, before before being back home in Stockholm on 6 August.
On 21 October, after working up some issues and preparing, she made her first training cruise. She had for port calls Dartmouth (UK), Cadiz (Spain), Madeira (Portugal) Cape Verde Islands, and went south-west to South America.

On her return trip she was battered by quite a severe Atlantic storm after leaving the Azores. She rocked so much her rudder chains broke and she became unable to steer. She had to resume her trip by using output alone, turning by alternating her steam engines, until until emergency steering was rigged to resume and trip home, arriving on 23 February 1924. After repairs in Plymouth she became flagship, gunnery training squadron. Later she became flagship of the general training squadron.

In 1925, she made a short baltic cruise, visited Finland (taking part in a parade and saluting), as well as nearby Estonia, Latvia and Germany. In 1926 she cruised to the Faeroe Islands and Iceland with the royal family aboard. She was also the royal yacht for a state visit in Finland in 1928 escorted by the cruiser Heimdal, making another round of gunnery salutes as part of the Danish Squadron.

No record for 1926n 27 or 1928, but in 1929 she made an intensive training cruise into the Mediterranean making port calles in France, Spain, Italy and Libya, and Portugal on her way back, showing her range was totally adequate for these trips. She was back into her flagship, training squadron routine for the remainder of the year but on 22 May 1930 regained her status and function as royal yacht for a tour of the Faeroes and Iceland, still training naval cadets. In 1931, she made refuelling stops in her second Mediterranean cruise, and became the first Danish warship ever to visit the Black Sea via Istanbul, and stopped in Odessa. On her return trip she stopped in Greece, Italy, Algeria, and France.

Niels Juel was eventually decommissioned on 3 September 1931. It seems she was in limited commission in 1932-34 (photos shows her at sea), and she was modernized in 1935 and 1936, recommissioned on 9 July and spent the rest of 1936 in sea trials and working up her new crew.
1937 saw her as flagship of the Danish squadron in the Fleet review in Spithead for the coronation of George VI, 20 May 1937. She later took part in a fleet exercise which ended in Helsingborg, Sweden. In 1938, she led the Danish torpedo boat flotilla to Turku in Finland by August, stopped in Sønderborg (Denmarkp in September and pet here the whole training squadron. In 1939 it was planned her first training cruise to the United States cilumating with the New York World’s Fair by May. But this was cancelled due to rising tensions. She stayed trining with HDMS Peder Skram until July 1939.
By late August, she prepared a small cruise to Oslo, but it too, was cancelled. The admiralty order to prepare her for war, starting by having all shell fuzes setup for combat. Her training crew was fully completed, she received additional AA MGs soon and she was fully mobilized, joining the fleet near Aarhus. Winter ice however forced her back in Copenhagen by January 1940. The crew was soon given leave but recalled on 8 April and the 9th, the Germans invaded the country while her crew was still not all aboard. After the country surrendered after a few hours of fighting, the Germans allowed the Danes to keep their fleet and resume training in Danish waters.

Neutrality (1940-1943)

The only waters, where the German occupying power had allowed such training cruises to be held by the ship limited her movements. In between limited fuel supplies (requisitioned, Niels Juel was not frequently at sea. During the was she was under command of 49-year-old ship captain Carl Westermann, which knew his ship well. He had for several periods been commander and second-in-command aboard, and also had several years’ experience as a torpedo boat commander.
But it was not just an experienced captain who decided to escape with ship and crew to Sweden on 29 August 1943. Carl Westermann had been a member of the Folketing since 1933, and earlier in the year 1943 had been elected as the 1st Deputy Chairman of the Folketing. The lead-up to 29 August 1943 was, from the Danish side, a clear no from the government and people’s government to continued cooperation with the German occupying power, and the increased German demands. One can therefore almost see something symbolic in the fact that the fight between NIELS IUEL and the German armed forces, from the Danish side, is led by the 1st Deputy Speaker of the Folketing, in his capacity as ship’s captain.

Operation Safari (August 1943)

In 1943, Danish resistance to German rule hd ramped up considerably and local German authorities started to crack down on some groups, also instituting martial law on 28 August 1943, then like they did in France by November 1942, they moved to seize the Danish fleet in Copenhagen at dawn on the 29th. This übung was codenamed Operation Safari. On the 27th already, Captain Westermann was warned by the Admiralty that somehing was cooking up. The following evening he held a meeting with the ship’s officers and they agreed that ailors were to remain aboard and that the ship was prepared to leave at the shortest notice. On the 28th he still awaited orders, but on the morning of August 29, he anchored in Holbæk.
Niels Juel was preparting for departure at 4:00 am, when Carl Westermann received the radio order fro the Danish admiralty to steam to be interned in Sweden. At 04:20 the order also precised, in case she was stopped or disabled, to sink the ship.
Niels Juel left Holbæk around 06:00, setting a course for Sweden. The Germans however caught the message and sent planes, until they spotted her just after departure.
Before she could exit the Isefjord, Westermann learned the Germans claimed mining the exit -which was a bluff- to try to stop her. He proceeded anyway but soon spotted three German ships in the distance: These were the torpedo boat T17 and two E-boats, dispatched in interception. Soon also the Luftwaffe was sent in, and Ju-87 Stukas appeared.

Battle of Isefjord

From 08:55 till 09:35 Niels Juel was repeatedly attacked by German aircraft south of Hundested. A few Stukas based in Denmark dropped bombs and used strafing. None of the bombs hit Niels Juel. There was however some rude near-misses, which badly shook her hull and and knocked out electrical power; Hull plating and bulkheads were also deformed and unhinged. Meanwhile the crew manning the AA put up quite a fight, but the machine guns could do little. Pilots respected however her two 40 mm Bofors, backed by several 20 mm guns. it is not known is she damaged any of her assaulters, but none was reported down. In all she had five Danish sailors injured, rather seriously, no dead until artillery quartermaster H. E. Andreasen a few days later from the injuries he had sustained in the last air raid.

Realising there was little hope of reaching Sweden now, between these air attacks and “greeting committee” of three fast TBs blocking his way, Westermann decided to save his crew and run his ship aground near Nykøbing Sjælland. The crew tried to scuttle the ship by using the explosive charges, but the attempt failed. Next it was decided to flood the magazine, and all the sea-cocks to flood the rest of the hull and systematically destroying all sensible or useful equipment before the Germans could takje over her. Indeed soon the TBs arrived on the scene and capttured the entire crew.
Before this, Commander-in-Chief Carl Westermann, received unconfirmed information that the Danish fleet at Holmen, Copenhagen had been sunk/scuttled in the morning hours.
At 10:48 NIELS IUEL was effectively beached, sea cocks opened, and she slowly settled to the bottom. The crew was made prisoner only the following day, on August 30th, leaving them plenty of time to scuttle the ship as best they could.

Kriegsmarine service and Postwar Fate (1944-52)

As shelied grounded, a Danish salvage company was sent by to inspected the wreck only a few days after her sinking. They failed to see see any damage to the hull, rudder or propellers, so ensuring she could be refloated. But they noted she was still heavily flooded, up to 1.5 meters (4 ft 11 in) below the armored deck. The Germans wanted to have her rised and rebuilt her likely into a Flakschiff, and commanded a German company to proceed. By October 1943, they did so using pumps, and she was refloated and towed it to Kiel, Germany, for repair and transformation.
She was however disarmed and renamed Nordland, and commissioned into the Kriegsmarine in September 1944, not as Flakschiff but stationary training ship based in Stolpmünde (modern Ustka, in Poland). Her removed armament was not lost, it was used for close defense of a number of German artillery positions on the west coast of Jutland.

On 18 February 1945 she steamed to Kiel to avoid capture by the raidly advancing Russian army. By 3 May 1945 she was scuttled in the Eckernførde inlet. The wreck was partially dismantled by unauthorized scrappers before the Danes officially sold the wreck to a German company that BU her in 1952, after removing everything above the sea bed and left the bottom wreck, no longer a navigation hazard, still laying under 28 meters (92 ft) of water.

Read More

Admiralty Model of the Niels Juel at the Royal Arsenalen Museum (2017 photo)


Westerlund, Karl-Erik (1985). “Denmark” in J. Gardiner Conway’s all the world’s fighting ships 1906-1921
Campbell, John (1985). Naval Weapons of World War II. Annapolis, Maryland NIP
Wisman, Tom (2018). “Niels Juel: ‘A Funny Little Danish Warship'”. Warship 2018. Oxford, UK: Osprey.


On navalhistory.dk
navalhistory.dk/ Niels_Juel
navweaps.com/ swedish ordnance
on navypedia.org/

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WW2 Imperial Japanese Cruisers

Imperial Japanese Navy Cruisers of WW2

The fleet’s spearhead

In December 1941, the most valuable asset of the Imperial Japanese Navy, after the aircraft carriers of the combined 1st air force (Kido Butai), were its Cruisers. Indeed, contrary to the older, slower battleships, cruisers were built along along the interwar and perfected until stopped during the war itself, when fewer resources were available.

All in all, despite having formidable offensive assets, IJN cruisers performed actions in dispersed order depending of their age and capabilities. The real spearheading ones were only twelve: The four Myoko, the four Takao and the four Mogami. They were the most recent, best armed, largest of the IJN and indeed took part in the most offensive fleet units of WW2 in the Pacific.

The older 1920s vessels of the Tenryū, Kuma, Nagara and Sendai classes were stil transitional WWI designs which were arguably obsolete in 1941 and were sent to aid eny convoy which needed protection; thus logically sidelined and never used in first line units. The experimental Yubari followed that path, but the more potent Furutaka and Aoba classes at least saw more frontline action. Wartime vessels such as the Tone were in effect the last “heavies”, joining the pack, but the four Katori were essentially schoolship with little military value, and the four Agano were rather more escorts than frontline cruisers.

Special mention to the never-built B-64 though. These “large cruisers” to keep the US denomination adopted for their Alaska class, proven to be an imaginary threat were indeed planned by the IJN high command planning the end of peactime limitation, as a “cruiser hunter”.

Legacy: WW1 cruisers still in service

In December 1941 there were still a surprising number of WW1 vessels still listed as active, dating back from before the great war. On paper, this was even impressive and only comparable to the Royal navy’s C and D class cruisers. There were of course those of the 1918 plan which were the best known, the oldest of which being the two Tenryu class launched in 1918, but the following Kuma and Nagara (11 cruisers) designed as destroyers leaders were completed at the time the Washington treaty was signed. They are seen in the later part of this article;
As for older cruisers, the list was comprehensive, but the Washington treaty forced their scrapping and/or conversion to other roles. Not willing to scrap what for them was perfectly valid ships, paid a high price compared to the country’s GDP, they were maintained in service by using the exemptions of the treaty: Training and Miscellaneous ships (like minelayers).
And thus a remarkable number of these “antiques” in 1942 were still proudly flying the hinomaru.


If the four Kongo class were the last and best known, reconstructed twice in the interwar and gradually converted as fast battleships and thus not counted here. The older Kasuga class, Ikoma and Kurama class were classed as armoured cruisers (from 1921 for the latter).

Armoured Cruisers:

Asama class: Launched 1898, Asama was converted as a training ship in 1937 (BU 1947) and Tokiwa as a minelayer by 1928.
Yakumo: Launched 1899, she became a coast defence ship (full detail later)
Adzuma: Launched 1899, was also converted as a coast defence ship, and doubled as trainign ship as Yakumo.
Izumo class: Izumo and Yakumo, Launched 1900 were 9750t ships with the same status: TS in peacetime, coast defence ship in wartime.
Kasuga class: Kasuga and Nisshin were “1st rate cruisers” and used as training ships from 1927 as new vessels took their place. Nisshin was expended as target in 1936 but Kasuga only retired in 1942. She was sunk in Kure the same day as the two Izumo in July 1945 (see later).
Kurama class: The former battlecruisers, reclassed in 1921 as “1st rate cruisers” were considered during the Washington treaty too valuable to keep even as training ships. They were ordered to be scrapped, which was done in 1923, to quite some frustration from the naval staff.

The IJN Yubari (here colorized by irootoko Jr) at Sasebo just completed in 1923. This strange prototype light cruiser marked the rebirth of the IJN after the Washington treaty. She really was built not to fill a precise requirement (but of a fleet scout), but merely to test new weight-saving construction techniques will would allow the IJN naval staff to get “more with less”, doing better than the (US-British) competition in armament on smaller tonnages. The Tomozuru and 4th fleet incidents would shatter these illusions.

Protected Cruisers:

Smaller and of an earlier design these vessels were improper for training ship conversion. Re-rated as 2nd class cruisers in 1921, their career was shortened, except for three.
Chitose class: This 4760t, 1898 ship was discarded in 1928, sunk as target 1931
Niitaka class: Niitaka and Tokiwa were 1902, 3,366 tons cruisers no longer active: The first was lost in a typhoon in 1922 and the second hulked in 1930, sunk in 1944.
Tone: This 1904 4,100 ton cruiser was discarded in 1931, sunk as target in 1933.
Chikuma class:
These had a more interesting career. Still “young” in 1922, they were reboilered and rearmed to extend their useful life. Chikuma due to tonnage limits was discarded in 1931, Hirado in 1939 and Yahagi hulked in 1940 so they took no part in the hostilities, but both survived WW2 nevertheless.

Postwar cruiser development: Yuzuru Hiraga’s design school

Baron Yuzuru Hiraga was one of the most influential (if not the most) of the Imperial Japanese Navy in the interwar. Born in Tokyo, grewing up in Yokosuka, Kanagawa (his family was from Hiroshima) he graduated from Hibiya High School and was in the engineering department of the Tokyo Imperial Universityby 1898. As specialist in marine engineering. Draft in the IJN while still being a studen in 1899 he graduated in 1901 as sub-lieutenant and started working at the Yokosuka Naval Arsenal a design engineer.

A lieutenant on 28 September 1903 she was transferred to Kure Naval Arsenal in 1905 just as the Russo-Japanese War started. He was soon sent to the allied United Kingdom for extra studies of British designs, leaving Yokohama for the Pacific in January and also visiting the United States west to east, and crossing the Atlantic Ocean to London in April 1905. By October, he became a member of the Royal Naval College in Greenwich, having the most immediate immersion into the latest techniques in warship design. Graduated from there by June 1908 he spent six months touring various shipyards in France and Italy for an extra insight,nwriting many reports befire arriving in 1908 back in Japan. By September her became professor of engineering, at Tokyo Imperial University, promoted to lieutenant-commander on 1 October.

In 1912 he was part of the design team in charge of the design for the battleship Yamashiro (Fuso class) and conversion of Hiei from battlecruiser into a battleship. He also worked for the Kaba-class destroyers designed and became commander on 1 December. In 1913 he became Director of Shipyards for the Imperial Japanese Navy, a very coveted title comparable to CNO, and awarded the Order of the Sacred Treasure on 28 November, and a new time by November 1915 as he managed to speed up the efficiency of Japanese shipyards under heavy strain to provide ships to the allies (and another award on 25 February 1926).

In 1916 he was the chief engineering director behind the “Eight-eight fleet program”. He focused on a new breed of high speed battleships and cruisers. On 1st April 1917, now ranked captain and rear admiral from June 1922 he closely followed discussions leading to the Washington treaty with dread. On 7 November 1920 he was awarded the Order of the Rising Sun for his innovative deisgn for the cruiser Yubari, his first really 100% own project.
He was soon appointed a technical advisor to the Japanese delegation sent to the Washington Naval Conference until August 1924. Back home he was promoted to the head of the Imperial Japanese Navy Technical Department and vice admiral in 1926.
He assembled his own design tem around picked-up engineers to create a new fleet within the Washington Naval Treaty boundaries, severely restricting Japanese designs and forcing him to take many innovative design approaches (mostly saving weight) for cruisers and destroyers. His shiped became extraordinarily powerful for their tonnage, using assembly and construction techniques among the most advanced at the time. His famous work was to bring about heavy cruiser better armed than the competition while still well below the 10,000 tons limit (about 8,500 to 9,000 to plan for future additions).

However perhaps enboldened by these enegineeing feats, the Imperial Japanese Navy General Staff often ordered that more weaponry despite Hiraga’s objections over strength and stability. The Mogami-class cruisers were perhaps the most striking exampkle with no less than 15 6.1-inch guns over a 8,500 tons tonnage. In fact these feats only came through “generous” underestimation of their true displacement as well as sacrificed in hull strenght and stability as shown by the Tomozuru incident. By 1929, his last project, the planned Kii-class battleship (never completed) was ended abruplty by the naval staff and retired from active military service in 1930, now just an advisor for Mitsubishi shipyards, in part tired and disgruntled by the attitude of the Navy.

In April 1934 despite all his previous warnings he was part of a board of inquiry after the Tomozuru Incident. His reputation suffered even further in the Fourth Fleet Incident, forcing the Fubuki-class he designed for a rebuilt after a typhoon. Nevertheless he managed to clearly establish his own warnings and was eventually released, and even appointed in the design team in charge of the Yamato.
In December 1938 he became President of the Tokyo Imperial University and conducted a “Purge” of those having liberal political doctrines. On February 17, 1943, Hiraga died at Tokyo University Hospital after a pneumonia, posthumously awarded with the Grand Cordon of the Order of the Rising Sun and kazoku peerage as baron. His grave is now located at the Tama Reien in Fuchū, Tokyo.

The 1934 Tomozuru incident and consequences

As seen above, both this incident, compounded with the 4th fleet typhoon drama, was a incident which implied a torpedo-boat of the Chidori class. Japan like Italy and Germany looked at TBs as a way to create more warship tonnage out of the authorized destroyer tonnage. They could be useful notably in the confines of the China sea, Japan sea, Jorea sea or Pacific islands chains. But industrial limitations only generated two classes, the four Tomozuru (launched 1933) and eight Oroti class (1935). Soon the naval staff priorities changed for escorts, like the Shimushu class (launched 1939) followed by many more.

As for the incident, IJN Tomozuru incident happened soon after the ship entered service, on 24 February 1934. She joined the 21st Torpedo Flotilla at Sasebo and on 12 March 1934, departed for a night torpedo exercise with the IJN Tatsuta and he sister ship Chidori, marred at 03:25 by stormy weather and ordered to return to base. However soon radio contact was lost and her lights disappeared at 04:12, a signal she had probably capsized. A rescue started ten hours later, the capsized hull spotted drifting but there was none to save, 100 of her crew was lost in the rapid capsizing. She was was towed by Tatsuta to Sasebo for an investigation.

After weeks of intensive scrutiny it was established instability was the cause, as they played with the Washington treaty of 600 ton, but were given the armement of a 1,200 tons destroyer essentially. She received under Hiraga direction a lighter construction manking her top heavy. Their unbalance centre of gravity proved even higher than feared and efforts made to remedy it, as shown by her sea trials, by adding hull bulges on Chidori and applied to Tomozuru, and her sisters, with the added benefit of filling these with extra oil (so better range). However the incident happened when she was very low on fuel/water that would have used until then as ballast, hle having full ammunition load. The combination with what was perhaps a near-rogue or very high wave taken from a bad angle was probably the finishing blow. It was estimated that in her condition the situation was worse than on her sea trials.
Do note that the USN Farragut class lost two destroyers in a storm for the same reasons in 1944. They were less top heavy afte their partial reconstruction, but happened to meet the exact same conditions.

Whatever the details, the consequences were dramatic and far reaching. An immense cross-fleet investigation of all ships designed after 1922 was undertook, in search or similar design weaknesses. Recalculations (more detailed and realistic) were made with simulations of similar conditions which led to a rebuilting of the following ships due to their low metacentric height: The Aircraft carrier Ryūjō, the Mogami class cruisers, Fubuki, Akatsuki and Hatsuharu classes destroyers, submarine tender Taigei Minelayer of the Yaeyama, Shirataka, Itsukushima, Natsushima, Tsubame classes, minesweepers of the No.1 and No.13 classes and existing subchasers. The total cost was worth one or two battleships and had grave financial consequences for the IJN budget planification, delaying several program and shutting down projects.
It completely changed the naval staff initial assumptions over stability issues, and led to valuable lessons for future designs across the board. Superstructures were reduced, bulges added, over deck structures lightened, ammunition dug below decks, and armament downgraded in 1934-35. The Mogami-class cruisers were probably the most heavily modified of all these ships, at again, a cost superior to the construction of an extra cruiser.

The Tomozuru affair will bounce back with the loss of several Fubuki class in the 4th fleet incident, in a typhoon, for the same causes.
After 1936 no such incident ever occured again as the metacentic height was now one of the master data to put under scrutiny on all designs. Despite of these stability measures, the cruisers in particular were again compromised by the addition of countless AA guns in WW2, but no such capsizing happened ever again.

The 4th Fleet Incident

Japanese destroyer Hatsuyuki (Fubuki class) heavily damaged after Fourth Fleet Incident – 1935 (reddit)

On September 26, 1935, offshore east of Sanriku in the Pacific Ocean, the Japanese 4th Fleet while in training encountered an abnormal typhoon, 250 miles east of Sanriku coast, which damaged many vessels very seriously and also caused human losses. Bows were cut off from IJN Hatsuyuki, Yugiri, the new Japanese “Special-Class” Destroyers (serie started by IJN Fubuki). Many other ships were damaged or flooded (like Ryujo).
Waves far larger than first expected were the primary cause. But it was serious enough to be investigated, and new facts discovered. The main consequence, was a reinforcement of many ships across the board. The even confirmed tendencies in naval construction were risky at best, after the Tomozuru capsizing (which showed shortcomings in stability), and highlighted this time structural weaknesses across the board.

This day, the Blue Fleet (1st and 2nd fleets) was going agains the Red Fleet (4th Fleet, assembled temporarily). This large scame fleet manoeuver started in July, until late September (as planned). The rebuilt Yamashiro, Haruna, the Mogami Class and the Hatsuharu Class took part for the first time and much was awaited from their performances.
By late September, the Red Fleet crossed the Tsugaru Straits eastwards, and the Red fleet was expected east of Honshu Island to meet the Blue fleet. Weather degraded very fast from 14:00 on September 26, as a typhoon grew out of proportions, catching the fleet completely off-guard. The first largest waves simply knocked off the bridges of Hatsuyuki and Yugiri, the one of Mutsu was smashed, the front side Ryujo’s bridge too, and huge flooding followed, while IJN Hosho plunged so deep had flight deck was completely overwhelmed by huge waves, which crashed her deck and leaked into the hangar; All ships present suffered slight or heavy damage.
The Red fleet abandoned its maneuver and gathered off Shinagawa, Tokyo bay. On October 7 onboard IJN Hiei the staff made a reunion to assess the exercize and overall damage (she was the observing vessel of the maneuver). The incident was judged serious enough that authorities concealed it entirely, put all present sailors to secret, and this happened as Japan withdrew from the London Naval Conference soon after and went even more into secrecy.

Analysts were baffled as it was the first time any ship was so badly damaged by waves since the British destroyer Cobra split in half by 1899. This just confirmed worrying signs after the capsizing of Tomozuru, and put into question the whole Japanese shipbuilding practices. A commission of enquiry was setup in place and led an investigation, (also looking for scapegoats, this was a naval staff one, which deliberately asked engineers for more armament). It was determined first that the Special-Class destroyers. It was decided also to reinforce cruisers, notably those of the Mogami class, and even aircraft carriers. It shows for example that the Ryujo class, built on the below 10,000 tonnes design to go around the Washington treaty limitations (she was not considered as an aircraft carrier) was not a realistic prospect.
Plates that were recuperated and analyzed showed notably for the destroyer, many welding faults (or too weak bonds) and cracks developed after years of vibrations and intensive use. But since thos was merely a political matter, the naval staff looked to blame the shipbuilders and chairman Admiral Kichisaburo, assisted by Vice Admiral Isoroku Yamamoto and Rear Admiral Mineichi Koga. They heared notably Yuzuru Hiraga and his assistants.

On October 21th, 1935, a new special investigative committee for the improvement of the efficiency of naval vessels was established under the lead of Admiral Seizo Kobayashi, which was poised to find the most effective measures to deal with the structural weaknesses observed. These went on for five months and released a very detailed report in April 1936. It was also underlined that vessels appeared heavier than first designed, either when completed and fully loaded, or remarkably heavy after alterations. They established that welded ships proved to have reduced body strength also, and required extra internal bracing, better welding or riveting of some parts. Engineers put to the task found it was not easy to calculate and apply stresses in severe conditions. And the naval staff wanted these reinforcements must affect performance as little as possible. This became rapidly a daunting, hair-splitting and time consuming work and it was felt by some it would endanger National defense at that time. The government wanted to keep costs low, adding more strains in the effort.

Most of the smaller ships went into dock, their plateing and decks stripped and rebuilt, Bridges separated and re-braced. As it appeared welding was overused this immature technology. Also the Design process and construction techniques were reviewed across the board. Critical parts of the hull’s strenght were reevaluated and riveting reappared. They were used for example on Yamato. All these countermeasures efforts of all concerned bore frtui ultimately, with the last ship out of the yards in December 1938 already. They could therefore perform their missions without any further problems afterwards, but this caused immenses delays and extra cost to the fleet as a whole.
Rear Admiral Keiji Fukuda (later promoted to Technical Vice Admiral later) and Prof. Yuzuru Hiraga, assumed most of this daunting work, but this took a strain on the latter’s health, which soon retire from active involvement in naval construction afterwards.

This kind of event was not limited to the IJN however. Famously, the latter “had their revenge” in wartime: The U.S. Navy’s 3rd fleet under the command of Admiral Halsey, was heavily damaged by two typhoons during the Pacific War. Notably many ships were damaged, including some of the Essex-class carriers had their flight decks mushed and collapsed. On December 18th, 1944 in the Philippine sea, 3 destroyers capsized and sank, 18 vessels were badly damaged, 9 were slightly damaged, 183 aircrafts, 700 lives lost. It happened again off Kyushu on June 4th and 5th, 1945. This time, four battleships, two aircraft carriers, two light aircraft carriers, four escort carriers, three heavy cruisers, four light cruisers, and 17 other vessels were seriously damaged, most of the aircraft deck park thrown overboard or destroyed by giant waves. There too, draw consequences for US naval shipbuilding, notably by avoiding stability issues and oil-tanks consumption and supply procedures (this caused the loss of three destroyers in the first case). The Essex-class for example received “typhoon bows” when possible and the Midway class had them installed while in completion. Would this have changed things if the US intel had the knowledge of the 1935 incident ? Debate is launched.

Characteristics of IJN Cruisers

Cutaway of the Nachi class from “Imperial Japanese Navy Heavy Cruisers 1941–45: 176 (New Vanguard, 2011) by Mark Stille (Author), Paul Wright (Illustrator).

As already seen above through Hiraga’s design philosophy and incidents, the designs of early IJN cruisers (Yubari was a pre-Washington design, which stayed experimental, only to test new construction techniques) proceeded with two main concerns in mind: The heaviest armament possible, on the lighter displacement possible, and keeping speed at the top end of their class. Protection was not secondary. These early cruisers were not “paper cruisers” such as those French and Italians of the early 1920s. But there were clearly three eras to separate:
-The WWI program cruisers (Tenryu, the Kuma, Nagara and Sendai classes): These were scout cruisers, armed with single-mount pieces, at best with 2.5 in of armour on a partial belt.
-The post-Washington design cruisers: This included the new generation Furutaka and Aboa (4 ships), brand new designs based on the experience of Yubari but with heavy artillery of 8-in guns as in all navies of the time. And this included the Nachi class (designed in 1923), Takao class (designed in 1926), just much larger and better armed, and the Mogami class (designed in 1930), but revised after the London Treaty with 6-in guns.
-The Post-Tomozuru incident (1934): The Tone class (design revised in 1934 just after they were laid down), Katori class (which were school cruisers) and the WW2 Agano and Oyodo class intended as replacement for the WWI program cruisers.

The appreciation of design specifics for comparisons only concerned largely the Nachi, Takao and Mogami. Indeed the Furutaka and Aoba were merely “light cruiser” by displacement and an arguably lower armament than contemporary heavy cruisers and can be seen as steps towards the definitive IJN cruiser designs of the interwar, still testing many solutions. They are not representative of the whole picture.

Yubari was a prototype, and the design solutions were mixed with the need of a heavier armament proceeding by steps, single turrets on the Fututaka before rebuilding, and twin turrets with superfiring turrets with the Aoba. It was all-Japanese, since Britain ended its alliance with Japan in 1923. These “test cruisers” paved the way for a much more ambitious design, which was to this time answer to any regular British or US cruiser design of the time. The goal was simple: More guns and more, better torpedoes first and foremost. AA artillery was secondary.

Speed was paramount, and all this was to be done under the 10,000 tonnes limit officially as long as Japanese offices remained open to the west (which was no longer the case when the Yamato class was started). The fact Japan retired from the second London conference made it free to launch several reconstructions (like the Mogami class being the most spectacular) which implied also the Nachi and Takao, and naturally pushed their tonnage well beyond the 10,000 tonnes limit. In WW2 for example, they looked towards 14,600 tonnes or above. The Tone class (launched 1937) was even above treaties from the start, with 11,215 tonnes standard already and up to 15,600 tonnes later in WW2. They all gained bulges and were considerably reinforced structurally.


IJN Atago’s main turrets

Armament-wise, the cruisers went from six 8-in guns (203 mm) on the Furutaka-Aoba, to a staggering ten on the Nachi-Takao-Mogami (the latter before swap to 6-in guns); This made them the most gun-heavy cruisers of the interwar. The closest were the US cruisers adopting triple turrets (for nine guns) on the Northampton, New Orleans, and even the wartime Baltimore class. The European standard was eight guns in two twin turrets. The way to shoehorn a fifth turret however ment some sacrifices.

The hull was lenghtened, and the turret N°3 was placed between behind the superfiring N°2, meaning it was facing the bridge and had a more limited arc of fire, only potent in broadsides, but neither in chase or retreat. The mogami improved this as having the N°1 and 2 on the same deck level and N°3 raised on the superstructure, enabling more leeway and a six guns chase fire. The Tone were even more radical with a return to four turrets but all forward, a superfiring pair followed by two deck-level turrets facing the bridge. A unique approach enabling space aft for an air group. Something never seen in any other design worldwide.

The other shining point of the designs, purely out of Japanese newly developed night combat tactics with only cruisers and destroyers, favored an aggressive use of the torpedo. Indeed, from the Furutaka’s originl fixed tubes in pairs were substituted two quadruple banks at deck level after reconstruction, abd same for Aoba. But originally they could fire six torpedoes on either side.
The Nachi adopted these traversing banks early on, in four triple banks inside niches in the superstructure aft.

They thus passed from eight to twelve, six either broadside and reloads. This scheme was repeated on the Takao class (relocated amidships) and Mogami, Tone class as well. Many were later removed to spare weight and add extra AA. As for the light cruisers of the Agano-Oyodo they are to be compared rather to what they replaced. The Kuma-Nagara-Sendai had four twin tubes, four torpedoes on either broadside. The Agano planned as destroyer leaders had two axial quaduple banks (so also eight tubes) like on a destroyer, and this placement enabled more stability and a full broadside, twice the cruisers they replaced. The larger Oyodo due to her role had no TTs at all.

50 caliber 3rd Year Type 20 cm Gun 1 GÔ (No. 1)

This was the official designation for the main guns of the Akagi and Kaga initially, and the cruisers of the Aoba/Furutaka classes, as well as the Myôkô class.
These 17.6 tons (17.9 mt) had a rate of fire of 2 initially (Kaga) and up to 3-5 in the later version. Approximate Barrel Life was 300 rounds and the ships had about 120 rounds in store for each. Range at 45° was 30,620 yards (28,000 m). More

50 caliber 3rd Year Type 20 cm Gun 2 GÔ (No. 2)

The “modern” 203 mm (8 inches) caliber, found on the Takao class. They tried to correct large dispersion patterns, and were fitted on the Takao and Tone classes as well as the rearmed Furutaka, Aoba, Myôkô and Mogami classes as well as the unbuilt Ibuki class. Performances: 3-4 rounds per minute, range 27,340 yards (25,000 m)/30°, 1,247 fps (380 mps) terminal velocity, able to defeat 2.9″ (74 mm) armor at 30,000 yards. More

60 Caliber 3rd Year Type 15.5 cm Gun

When the Mogami class were rearmed with lighter guns following the Londong treaty signature in 1930, these were the new guns adopted. They swap back onto the 20 cm guns again after reconstruction 1939-41. Their former mounts were reused on the Yamato class battleships and light cruiser IJN Ôyodo (which had two such turrets). They had a slow rate of fire and limited elevation and were useless as dual-purpose but stayed accurate in their anti-ship role. Their theoritical rpm was 7, but in reality only 5-6 rounds per minute was achieved. Range 27,340 yards (25,000 m)/55°. They could defeat 4.2″ (108 mm) of armour at 16,400 yards (15,000 m). For the Kuma/Nagara/Sendai classes, see the WWI section.

DP/AA Guns

127 mm (5 in) dual purposes on IJN Chitose before conversion

As standard, these ships were equipped with the following:
45 caliber 10th Year Type 12 cm: cruisers built in the 1920s and early 1930s.
40 caliber Type 89 12.7 cm Gun: Standard DP gun on cruisers in the 1930s. The great standard, 14 rpm/30,840 feet (9,400 m) ceiling. More
3″/40 (7.62 cm) 3rd Year Type: Furutaka/Aoba
25 mm Type 96: The ubiquitous main AA gun of the IJN, present virtually on all ships in single or triple mounts , replacing often the 13.2 mm Type 93 heavy machine gun .

Of course this point would be gravely incomplete without mentioning their fabled Type 93 Torpedo, the famous “long lance”. Although not as famous as the German 88mm, British 17-pdr or the Bofors 40mm, this “secret weapon” was certainly the best asset of the IJN and best torpedo of WW2. Given its results in several “close-quarter” battles notably in the Solomons, and the poor performances of the US Mark 14 conversely, explains partly the crippling losses of the USN until late 1942.
The Type 93 was designed from 1928 by Rear Admiral Kaneji Kishimoto, and Captain Toshihide Asakuma and was accepted for production in 1932.
No nation at the time indeed had a torpedo that carried a larger payload (1018 kgs) to 43,700 yards (40,000 m) at 36-38 knots or going to 21,900 yards (20,000 m) at 50 knots.

Other Torpedoes

61 cm (24″) Type 8 No. 2 (1920): On the Kuma/Nagara/Sendai classes
61 cm (24″) Type 90 (1930): Interwar heavy cruisers, Aoba, Furutaka, Nachi/Takao before replacement by the Type 93.
61 cm (24″) Type 93 (1933): Model 1, Mod 1, Mod 2 and Mod 3, all cruisers in 1941, including the unbuilt Ibuki class.
61 cm (24″) F3: First Experimental Turbine powered torpedo, 17,500 rpm geared down to 1,650 rpm at the propellers but capricious and not adopted.

Powerplants and performances

Differences between a Yarrow and Kampon boilers drum arrangement

The oldest cruisers in service in 1941, mainly converted as minelayer/training vessels from the late 1890s or 1900s still around indeed had quite antiquate machinery limiting their top speed to 18-20 knots making them unable to take part in any fleet exercize. The Asama-Idzumo (Armstrong), Yakumo (Vulcan), Adzumo (Loire Yards) had different powerplants but all were VTE, coal-burning. It seems none received any engine upgrades. The scouts of the Chikuma class (1911), still around in 1940-41, had Parsons/Curtis steam turbines and Kampon boilers and mixed coal/oil burning.

Next, were the active ships of the Tenryu class (1918): First with Brown-Curtiss turbines to achieve 33 knots. This became the new IJN speed standard for the fleet. After all they were destroyer leaders. The first cruisers with national turbines were the Kuma class (1919) which had Gihon steam turbines for 36 knots, and moslty oil-burning. This was repeated on the Nagara class (1921) and even on the Sendai class (1925), which all shared the same 90,000 bhp powerplant. They typically carried 2/3 oil and 1/3 Coal.
The transition to oil-only was not yet achieved on IJN Yubari, which was revolutionary at other titles. She had three shafts, not four as usual, same generation, but more compact geared turbines to reach 35.5 kts. The Furutaka and Aoba as built also carried a mix of Oil/coal and were capable of 34.5 kts (less after modernization).

Kampon Ro-Go and Type B boilers

However innovation came from the next heavy cruiser generation of the Nachi and Takao class: They had still four Gihon geared turbines, but coupled with 12 Kampon new generation boilers, burning only oil. With 130,000 shp they reclaimed the speed lost at 35.5 kts, while the Mogami class had a new generation of superheated boilers, and with just ten, achieved 152,000 shp for a record 37 kts. They were the fastest cruisers in Asia. That is, before their reconstruction. The added tonnage made them closer to 35 kts at best in early 1942.
The Tone class (1937) still managed the same output with eight boilers, but kept at 35 kts as the fleet standard.

Exhaust and boilers arrangement on a Takao class cruiser

The small Ibuki class were an exception, designed as training/HQ ships. They mixed diesels and turbines for extra range (which was exceptional) and with just three boilers, only achieved 8000 hp, for 18 kts, escort speed. The light cruisers of the Agano class counted on the same powerplant as the larger cruisers, but with just six boilers in a compact arrangement. These slender vessels achieved 35 kts, sufficient for their task. The Oyodo, single in her class, had about the same arrangement but were a bit more powerful at 110 instead of 100,000 shp. They all had four drive shafts and three-bladed bronze screw propellers. It must be said that interwar aicraft carriers copied cruisers powerplants to achieve speed in excess of 36 kts (Notably Soryu/Hiryu), making them the world’s fastest aircraft carriers (The lexington class came close at 33 kts).

The gargantuan Kampon Mk.25 mod 2 diesels in 1944

As for the Ibuki class, she was not innovative in particular: She started as a repeat of the Mogami class, but when decision was made for a conversion, the first and single ship of the class modified had her powerplant halved to make room for extra aircraft, ammunition or avgas tanks: She ended with two shafts and geared turbines fed by just four Kampon boilers for 72,000 shp and 29 kts (as planned).
The heavyweights in this serie were also also unbuilt “B64” type cruisers: These were more capital ships than “cruisers” and were capable of 160,000 shp for 33 kts.


Takao class midship armour scheme. It shows a relatively common trend at the time, with an inverted external sloped belt, central turtleback type section, well compartimented ASW compartimentation with bulges also used for extra stability, divided into crush half-tubes. They had no conning tower, and only the ammunition magazines were the best protected parts of the ships, with 100 mm thick boxes, deep inside the ship, counting on the energy dispersion effect of the decks above. Indeed, cruiser’s ammunition explosions has been exceedingly rare, but cases of spare torpedoes detonating was not unusual.

It varied from ship to ship, and types. We are going to start with active cruisers in WW2, the Tenryu class and 1919 programme. As scouts, these were lightly protected, intended to only fight other destroyers. It was limited to a 2-in belt (51 mm) and 1-in deck (25 mm), creating a small “immune zone” on a very limited distance, representing 1/3 of the ship and centered around the machinery spaces. In comparison even the previous Chikuma class were better protected. However these new cruisers were capable of 33 knots, same as destroyers, making them more difficult to hit anyway.
The trend was continued on with the next Kuma, Nagara and Sendai which had about the same scheme. “Immune” area around the machinery space, but thicker at 2-1/2 inches (63 mm) and 1-1/2 inches (32 mm) respectively for the horizontal and vertical protections. The Sendai class (1925) were about the same, 2.5 and 1.1 inches respectively.

The experimental Yubari (1923) designed by Hiraga, experimented a new kind of structural protection, and it was installed internally and sloped unlike previous cruisers. And it contributed at the same time to the longitudinal strenght of the hull, a way to used all available steel plating count in a dual role. This way, this made the structure lighter overall. But fugures were still limited: 2.3 in for the internal belt, shorter than the outermost barbettes, 1-in (25 mm) both for the armored deck and gunhouses.
For the early heavy cruisers of the Furutuaka-Aoba class, the same recipe was applied, but the belt reached 3.4 in (86mm) -even 3 inches on Aoba- and the deck 1.4 in (35mm), the gunhouses (turrets) stayed at 1-in. If they were intended to combat other 8-in armed cruisers, this was ludicrously light.

For the Nachi class, at least the belt was augmented to 3.9-in (100 mm) but the deck armor remained the same, as the turrets, but at least the main barbettes were augmented to 3-in (76 mm). The next Takao class had the same scheme, but this time localized areas were better protected, as the ammunition magazines, boxed into 4.9 in (120 mm) compounds. The bridge was absolutely massive and abl to “absorb” extra punishment. As for the Mogami class, they followed the general trend of all Washington cruisers, and improved their protection a bit. The belt remained the same, they had the same boxes magazines, but a better, layered deck protection ranging from 1.4 to 2.4 in (35-60 mm).
The Tone class had the same scheme, but with 1.2 to 2.5 in for the deck protection. Protection of the turrets was still paper thin (1-in/25 mm). The next Ibuki class was a repeat of the Tone class scheme.
It must be said a few authors pretended that Japanese steel was naturally of general better quality, given perhaps the local ore, adding to the protection, in addition to Hiraga’s construction “wizardry”. It’s not the case. All sorts of stell qualities were recycled if possible, and the reputation of Japanese swords was not due to the material use, but the skills of the master smiths. The fundry tech in Japanese was borrowed from western techniques, mainly those of Britain originally, and through their purchases, Japan tested Krupp and Harvey armor as well. They did not came with a revolutionary “special process” for hardened steel of their own, at least one that is know of.


Japan came to radars a bit later than the allies. It is also often said that their optics were of superior quality and by clar weather, or even by night the “eyeball Mark I” was still the best long range detection asset of the IJN, this was especially true in the Solomons. Optical detection used to out-range US radar detection, especially because of the surrounding relief. The main types were the Ta-Se 1 Anti-Surface Radar and Ta-Se 2 Anti-Surface Radar. Hiwever the Japanese developed 30 different types of sets and had 7256+ sets of all types built. Late and far less effective than that of the Allies, they still were fitted on all surviving cruisers from 1943 onwards. Some cruisers had their mainmast rebuilt as derricks to support large aerial warning sets.
More on the topic.

IJN Cruisers in action in WW2

IJN Nachi in sea trials
Cruisers were classed in three categories, which defined their roles, depending on their capabilities:
-The pre-WWI cruisers still active (mostly armoured cruisers) were reclassed as training ships or minelayers and used as such.
-The 1919 program cruisers (Tenryu, Kuma, Nagara, Sendai) were considered obsolescent in 1941 and used generally (there were exceptions) as assault forces escorts, also providing fire support. In some rare cases they were used as destroyer leaders, but not ion the fleet screening role. Their role was retaken by the post-1942 Agano class, but by 1944 they were used to replace loss in standard fleet operations. IJN Oyodo was never used as intended (leading submarine attacks), and ended as fleet HQ ship. The Katori class were used as escorts for convoys and assault forces, and floating HQs, so about the same as above.
-The “fleet cruisers” (Furutaka, Aoba, Nachi, Takao, Mogami and Tone classes) were the real deal, used as part of combined fleets with battleships and carriers, or independently with destroyers, notably for cruiser forces interception (like ABDA in the west indies, or Solomons fleet moves). By default of battleships, the US used their cruisers, and the IJN answered the same, keeping their capital ship for more important operations. As befitting of cruisers, they could act independently with the escort of a few destroyers.

As said above about radars, the IJN developed the reputation of markmanship’s gunners. They also had generally good gunnery direction. There were excellent optics in general and they tended to detect their foes earlier. Not only they were able to place salvoes on target consistently but also at longer ranges.

Onboard air groups and hybrid cruisers

IJN Oyodo, a standard hybrid cruiser intended to lead submersible attack groups on long range missions, equipped with the mediocre Aichi E 16 A Zuiun “Paul”.

The other factor was long range reconnaissance, well above the range of any radar. These cruisers had generous seaplane provisions, and in fact tactically were often used as “eyes” of the fleet. When integrated into combined battle formations, they screened the capital ships and sent their seaplanes before any engagement to sport and report the enemy formations. This was crucial for the “first air strike”. Let’s take two models to have a clearer view of this:

Kawanishi E7K2 “Alf”. This long range reconnaissance model was standard on all cruisers in 1941 (here IJN Abukuma).

Nakajima E8N2, IJN Nagato, 1941.

Note the different in size. This was also traduced in range, which nearly was double on the Cruiser’s models. The contemporary E8N was more an artillery spotting model.
They were replaced by the Aichi E13A and Mitsubishi F1M respectively. 1919 program cruisers only had an axial catapult and single model, but later fleet cruisers had two or even three of these, a small hangar, two catapults and a deck trackway to store and dispatch non-mounted models. Usually there were two mounted on their catapults and a third, wings folded, kept in reserve. Even the small Agano had two. Some cruisers were even transformer to carry more: The Tone carried six as the Oyodo, and the Mogami was completely rebuilt also as an hybrid cruiser. This also concerned battleships, with the Ise class also rebuilt that way in WW2.
They played an important role in several engagements, reporting enemy fleets, but never really filled all the hopes placed in them. The case of oyodo is interesting by the way and Mogami also carried models intended to carry torpedoes and bombs.

Probably the best “observation/fighter” aboard IJN cruisers was the F1M “Pete”.
It was also not unusual for cruiser’s floatplanes to fill the role of carrier aviation, downing enemy aircraft (it was often the case over China) or supporting troops during assaults. Probably the best floatpolane “fighter” actually carried by cruisers was the Mitsubishi F1M “Pete”, which was high performances despite it’s biplane configuration. In fact the theoretically better A6M2-N “Rufe” was never adopted for cruiser service, kept for the defence of isolated island garrisons.

Cruiser Doctrine since 1894

One Famous cruiser tactic was the night combat:
A whole doctrine was developed around it, maximizing the cruiser’s heavy torpedo armament. Some early principles were also laid down by Baron Vice Admiral Tsuboi Kozo. A Rear Admiral in 1894, he led a special force of four extremely modern cruisers, called the “Flying Squadron” of the Imperial Japanese Navy during the 1st Sino-Japanese war and at the Battle of Yalu. He was not content to just act as a scouting force for the main fleet but took his squadron on long distance “reconnaissance-in-force” missions. Instead of dispatching his four cruisers separately for commerce warfare, he kept them together to put under heavy fire any encountered hostile unit with Guns and torpedoes. He wanted this unit to move quickly and striking key locations in rapid succession with surprise and strength. This unit became famous and had a legacy teached in the Etajima naval academy all the way to WW2. In between onboard aviation appeared, and later torpedoes were developed to a further level, enabling new capabilities.
The question of artillery was also an issue: Kubo’s squadron only had slow-firing 8-inch guns, fine against armoured cruiser but usuless against destroyers at short range. The concept of fleet light cruiser was developed in the IJN after the Second London Naval Treaty.

These tactics centered around a powerful cruiser force was put to good use at the Battle of Sunda Strait, Java Sea and Savo Island.
Nevertheless, the Japanese fleet devised two general types of surface warships (neither capital nor carriers), mainly torpedo carriers with secondary gun batteries, and mainly gun carriers with secondary torpedo batteries. Destroyers represented the first category, and heavy cruisers the second.
There was still the need of a combo between heavy cruisers and large light cruisers, as the Mogamis and Tones were originally meant to be, before reconversion. Combining long range gunnery with rapid fire against enemy destroyers would indeed have made these combinations more effective.

Organization and Use

From December 1941, the IJN mustered its eighteen heavy cruisers and four supporting fast battleships (Kongo class) actively used for the conquest, with destroyers supporting screens. They were dispatched to operate over half the Pacific, organized into five cruiser divisions (which were classes) and five supporting forces. Two of these five supporting forces had a pair of fast battleships each. These forces could have both land-based or carrier air based support (such as the forces which claimed Force Z), sparing the IJN a potentially challenging surface combat.

1942 divisions (“squadrons”):

ATAGO class (CruDiv 4): Atago (F), Takao, Maya, Chokai
NACHI class (CruDiv 5): Nachi (F), Haguro, Myoko (F), Ashigara
AOBA class (CruDiv 6): Aoba (F), Kinugasa, Furataka, Kako
MOGAMI class (CruDiv 7): Mogami, Mikuma, Kuman (F), Suzuya
TONE class (CruDiv 8): Tone (F), Chikuma
CruDiv 16 (formed 1943): Aoba (F), Ashigara, and two light carriers
CruDiv 21 (former 1942): Nachi (F), Maya/Ashigara, two light carriers
(*F: Flagship)
They were assisted by destroyer squadons with various strenghts, sometimes as low as two ships.

The Indirect Escort of Convoys from March 1942 on counted on three heavy cruiser divisions (12 ships in all) screening landings over the Pacificn with CruDiv 7 taking on Malaya, Sumatra, and western Java, CruDiv 5 the Philippines, Celebes, and eastern Java, CruDiv 6 Guam, Wake, and Rabaul. The distant cover meant the transports did not even saw them, but closer, older 1919 program cruisers as direct protectors. This never led to troubles as the allied response was so weak at first. In addition this organization meant the heavy cruisers were not stuck to close protection and could be detached of need be:
This was case at the Battle of the Java Sea (February 27, 1942) when Nachi and Haguro until then attached to the support of 41 transports, went sent to fend off the ABDA Allied cruiser force. They were repulse three times over seven hours. Long-range daylight battle was not in their favour however with only six hits scored after an hour, but victory was secured in a night action at 8000 yards with torpedoes (also fired from destroyers) working their magic. The Dutch navy was equally unaware of their range, as their allied counterparts.
However this indirect support was not always successful: It failed in Makassar Straits as the supporting Japanese cruisers were too far north to inetrvene, and when USS Houston and HMAS Perth ran into a fleet of transports while under hot pursuit (by the cover cruisers) off Java, they sank four of them. Mogami and Mikuma were again not present.

In the attempted capture of Port Moresby in May 1942 the four Aobas (CruDiv 6) were reployed in screening the support carrier force, while CruDivs 5, 6, and 7 were screening the invasion force proper, and CruDivs 4 and 8 were in close protection of the Kido Butai. The 8th screened with the fast battleships Hiei and Kirishima. They were a kind of “supporting force of the supporting force”. The Kido Butai had de facto the most powerful screen force at the time, four fast battleships and six heavy cruisers. These cruisers provided intel, via their seaplanes, notably Tone and Chikuma. This early phase saw only IJN Myoko damaged, at Davao by a B17 bomb on January 4.

Haguro in the raid of Rabaul, November 1942

A fast bombardment force was later built around Cruiser Division 7. CruDiv 8 at Midway failed to prevent the destruction of the four carriers. Tone’s floatplane sighted USS Yorktown, allowing the IJN some retribution at last. CruDiv 7 failed as the mission was aborted following the disater, Mogami rammed Mikuma after a sub sighting and later Mikuma was sunk and Mogarni severely damaged by US Carrier planes.

During the Solomons campaign these heavy cruisers were used for antishipping raids, and shore bombardments, notably at Guadalcanal, their use evolving along the situation on the ground. The night raid on 8-9 August which fed the future “ironbottom sound” was by far the mpst successful. They approached undetected due to the surrounding volcanic peaks and hills, defeating the US primitive radars, fired torpedoes and finished the job with heavy guns at close range, acheving complete surprise. The US lost four cruisers that night, including three New Oerlans class in one go. The remainder of this one-year gruelling campaign the Japanese would try to replicate that success.

In the next daylight two carrier battles of Eastern Solomons and Santa Cruz, cruisers fare with little success, due mostly to their inadequate AA. But again, reconnaissance planes of those were decisive: On August 25, one of Chikuma’s seaplanes sighted the USS task force (USS Saratoga and Enterprise). They also fought not decisively in subsequent actions and were limited afterwards to bombardment runs of the “Tokyo Express”, not carrying supplies or troops themselves, as too precious.
After the Battle for Guadalcanal these cruisers were pulled back and retired in the central Pacific, notably to operate from Truk.

Nachi, Maya, Aoba, and Ashigara were more active, with the first two part of the 21st Cruiser Squadron with Tama and Kiso, seeing action in the Aleutians (5th fleet).
The last two were sent to the 16th Squadron with the light cruisers Oi and Kinu in the South Pacific. In both cases they acted as distant support, the two older cruisers being in close protection of the troopships.

Nachi at the Battle of Manila Bay, 5 November 1944

At the Komandorski Islands Nachi and Maya perfrormed poorly against an inferior force. They landed only 0.33% hits out of 1,800 main rounds fired on Salt Lake City and all their torpedoes missed. Myoko and Haguro fared little better at the Empress Augusta Bay on November 1, 1943: Without effective radar they lost 30 min. firing poorly, and were damaged in between. Despite the oppostion only had 6-in guns, they did not excelled in markmanship to say the least, and retiring with damage after achieving little.

As for the central pacific, a major raid at Truk damaged Atago, Takao, Kutnano, Tone, Mogami, and Maya, while Suzuya and Chikuma escaped unharmed. At Saipan they were mostly absent, and in the Philippines this was mostly an air war, and again, they could do little with their inadequate AA to protect the fleet.

IJN Takao “rotting”, camouflaged in Singapore, as captured by British forces

The last occasion of a naval action was at the battle of Leyte in October 1944: But eight Japanese heavy cruisers were lost in the battle, the bulk of the fleet. After that Tone and Aoba were sent in Kure for repairs and never left home waters before their execution in the summer of 1945, whereas Myoko, Takao, and Haguro were sent permanently to Singapore, Ashigara in Indochina. This was pretty much game over for the IJN Cruisers at this juncture.

Night Combat

< Raizo Tanaka, a master cruiser tactician. There is a long legacy to the concept.
The Japanese navy specialized in the early interwar in a new kind of “night torpedo action” bringing their new heavy cruisers into very close range, putting to good use the range of their torpedoes, something completely overlooked by the USN. The Battle of Savo island was a textbook example of this, but it was not the only one.
However a usual, fate has these plans not working on the long run. The US had better radars ultimately and used their submarines in very efficient ways to detect enemy forces. The Japanese staff had to decide ultimately to use their “tokyo Express”, based around a core of cruisers, to resupply by night their beleaguered troops on Guadalcanal. This led to several night actions with various fortunes.

Too many limitations

The IJN, even after eliminating the bulk of the USN capital fleet at Pearl Harbor, continued to consider heavy cruisers as the backbone of their operations, with fast battleships ready to support them a la Hipper (usually the Kongo class specifically), but they were still too few and precious to be committed each time. To put it mildly heavy cruiser squadrons put most of the fighting, while the Japanese battleline accumulated barnacles in the Inland Sea, notably “Hotel Yamato”, despite being the most formidable asset until the USN reclaimed total air dominance over the Pacific. This was compounded with the failure of the IJN to recoignise the danger of US Submersibles tactics early enough. They too, preyed on these hard-pressed cruisers.

However in the end, the failure to consider cruisers with rapid-firing medium guns rather than sticking on armour-piercing heavier guns -the after effect of a long obsession with circumventing treaty limits- eventually produced a fatal gap in tactical firepower capabilities. With their generally good heavy cruisers but mediocre light cruisers, the fleet lacked intermediate, modern large or medium light cruisers that can fill gaps, comparable to the USN Brooklyns/Atlanta in 1942.

The IJN industry was nowhere near the capability of the US industry to provide these, as shown by the small number of Agano built (4 of 24 planned initially), Oyodo (One on 12 planned) or Ibuki (none, converted to CVL). Changing priorities converged after the disater of Pearl Harbor to aircraft carriers and smaller escorts. Or even “super destroyers” to fill that gap. IJN’s Agano class were still a prewar project completed in wartime, IJN Oyodo being the real only Japanese wartime cruiser (launched 1943) taking some lessons of these deficiencies, but making the choice of an hybrid configuration. It was large enough to have been given three or even four tripl turrets with 6-in guns.

To compare at the same time, the USN laid down more than 65 keels for light cruisers (Cleveland and Atlanta class) and 30 keels for heavy cruisers, completing most of them, the Royal Navy itself commissioning also many new cruisers during that time.
This lack of resources meant efforts were concentrated on aircraft carriers, escorts, “secrets weapons” such as the Kaiten submarines, or Shinyo Motor Boats, the Yamato and Mushashi absorbing most of available the resources in 1941-42. Would more cruisers had changed the nature of the fight in 1942-43 ? Not really, as air power was the dominant factor, but until the Japanese retired from Guadalcanal, operations were mostly led by Cruisers, especially by night, and they proved very efficient.

USNI Japan’s Heavy Cruisers in the War (1950)
US Postwar assessement of IJA night combat
See also the tabular record of movements of the cruisers

Vintage IJN Cruisers in WW2

Tsushima (1902)

Hulked 1930. Sunk 1944. Also hulked, IJN Adzuma, but in 1941. Survived the war into 1946 and BU. On 1st September 1921, IJN Tsushima was re-designated a “2nd class coastal defense vessel”. In 1922 seh received six modern 15.2 cm and eight 12-pdr (3 in) guns. Later in the 1920s she was given a single 12-pdr AA gun. She became the main patrol vessel on the Yangtze River and Kichisaburō Nomura’s flagship, at the head of a gunboat fleet.
IJN sushima was partially disarmed in 1930 and became back home a training ship, struck in 1936. She became “training hulk Hai Kan No. 10”, annchored at Yokosuka Naval District, until 1 April 1939. She ended her life as a target ship off Miura (Kanagawa) by torpedoes in 1944.
As for Niitaka, from September to July 1920, she covered landings of the IJA in Petropavlovsk as part of the anti-Bosheviks Siberian Intervention and as fishery protection vessels for Japanese trawlers along the Kamchatka Peninsula. By May 1921 she was patrolling southern China and down to the Netherlands East Indies, and South China Sea. From September 1921, she became a “2nd class coastal defense vessel”. On 26 August 1922, she was based on the southern coast of the Kamchatka Peninsula, sending a landing party of 15 led by Lieutenant Shigetada Gunji ashore, looking for presence of Belsheviks there. Ironicall they became survivors as the while crew disappeared when the ship was caught by a sudden typhoon, with gale winds drossing her onto rocks. She was overturned. A salvage team went there in 1923 to examine the wreck and see if it was recoverable. But it was not to be and the wreck was finished off with explosives, and the metal taken away. She was stricken on 1 April 1924.

Training Cruiser IJN Asama (1898)

IJN Asama towed in Sydney, 1930s
After the war Asama was used as navigation training ship, performinge long range cruisers for cadet officers. On 21 August 1920, she visited South America and Polynesia but by late 1921 she was re-designated a 1st class coast defense ship. In 1922, her main deck guns were removed as six 6-in, four 12-pdr guns, QF 2.5-pdr guns and casemates plated over. A single 8 cm/40 3rd Year Type AA gun was added however.
From 26 June 1922, her training cruises brought her to Australia, Southeast Asia, and Mediterranean; but she ran aground on the night of 13 October 1935 NNW of Kurushima Strait, Inland Sea. Rngineers estimated that she was difficult to repair. Towed to Kure she was provisionally repaired, and assigned the Kure naval Corps as a stationary training ship from 5 July 1938.

Asama as a barrack ships in 1946. She was BU the next year.
She was reclassified as a training ship in July 1942 and was later converted as a gunnery TS at Shimonoseki, keeping a few 80 mm/40 (78 in) 3rd Year Type AA guns in 1944. But she was eventually stricken on 30 November 1945, scrapped at the Innoshima shipyard (Hitachi Zosen) after the war, from 15 August 1946.

Minelaying Cruiser IJN Tokiwa (converted 1928)

IJN Tokiwa in 1945
Tokiwa, a former Asama class armoured cruiser built in Britain (launched 1898), was reassigned to the Training Squadron on 10 August 1918 and prepared a training cruise with Azuma from 1 March 1919 for South Asia-Australia. From 24 November she stopped at Singapore, visited Southeast Asia, crossed the Indian Ocean, Suez Canal and entered the Mediterranean Sea, back home by 20 May 1920 and left the Training Squadron in June, reclassed as 1st class coast-defense ship and taking in hands at Sasebo on 30 September 1922, for conversion into a minelayer:
She was modified to carry To accommodate 200–300 mines depending of the type:
-Rear 8-inch gun turret, six 6-inch guns (main deck) removed.
-Rear guns were removed and two 12-pdr retained
-Two 8 cm/40 3rd Year Type anti-aircraft guns added.
The process ended by March 1924 but she suffered whilke in service an accidental explosion in Saiki Bay (1 August 1927) when mines were disarmed. One detonated, fllowed by others and 35 were killed, 65 wounded. Tokiwa was repaired and went to the reserve fleet. From January 1932 she joined the 1st Fleet, until May 1933. She served in China. From November 1937 she was druyocked and gutted, with eight new Kampon boilers, with a speed down to 16 knots (30 km/h; 18 mph), torpedo tubes removed. The freed space enabled to carry 500 extra mines. She was reassigned to the 4th Fleet on 15 November 1939, then 18th Division, 19th Division in 1943 (Rear Admiral Kiyohide Shima) with the other minelayer IJN Okinoshima. In 1940, she received two single 40-mm (1.6 in) guns, 20 Hotchkiss 25-mm Type 96 light AA guns (twin-guns).
On 9-10 December 1941, IJN Tokiwa and other minelayers from the 19th Division escorted two troop transports for Makin and Tarawa. By January 1942, Tokiwa took part in Operation R to Rabaul and Kavieng andlater Kwajalein. February 1942 saw her attacked by planes from USS Enterprise, she was later repaired in Sasebo and was back to Truk on 14 July 1942. On the 19th she joined the assault Makin squadron tasked to reoccupy the Atoll after the USS Raid.

On 1 May 1943, she was part of the Ōminato Guard District. She left Truk on 26 May to escort a convoy to Yokosuka ambushed but missed by USS Salmon (SS-182) in June. She was reassigned to the 18th Escort Squadron, 7th Fleet, on 20 January 1944. She was reamed with ten single 25 mm Type 96 AA guns and 80 depth charges as well as a Type 3-1, Mod 3 and Type 2-2, Mod 1 radars. She layed a large minefield off Okinawa the same month, and off Yakushima in February 1945.

However on 14 April 1945 (78 miles off Hesaki- Kyūshū) she hit a mine, but damage was moderate. USAAF B-29 Superfortress bombers laid mines and she hit another one on 3 June 1945. Caught by TF 38 US aviation while off Ōminato, Mutsu Bay (northern Japan) on 9 August 1945 she took several near-misses and at least a direct hit. Her captain decided to have her beached to avoid sinking. On 30 November 1945 she was stricken and her wreck, partially underwater, was relfoated and towed for demolition in Hakodate, BU in August–October 1947.

Coast Defence ship IJN Yakumo (1899)

The single German (Vulcan-built) armoured cruiser (launched 1899) was still active in 1918. On 1 September 1921, she became a “1st class coast-defense ship” used for training, as her sisters making long oceanic navigation trips with academy cadets, making 13 of these cruises in the interwar, visiting all continents over time. She even made a circumnavigation of the globe (August 1921-April 1922) with IJN Izumo, with distinguished hosts such as Princes Kuni Asaakira and Kachō Hirotada.
In 1924, her armament was modified: She her most her 12-pdr guns and all QF 2.5-pdr, three TTs removed, but eight single 8 cm/40 3rd Year Type AA guns added. In 1927, she was drydocked for her boilers to be replaced by six modern coal/oil-burning Yarrow boilers from the rebuilt IJN Haruna. He new output was 7,000 ihp (5,200 kW) for 16 knots. She carried 1,210 metric tons of coal and 306 metric tons of oil.

Yakumo off Vancouver, 1933

With Izumo she landed IJN Marines in Tsingtao by 1932 to quell a riot of Japanese residents and in 1933 she became a training ship. From 6 November 1936 she suffered an accidental explosion while underway between Saipan and Truk. This was in the front ammunition magazine. 4 were killed, but it was quickly flooded. Two weeks later she was repaired. By December 1936 she had a new captain, Matome Ugaki, departing in 1937 for IJN Hyūga. She made new cruises in 1937 and 1939, the last ending on 20 November 1939.

From early 1942, IJN Yakumo was fully reactivated as “1st class cruiser”, on 1 July 1942. Her main guns were by four 12.7 cm (5.0 in) standard Type 89 DP guns in two twin mounts in place of her former 8-in turrets. She also receibed extra 25 mm in triple and single mounts. She was based in the Seto Inland Sea for training until stricken on 1st October 1945. She started repatriation trips in December, notably from Taiwan and mainland China. Her last ended by June 1946, with 9,010 onboard. She was sold and BU at Maizuru (Hitachi Shipbuilding) by July 1946.

Izumo class Coast Defence ships (1899)

Izumo 1932
The lead ship of the Izumo class, veteran of the Russo-Japanese war participated in the 1919 Naval Review in honor of Emperor Taishō. “1st class coast-defense ship” from September 1921 she also was a oceanic navigation training ship for the Academy, making six voyages in the 1920s-1930s and a circumnavigation from August 1921 to April 1922 with Yakumo. On 7 February 1925 she collided with a tugboat at night.
In 1924 she had a first refit: 12-pdr guns, QF 2.5-pdr guns, TTs removed later in 1930 and single 8 cm/40 3rd Year AA gun added. Her final armament was just four 12-pdr (3-in/76mm). In 1935 she was drydocked, six Kampon water-tube boilers (7,000 ihp/16 knots) replacing her former large powerplant. This freed space for more bunkerage and extra cadet accomodations/instructor spaces. She had 1,428 metric tons of coal, 329 of fuel oil, and displaced 10,864 metric tons.
On 2 February 1932, she intervened after the first Shanghai Incident, as flagship, 3rd Fleet (Admiral Kichisaburō Nomura). In 1934 she was refitted in Sasebo, receiving a floatplane.
As the Second Sino-Japanese War started by July 1937 she was attacked on 14 August by the Chinese Air Force in the Battle of Shanghai. Two bombs landed among spectators. Izumo’s Nakajima E4N floatplane and another from Sendai claimed to have shot down one Curtiss Hawk biplane and a Northrop Gamma. Her E4N claimed another Hawk afterwards. She was attacked by a Chinese torpedo boat, but torpedoes missed. The TB ws promptyy destroyed. Next, she provided naval gunfire during the battle. Chinese aircraft attacks went on but she had no hit to report, only strafing attacks.
Izumo was still there by 8 December 1941. She captured the USS Wake and gunned, sinsked the HMS Peterel. On 31 December however she hit a mine in Lingayen Gulf while taking part in the Philippines Campaign. Towed to Hong Kong by February 1942 she was repaired, and re-classified as a “1st-class cruiser” by July. By late 1943 she was a training ship in Kure and by 19 March 1945, while off Etajima she was attacked by airplane but only had light damage. He antiquated 8-inch guns were at last replaced by twi twin 12.7 cm (5.0 in) Type 89 DP and her last 6-in guns removed. She received 25 mm Type 96 AA guns (2×3, 2×2, 4×1 mounts) and 2×1 13.2 mm Hotchkiss HMGs. She hit an aerial mine on 9 April off Hiroshima and was near-missed by 28 July 1945. These caused flooding extensive enough to turnover and capsize slowly for most of the crew to survive. Stricken on 20 November she was scrapped in 1947 at Harima Dock. More (TroM)

Training Cruiser IJN Kasuga (1902)

Part of the Nisshin class purchased to Italy in 1905, this veteran of the Russo-Japanse war and WWI arrived in Portland, Maine for the state centennial celebration on 3 July 1920, visited New York City and Annapolis, Cristobal (Panama) and San Francisco. She carried soldiers and supplies to Siberia in 1922 (Siberian Intervention) under command of Mitsumasa Yonai (future Prime Minister of Japan) and on 15 June 1926 rescued off Japan the crew of the freighter SS City of Naples.
From 1927 she was rerated as a training vessel for navigators and engineers and by July 1928 rescued the crew of airship N3 during fleet maneuvers. By January–February 1934 she carried 40 scientists to Truk for a solar eclipse. Hulked and disarmed by July 1942 she became floating barracks, capsizing at her mooring at Yokosuka on 18 July 1945 after near-misses of an air raid. She was salvaged in August 1948, BU at the Uraga Dock Company. No photo exist to my knowledge of her during the war.

Hirado(Chikuma) class (1911)

Hirado, Yahagi

Hirado in 1912, note the clipper bow. She apparently never changed appearance in the interwar.
The Chikuma class were two scout cruisers of the IJN, the first of their kind. Fast and moden there were comprehensible restrain to scrap her after the Washington treaty. Her sister Chikuma was sunk as a target ship, 1935, while Yahagi was discarded on 1 April 1940. As for the only one active in 1941, IJN Hirado was assigned to patrol off the east coast of Russia for supply and troop convoys to Siberia, taking her share of service against the Bolshevik Red Army. Her captainw as soon the future Fleet Admiral Osami Nagano (1919-1920) and then Captain Zengo Yoshida until December 1924.
She was tasked to guard the southern approaches to Japan, stopping in Manila and Macau. From 1932 she was reassigned to the northern coast of China and after the Manchurian Incident, based in the Ryojun Guard District (Kwantung Leased Territory). She was plagued all along by engine problems.
Placed in reserve vessel in 1933 she became a training ship, officially stricken on 1 April 1940 but used as the barrack ship Hai Kan No.11 at Etajima Naval Academy and Kure. Towed to Iwasaki in December 1943 she was scrapped postwar, by January-April 1947.

Tenryu class (1918)

Scout Cruisers Tenryu, Tatsuta

If the great cruisers of the class Kuma, Nagara and Sendai are better known, they constitute an evolution of these precursors, built during the great war. Indeed, the Tenryu and the Tatsuta were defined by the Admiralty in 1916 who wanted a kind of “super-destroyer” based on the British design of the Arethusa and “C”. Under the name of project 33, they were laid down in 1917 two months apart at the Yokosuka and Sasebo shipyards. They had been defined as squadron leaders capable of 33 knots. They also received the new 140mm guns fitted to the two Ise-class battleships. They were also the first to benefit from triple banks of torpedo tubes.

During their long active career (launched in 1918 and completed in 1919), they received a sturdier tripod foremast. Originally, their DCA was provided by a single 78 mm mount, replaced in 1941, after being supported by two 13.2 mm machine guns in 1939, by 5 double 25 mm mounts. The Tatsuta however retained its 78mm on the rear shelf. During the war, they mainly performed escorts. The Tenryu was sunk on December 18, 1942 by an American submersible, the USS Albacore. The Tatsuta survived her only until April 1944, to be torpedoed and sunk in turn by another submersible, the USS Sandlance.


Displacement: 3,948 t. standard -4,350 t. Full Load
Dimensions: 142.9 m long, 12.3 m wide, 4 m draft
Propulsion: 3 shafts Kampon SG turbines, 10 mixed boilers, 51,000 hp= 33 kts
Armor protection: From 51 (belt) to 25 mm (Main Deck)
Armament: 4×1 140 mm, 1x 78 mm, 8x 25 mm AA, 2x 13.2mm AA, 2×3 610mm TTs
Crew: 340

Interwar IJN cruisers

Kuma class (1920)

Scout Cruisers Kuma, Tama, Kitakami, Oi, Kiso

The 6 Kuma class cruisers, of the great armament plan of 1916, entered service too late to participate in the conflict, the last in 1921. They were enlarged versions of the two Tenryu, with a reinforced armament of 3 pieces 140 mm, they were more powerful and faster, but accusing a displacement of 1500 tons higher. They were a compromise between light cruisers and scout ships.

The class included the Kuma, Tama, Kitakami, Oi, and Kiso. Kuma and Tama received seaplanes and a catapult in 1934-35, their rear mast became tripod, the hull was reinforced, the Kitakami seeing its front funnel raised while the others saw themselves grafting different funnel heads. Their foremast superstructures were enlarged. They received four additional 25 mm in 1938-39, and their Torpedo tubes pwere upgraded to 610 mm instead of the initial 533 mm. The displacement thus increased by 200 tons, their speed, initially 36 knots, fell to 33.

Following the very aggressive naval tactics in vogue at the time, the Oi and the Kitakami ferret converted into torpedo cruisers, an old concept fallen into oblivion and refreshed with these versions equipped with 10 quadruple banks of torpedo tubes (40 in total), mounted on 60-meter-long hull side extensions and losing their main artillery. They returned to service in December 1941. Kitakami gained two additional 25mm twin mounts, as well as two 127mm AA twin turrets, and in 1943 she lost four torpedo banks. Severely damaged by the English submarine HMS Templar in 1944, she will be rebuilt as a kaiten transport, losing part of its machinery, replaced by a hold, a crane and a workshop for these eight piloted torpedoes. She survived the war and was BU in 1947, while the Oi was sunk in July 1944, Kiso in November 1944, Tama in October 1944, and Kuma in January 1944.


Displacement: 5,650 t. standard -6,200 t. Full Load
Dimensions: 158.6 m long, 14.2 m wide, 4.8 m draft
Propulsion: 2 shafts, 4 Gihon turbines, 12 Kampon boilers, 90,000 hp=32 knots
Armor: 32 to 62 mm
Armament: 7x 140 mm guns, 4x 25 mm AA guns, 4×2 610 mm TTs, mines, 1 aircraft
Crew: 450

Nagara class (1921)

Scout Cruisers Nagara, Isuzu, Natori, Yuru, Kinu, Abukuma

Isuzu rebuilt in 1944
IJN Nagara:

IJN Isuzu: She was built at the Uraga Dock Company. She was commissioned on 15 August 1923 and participated in the second war with China, covering landings in China, and the capture of Hong Kong. Reassigned to the Dutch East Indies, for the landings and battle of Java, she also later took part later in the Solomon Islands campaign. She was present at the Battle of Santa Cruz and the Naval Battle of Guadalcanal. Almost sunk due to air attacks in late 1943, she headed back to Japan to be rebuilt into an anti-aircraft and anti-submarine cruiser. She participated in the Battle of Leyte Gulf, sunk later by a “wolfpack” of three US submarines and one British, off Sumbawa, 7 April 1945.
IJN Natori:
IJN Natori was built by the Mitsubishi Naval Yard in Nagasaki, commissioned on 15 September 1922. In 1937 and afterwards, she covered troops landings in China and in early 1942, took part in the Phillippines invasion. She also took part in the Dutch East Indies campaigh, notably contributing during the Battle of Sunda Strait, to torpedo the cruisers USS Houston and HMAS Perth. Next she stayed patrolling in the Dutch East Indies waters before a refit and repairs in Japan after air attack in June 1943. She was back in service by April 1944, sunk off Samar by USS Hardhead, on 19 August 1944.
IJN Yura:
IJN Yura was commissioned at Sasebo Naval Arsenal, on 20 March 1923. She was pat of the fleet shadowing Force Z (Prince of Wales and Repulse) in december 1941. Later in January 1942 she covered the landings of Japanese troops in Malaya and Sarawak. She also took part in the Indian Ocean raid, and was part of Nagumo’s escort at the Battle of Midway. She also later took part in the Battle of te Eastern Solomons. Badly damaged after a sever air atack in the Solomons, she was scuttled to prevent capture on 25 October 1942.
IJN Kinu:
IJN Kinu was completed at Kawasaki Shipbuilding Corp., Kobe, on 10 November 1922. She was part of the fiorce shadowing Prince of Wales and Repulse and like her sister Yura also took part in the landings of Japanese troops in Malaya and the Dutch East Indies. She took part in many combat missions in the Solomon Islands and the Philippines. She was ultimately sunk by USN aviation in the Visayan Sea, on 26 October 1944.
IJN Abukuma:
Last of the Nagara class, IJN Abukuma came from the Uraga Dock. She was commissioned on 26 May 1925, part of the escort force assigned to the kido Butai at Pearl Harbor. She was later also the sole Nagara class ship at the Battle of the Komandorski Islands (north pacific), remaining active in northern waters until October 1944. She was rushed south to oppose the American invasion of the Philippines, caught and attacked, severely damaged by ambushing American PT boats, at the Battle of Surigao Strait (25 October) finished off by land-based bombers and eventually scuttled on 26 October 1944.

Sendai class (1923)

Light Cruisers Sendai, Jintsu, Naka +5 cancelled

The cruisers of the Sendai class were very close in their general design compared to the previous Nagara, but with larger dimensions, new machinery for greater speed traduced in a new funnel. The fourth of the class, 1st batch, IJN Kako, was broken up soon after launch, as the following 2nd batch because of the Washington Treaty limitations, just signed.
The three cruisers received a catapult for reconnaissance in 1929, and by 1943, a powerful AA. All were sunk in action, Naka in February 1944 during the air raid on Truk, Sendai by aviation after the Battle of the Bay of Empress Augusta, and Jintsu by gunfire at the battle of Kolombangara.
Displacement 5,200 t. standard 7,100 t. Fully Loaded
Dimensions 163 x 14,17 x 5m (532 x 46 ft 6 in x 15 ft 9 in or 29 ft FL)
Propulsion 2 shafts, 4 Gihon turbines, 12 Kampon boilers, 90,000 hp, 154kW 110V electrical
Speed 35,2 knots (65.28 km/h; 40.56 mph)
Range 5,000 nmi (9,300 km; 5,800 mi)/14 knots (oil 1010 tons, coal 570 tons)
Armament 7x 140mm/50, 2x 76mm, 2x 13.2mm AA, 4×2 610 mm TTs, 1 seaplane, 80 mines
Protection Armor scheme – 28 to 65 mm, see notes
Crew 450 (1925)

IJN Yubari (1924)

Light cruiser

IJN Yūbari (夕張) was not only the very first IJN post-WW1 design, but it was an experimental light cruiser whose idea dated back from 1917 and started in 1922, and when she was completed in 1923 for the Imperial Japanese Navy, she marked a large step forward in the nation’s cruiser design. Designed by famous engineer Yuzuru Hiraga, she was largely seen as a test bed for new designs and technologies in a post-Washington Naval-treaty, tonnage restrictive environment. Nevertheless, she was commissioned and had a quite active career in many operations during the Pacific theatre of WW2. Yūbari’s designs and innovation would find their way into many future IJN warships, from destroyers to cruisers. During the war, she took part in the most vicious fights in the South Pacific, notably participating in the whole Solomons campaign, from beginning to the end at Rabaul in 1944. She was commanded from 1940 to 1942 by captain Masami Ban, and until 1943 by Taiji Hirai, before in 1944 being handed to Morie Funaki until 1944 and finally, to Takeo Nara for two months of her life.
Displacement 3,315 t. standard -4,447 t. Full Load
Dimensions 139 m long, 12 m wide, 3.6 m draft
Propulsion 3 shaft turbines and 8 boilers, 57,500 hp, 34 knots
Armor: Armored Deck and belt 16-22-25-28 mm, gun shields 11 mm, ammo wells 32 mm
Armament: 6x 140 mm (2×2, 2×1), 1× 76mm/40 AA, 2×2 610 mm TTs, 2x 7.7mm MGs, 34 mines.
Crew: 350

Furutaka class (1925)

Light cruisers Furutaka, Kako

The first Japanese “washington” cruisers, were also two “heavy cruisers”. The Furutaka class were the first built by the Japanese Navy after the Washington Treaty. Their main feature was the presence of a continuous deck with two successive recesses, a measure to save weight to optimize speed, but also the choice of an artillery in six simple turrets.
This singular configuration did not proved advantageous and the two ships were rebuilt in 1936-39. Significant changes included the more rational choice of double turrets, reconstructed superstructures and bridge, and lateral torpedo tubes. 12 tubes, 6 twin banks two on each side replaced by two quadruple banks.

A catapult was also fitted, as well as the installation of anti-torpedo ballasts, the reinforcement of the overall protection and the AAA, with a tonnage passing from 7,100-8,450 tons to 8,700-10,340 tons. Originally, this AA artillery consisted of only four 100 mm pieces and two heavy machine guns. In 1932 these were replaced by QF 120 mm fully shielded in half turrets, while 25 mm guns and other heavy 12.7mm machine guns were added to this range.

By the new standard they imposed, the Furutaka led to the Aoba, barely larger, but improved. They participated very actively in the Japanese operations, particularly in the Solomon Islands, and were both sunk, the Furutaka off the island of Savo, Guadalcanal, during the battle of Cape Hope the night of October 11 to 12, 1942, being part of the “Tokyo Night Express”, by the American cruisers of Admiral Scott. The Kako was torpedoed and sunk near Kiaveng (New Britain) by the old American submarine S44, August 10, 1942. She participated shortly before the great victory at Savo Island.
Displacement 8 700 t. standard -10 340 t. FL
Dimensions 183,53 x 19,93 x 5,61m
Propulsion 4 shafts turbines, 12 boilers, 102,000 hp, 33 knots
Armor: 25 to 76 mm
Armament: 6x 152 (3×2), 4x 120, 8x 25 AA, 4x 13.2 mm HMG AA, 8x 610 mm TTs (2×4), 2 seaplanes
Crew: 730

Aoba class (1925)

Heavy Cruisers Aoba, Kinugasa

The two Aoba-class heavy cruisers followed the Furutaka a year apart, so their development did not take into account the shortcomings of the two previous ships. They had from the start three twin turrets and twin 5-in DP guns. On the other hand, their torpedo tubes were still two triple fixes per side. A first modification intervened in 1932: They received four twin 13.2 mm (0.5 in) cal. HMGs. By 1938-40, their fixed tubes were replaced by two quadruple banks on deck, and to compensate for stability (and future upgrades), they were fitted with side ballast tanks. Their AA was reinforced with 25 mm cannons, four more heavy machine guns, bringing the total to 12.

In operations, the two ships were seen in all major operations. Particularly active in the Solomons, they notably participated in the “massacre” of Savo Island on the night of August 8, 1942. IJN Kinugasa was sunk by USN aviation on November 14, 1942 during the second Battle of Guadalcanal, while Aoba survived long enough to see her armament increase to fifteen 25 mm AA guns, then forty-two two months later in May-June 1944. She received a radar but the two banks were removed. She saw the Battle of the Coral Sea, the first Battle of Guadalcanal, and second, and was destroyed eventually by the US III Air Fleet while moored in Kure Naval Base, on July 25, 1945.


Displacement: 7100 t. standard -8760 t. Full Load
Dimensions: 183.58 m long, 15.83 m wide, 5.71 m draft
Propulsion: 4 shafts Kampon Steam turbines, 12 boilers, 102,000 hp, 34.5 knots
Armor: 25 to 76 mm (2-3 in)
Armament: 3×2 6-in(203mm), 4x 120mm, 8x 25 AA, 4x 13.2 mm AA, 6×2 610 mm TTs, 1 aircraft
Crew: 625

Nachi class (1925)

The Nachi: First true IJN heavy cruisers

The heavy cruisers of the Nachi class laid down between 1924 and 1925 and completed in 1928-29, were at the very limits of the Washington Treaty, yet they managed to bear a five turret arrangement never seen on a ship of this type before, and imposing to the IJN new standard, not followed internationally but coherent with Japanese retirement of the league of nations.
This feat consisted of being able to stack five twin turrets for 8-in/203 mm guns and 12 torpedo tubes on a cruiser more than 200 meters long, but which ultimately displaced only the 10,000 tons required by the treaty. They could reach 35.5 knots without excessive power either. The secret laid partly in their amazing width/lenght ratio almost unchanged from the Aoba, about the same 12/1. Their protection was greatly improved however with an inner armoured citadel ad a triple hull plus reinforced coss-sections and a reduced but reinforced bulkhead. In fact, the final tonnage as for 1941 was 11,000 tons.

IJN Ashigara an the Gref Spee in the background at Kiel in March 1937. Colorized photo by Hirootoko JR.

1930s et 1940s refit

In 1934-36, their single 120 mm single mounts gave way to new 127 mm (5 in) twin turrets, their fixed torpedo tubes replaced by quadruple rotating banks, while the AA was reinforced by four additional 13.2 mm machine guns and two catapults were installed on the sides to launch reconnaissance floatplanes. In 1940-41 there was a second overhaul concerning the masts and superstructures, the addition of 8 x 25 mm AA guns and especially two new quadruple torpedo tubes on the flanks, for a total of 16, a record for a cruiser, but in the typical trend of aggressiveness of the Japanese tactics at the time. This forced to add imposing bulges in order to safeguard their stability.

IJN Nachi in Yokosuka in the 1920s. Colorized photo by Hirootoko JR.


Displacement 13,000 t. standard -14,740 t. Full Load
Dimensions 203.76 m long, 20.60 m wide, 5.66 m draft
Propulsion 4 propellers, 4 turbines, 12 boilers, 130,000 hp.
Top speed 34 knots
Armour from 100 to 25 mm
Armament 10 guns of 152 (5 × 2), 8 guns of 12, 8 of 25 AA, 12 mitt. 13.2 mm AA, 16 TLT 610 mm (4 × 4), 3 aircraft
Crew 773

The Nachi class in action

In operations, these four ships, the IJN Nachi, Myoko, Ashigara and Haguro proved formidable combatants, very actively employed, and which defeated all their American, British and Dutch opponents until 1943. The Myoko was apparently the only one to have been camouflaged. These Nachi class cruisers participated in the battle of Leyte, where the Nachi, in the confusion and fury of the attacks, collided and seriously damaged the Mogami.
Shortly before this battle, their AA armament had reached fifty-two 25mm guns, at the cost of removing two banks of torpedo tubes. They survived the battle of Samar (Leyte), the Nachi being sunk in November 1944 off Manila by USN air attacks, while IJN Myoko, already badly damaged in Leyte, was torpedoed by USS Bergall in December 1944 but survived.
She sank in shallow waters in the Strait of Malacca, and her wreck was dynamited in 1946 to allow trade to resume. IJN Haguro and Ashigara were sunk respectively in May and June 1945, one by the torpedoes of British destroyers off Penang during the reconquest of Malaysia, while the second was torpedoed by British submarine HMS Trenchant in the Bangka Strait.

Myoko 1944 – author’s schematics

Cruiser Myoko on sea trials in March 1941 in Sukumo Bay. Colorized photo by Hirootoko JR.

Takao class (1930)

Heavy Cruisers: Takao, Atago, Maya, Chokai

The Takao class of heavy cruisers, laid down in 1927-28, launched in 1930 and completed in 1932, comprising the Takao, Atago, Maya and Chokai were among the best and most active Japanese cruisers of World War II. They derived from the Nachi, from which they took over the essentials, with however better protection, including their armored decks, an increase in the main parts and banks of quadruple rotating torpedo tubes from the outset. Moreover, their standard displacement was even lower than the Nachi, at 9,850 tons instead of 10,000, which compared to comparable American cruisers was exceptional. They put their excellent provisions to the test of fire and resisted very well the impacts of American buildings during the hard engagements of 1942-44. Their footbridge was notably very different from the Nachi, affecting much fuller and more solid forms, very characteristic with their three superimposed footbridges.

In 1939-40, Takao and Atago received two additional quadruple banks of torpedo tubes, bringing the total to 16, received side ballast tanks, and the doubling of their secondary artillery, including the addition of 8 x 25 guns. mm YY. Their original measurements were 201.67 meters long by 18 wide and 6.11 draft for 12,780 tons fully loaded. Compare with their 1941 file. Chokai and Maya, on the other hand, received neither the additional torpedo tube banks nor the 25 mm guns. On the other hand all saw their AA artillery increase considerably. On the eve of the titanic battle of Leyte, they had 60 to 66 25 mm AA guns.

In operations, these four ships were the spearhead of the Japanese Navy, participating in most important engagements. All four were engaged in Admiral Kurita’s shock squadron under Toyoda during the Battle of Leyte in October 1944. The squadron was spotted on October 21 by American submersibles, and attacked on the evening of the 23rd. by the USS Darter and Dace, confirming their presence. They torpedoed and sent the Atago and the Maya to the bottom. The Darter then went after the Takao, who survived three shots on goal and barely made it back to Brunei, before heading to Singapore for further repairs.

Finally, Chokai, the same day, was taken to task by the American naval aviation, hit by several bombs from the Curtiss Helldivers, it was finally disabled and attacked by the American destroyers who opened fire at close range and finished it off. The Takao therefore escaped the battle of Samar and was repaired but condemned to inaction in the harbor of Singapore. She was sunk on the spot by the British Navy commandos using the pocket submersible XE3, who placed charges against her hull, on July 31, 1945. An operation which was the subject of a film. In October 1946 she was refloated, towed and laid up in the Strait of Malacca.
Displacement 13,400 t. standard -14,600 t. Full Load
Dimensions 203.76 m long, 20.73 m wide, 6.11 m draft
Machines 4 propellers, 4 turbines, 12 boilers, 130,000 hp.
Maximum speed 34.2 knots
Armor From 130 (magazines) to 25 mm
Armament 10 x 203mm guns (5×2), 8 x 127mm guns (4×2), 8 x 25mm AA, 6 mitt. 13.2 mm AA, 8/16 TLT 610 mm (2/4×4), 3 aircraft
Crew 773

Ioshima class (1937)

Light Cruisers Ioshima, Yashoshima

The Ning Hai class cruisers were the culmination of many “firsts” and “lasts”: First cruisers of the feldgling Chinese Republic, first built in Japan, and last Chinese cruisers overall (although arguably the new Type 055 missile destroyers of the actual PLAN us locally called Renhai-class cruiser). The Ning Hai were in fact the only cruisers built for the Chinese Navy since the fall of the Empire in 1911, followed by a first repulic, the warlord era, and a more or less stabilized republic again, allowing to plan a modenrization of the fleet. Indeed in 1937, at the time of the start of the second Sino-Japanese war, after a quasi-war in the north since 1932, the Chinese Navy was in dire straits, with on paper a fleet of cruisers and gunboats dating back from twenty years and more.

They had received little modifications between them and were hopelessely obsolete and outmatched by the IJN. Both ships had a very short career under Chinese flag, both were sunk in the Yangtze River on 23 September 1937, by Japanese aviation. They were refloated and later repaired by the Japanese, and pressed into service in the IJN where they spent the rest of their career. Originally planned for transfer to the puppet government of Wang Jing-Wei, they were outfitted as barracks hulks and later the escort ships IJN Ioshima and Yasoshima, in 1944. Both were lost in action to USN torpedoes the same year.

Specifications (as Yasoshima class 1942)
Dimensions 109.7m oa x 11.9m x 3.96m
Displacement 2165 standard, 2500 tons FL
Propulsion 2-3 shafts 2/3 VTE, 4/2 Kampon boilers, 9,000 hp
Speed Top speed 22.2 knots (25 mph; 40 km/h)
Range 5,000 nmi (9000 km) at 12 kn
Armament 2 x 1 – 120/45 10-shiki, 5 x 3 – 25/60 96-shiki, 2 DCR (18)
Electronics 2-shiki 2-go radar, 93-shiki sonar
Armor belt 2-in (25 mm), Deck 2.8 in (19 mm)
Crew 340

Mogami class (1937)

Light Cruisers: Mogami, Mikuma, Suzuya, Kumano

Mogami at Kure in July 1935 trials

The Mogami class cruisers (Mogami, Mikuma, Suzuya, Kumano), launched in 1934 (1936 for the Kumano) and completed in pairs respectively in 1935 and 1937 at the Kure, Mitsubishi (Nagasaki), Yokosuka and Kawasaki (Kobe) shipyards, suffered delay resulting from the tests carried out with the first two, which were victims of vibrations due to the structural weakness of their hull, so bad that the turrets were unusable. The last two were therefore overhauled and reinforced, receiving ballast for their stability, while the first two went back to drydock in 1936-38 for the same modifications. They were classed as light cruisers due to an initial standard displacement of 8,500 tons, 15 x 155mm guns in five triple turrets like contemporary Brooklyn class and capable of 37 knots. However, by their dimensions, they were more similar to heavy cruisers.

In 1939, they displaced 11,200 tons as standard, or 3,700 tons of various reinforcements. During a second series of modifications at Kure in 1939-40, they became real heavy cruisers, their 155 guns being abandoned in favor of an armament of 5 twin 203 mm turrets. Their width increased and their protection was further improved. Their AA artillery, initially composed of 8 double turrets of 127 mm and 4 pieces of 40 mm passed to 20, then 30 guns of 25 mm AA, and finally 50 for the survivors on the eve of the battle of Leyte. Always with the aim of safeguarding stability, their torpedo tube mountings were triple and not quadruple, but there were always 4 of them. come.

IJN Mogami and Mikuma were engaged in the Battle of Midway in June 1942 under the command of Admiral Yamamoto. But this time luck had changed sides, and the two ships were seriously damaged, first in the confusion of the night, by a serious collision on June 6, 1942, at 2:15 a.m., then around 5 a.m., when the The Admiral had ordered the withdrawal of the fleet, by the US Navy’s SBD Dauntless dive bombers. The Mikuma did not survive and sank, while the Mogami was also attacked later that day. It survived there and dragged itself to Kure for year-long refits. We took the opportunity to rebuild it into a hybrid aircraft carrier, capable of carrying 11 seaplanes, including torpedo planes, and A6M2N Rufe fighters, in order to provide cover to the squadrons. In 1943, he returned to service with a DCA composed of 30 25 mm guns in fifteen double mounts.

This reconstruction had inspired the Admiralty who decided to order the construction of two buildings of the same type, the Ibuki class, but only one of which was completed, and as a fast aircraft carrier. The Mogami was engaged in the Battle of Surigao Strait shortly after, and was there on this occasion manhandled by the fire of the American cruisers. All three (Mogami, Suzuya and Kumano) were also present during the Battle of Samar near Leyte in the Philippines in October 1944. The Mogami sank on October 25, completed by Grumman TBM Avenger torpedo bombers. The Suzuya was also doomed to the same end, while the Kumano survived it. He tried to flee from patrols for a month and was finally spotted and bombarded by other aircraft on November 25, exactly one month after his twins went missing. The last one, Ibuki, was converted into a fleet aircraft carrier, but never completed.

Displacement 12,400 t. standard -13,670 t. Full Load
Dimensions 201 m long, 20.50 m wide, 5.9 m draft
Machines 4 propellers, 4 turbines, 12 boilers, 152,000 hp.
Maximum speed 35 knots
Armor From 130 (magazines) to 250 mm
Armament 10 guns of 203 mm (5×2), 8 guns of 127mm (4×2), 2 guns of 40 and 20 of 25 mm AA, 6 mitt. 13.2 mm AA, 12 TLT 610 mm (4×3), 3 aircraft
Crew 850

Tone class (1939)

Hybrid Cruisers: Tone, Chikuma

IJN Tone, May 27, 1942
The Tone-class cruisers (Tone and Chikuma) were part of the 1932 supplemental plan to include light cruisers under the terms of the Washington Treaty, but in 1938-39, with the approach of hostilities, it was decided to terminate them as cruisers heavy. Their triple 155 mm turrets were not retained and they were reinforced considerably. However, their great originality lay in their hybrid nature, with all their pieces concentrated in the hunt (at the front), leaving their aft deck free of any accommodation intended to operate squadrons of reconnaissance seaplanes.

After modifications, changing to four twin 203 mm turrets, they still remained as powerful as the standard heavy cruisers in service in the world. They were to be used as scout cruisers and inspired the reconstruction of the Mogami in 1942. However, they did not have a real large hangar and therefore could only operate 5 to 6 seaplanes. Their anti-aircraft artillery initially consisted of 12 25 mm guns in six double mountings, then it quickly increased to 30 at the start of the conflict. The Tone ended the war with 57 25 mm guns, which did not prevent her from being sunk.

IJN Tone was at Midway in June 1942, then participated as her twin in the Battle of the Eastern Solomons in August 1942, from the Santa Cruz Islands, in the second battle of Guadalcanal in November 1942. The Tone and the Chikuma were finally engaged in the battle of Leyte in October 1944, under the command of Admiral Kurita. The Chikuma suffered attacks from US Navy aircraft and sank on October 25. The Tone survived there, but it was only to perish under the bombs of other planes in the bay of Kure during the great raids of the III Air Force on July 24, 1945. It was plasticized and its remains desoldered in situ in 1948.

Displacement 12,400 t. standard -15,200 t. Full Load
Dimensions 201.5 m long, 18.50 m wide, 5.9 m draft
Machines 4 propellers, 4 turbines, 12 boilers, 152,000 hp.
Maximum speed 35 knots
Armor From 130 (magazines) to 25 mm
Armament 8 x 203mm guns (4×2), 8 x 127mm guns (4×2), 30 x 25mm AA guns, 12 x 610mm TLT (4×3), 5 aircraft
Crew 850

Katori class (1941)

School Cruisers: Katori, Kashima and Kashii

The three units of this class, Katori, Kashima and Kashii, were designed as training cruisers, and base buildings for destroyer and submarine flotillas. Short, wide, slow, and under-armed, they were of low military value but were nevertheless engaged in combat with an increased armament, including three twin turrets of 76 mm AA, and 25 25 mm guns, the tubes torpedo boats being landed. It was further increased by 5 pieces of 25 mm AA and various heavy machine guns, the catapult being in turn dismounted. Katori, damaged near Truk Naval Air Station, was completed by US Navy units in April 1944, Kashii torpedoed and sunk by an Avenger in the China Sea in January 1945, and Kashima survived the war, BU in 1947.

Displacement 5,890 t. standard -6,500 t. Full Load
Dimensions 129.77 m long, 15.96 m wide, 5.75 m draft
Machines 2 propellers, 2 turbines, diesel engines, 3 boilers, 80,000 hp.
Maximum speed 18 knots
Bridge shielding 50 mm
Armament 4 x 140 guns (2×2), 1×2 x 76 guns, 4 x 25 mm AA, 4 x 533 mm TLT (2×2), 1 aircraft
Crew 160+200 students

Agano class (1941)

Light Cruisers Agano, Noshiro, Yahagi, Sakawa

The last IJN light cruisers

Blueprint Agano 1942
The Agano were the last Japanese light cruiser built in serie, and the fourth of the class, IJN Sakawa, was completed in December 1944, as the very last Japanese cruiser as after the war, shipyards only delivered “destroyers”. This Class included the Agano, launched in 1941 and completed in 1942, Noshiro and Yahagi, launched in 1942 and completed in 1943 and finally the Sakawa, launched in 1944, due to various delays. Classified as light cruisers, they were part of an extensive program to replace older cruisers such as the twenty-year-old Kuma, Nagara and Sendai classes. The Agano, as it appeared at its entry into service.
They were also planned as destroyers leaders. They were therefore light but fast at 35 knots, with a reconnaissance capability (two seaplanes), and yet still an armament able to cope with enemy destroyers. They added a large AA battery composed of 25 mm in single, twin, triple mounts for up to 61 on Sakawa in 1945. Three were sunk in action, Agano in February 1944, Noshiro in October 1943, Yahagi (rearmed with 52 guns i 1944) in April 1945. IJN Sakawa survived the conflict, but was quickly integrated into the small fleet gathered in Bikini Atoll to be blasted at the July 2, 1946 “Able” nuclear test.

Agano 1942 – Author’s HD profile illustration

Author’s profile illustration Yahagi 1944


Displacement 6,550 t. standard -8,530 t. Full Load
Dimensions 174 m long, 15,20 m wide, 5,63 m draft
Propulsion 4 shaft, Kampon turbines, 6 boilers, 100,000 hp.
Top speed 35 knots
Armor from 50 to 85 mm
Armament 6 x 152 (2 × 3), 4 x 100 (2 × 2), 32 x 25 AA, 16 DCT, 8 x 610 mm (2 × 4) TTs, 2 seaplanes
Crew 730

IJN Agano: Completed on 31 October 1942, she took part in the Guadalcanal Campaign and Solomon Islands battles of 1943. IJN Agano however was badly damaged in Rabaul durring a US air strike, hit by the air groups from USS Saratoga and Princeton. Later, still in repairs there, she was attacked again by aicraft from TF38 on 11 November, receiving a torpedo hit. While underway for home island and drydock repairs, she was ambushed, torpedoed and sunk north of Truk, by USS Skate (SS-305) on 16 February 1944.
IJN Noshiro: She was Commissioned on 30 June 1943, seeing the Solomon Islands Campaign but damaged during the USN raids on Rabaul, on 5 November 1943. Back in the Marianas in the summer of 1944 she took part in Admiral Kurita’s force bold sweep at the Battle of the Philippine Sea. She was sunk at the Battle of Leyte Gulf in October 1944. She sailed west of Panay while withdrawing from Samar, when spotted on the morning of 26 October by aircraft from USS Wasp and USS Cowpens, strafed, bombed and eventually sunk on 26 October.
IJN Yahagi: She was Commissioned on 29 December 1943, seeing action in the Marianas Islands in May and June 1944. She took part in the Battle of the Philippine Sea in june, and the Battle of Leyte Gulf in october, but survived both. While the invasion of Okinawa was taking place, she was assigned to a desperate task forced centered around IJN Yamato on 1 April 1945, a suicide mission against the amphibious fleet off Okinawa. The task force was spotted en route and IJN Yahagi was caught by multiple air groups, hit by some seven torpedoes as well as a dozen bombs, leving her no chance. She sank in the afternoon, 7 April 1945.
IJN Sakawa: Completed at the end of 1944, little fuel available, IJN Yahagi was practically inactive, so her crew had plenty of training when she was used for a few sweeps along the coast, exchanging fire on some occasions with passing by US planes. She survived the war. Used as a transport to return demilitarized troops from New Guinea and ther islands until took on the disposal list by the US, she was seized and pressed into the atom bomb tests at Bikini Atoll, in 1946.

Oyodo class (1942)

Light Cruisers Oyodo, 8 more planned (cancelled)

She was one of the last cruiser of the Empire, the very last being the fourth Agano class. Initially designed as a hybrid scouting cruiser on the same principle as IJN Tone, yet lighter, cheaper and faster to build, she was tailored to carry and operate specifically six Kawanishi E15K long-range seaplanes, fitted with a 45-meter (147 feet) long aft catapult, to screen forward of oceanic submarine fleets.

Her armament comprised two triple 6-in guns (155 mm) at first, same as the Mogami-class, but as the war progressed, she was rearmed with two surplus twin 8-in turrets, so just four in all. At her completion in February 1943, planned long range operations, notably against the Panama Canal by large Japanese carrier submersible were very compromised. Also, her own planned seaplanes were still not operational. The admiralty decided to fit her instead a more standard catapult and standard model floatplanes. The large hangar was no longer used, and she operated with just two aircraft.

Due to her reduced military value, IJN Oyodo saw little fighting. Twelve ships of the same class were initially planned for the 1939 and 1942 naval plans, none being built, or even laid down. IJN Oyodo received a better AA as the war progressed: In in 1945 this went up to fifty-two 25 mm AA in triple, twin or single mounts. This did not prevented her eventual fate: In 1945 she was anchored in kure, short of fuel, when USN aviation straddled then sank her in the harbor, on July 28, 1945. As the the last survivors of the Imperial Navy’s cruiser, she was broken up after the war, but the modern JMSDF took inpiration of her for large ASW helicopter desoroyers of the 1970-90s.

Author’s profile illustration Oyodo 1944
Displacement 8,164 t. standard -10 252 t. Full Load
Dimensions 192.10 m long, 16.60 m wide, 5.9 m draft
Machines 4 propellers, 4 turbines, 6 boilers, 110,000 hp.
Top speed 35 knots
Protection 50 to 25 mm
Armament 6 x 155 mm (2 × 3) guns, 8 x 100 mm (4 × 2) guns, 12 x 25 mm AA guns, 2 planes
Crew 600

Ibuki class (1944)

Light Cruisers Ibuki, Ikoma, +2 unnamed.

IJN Ibuki being scrapped in 1947

The Ibuki-class (伊吹型) cruisers were the last Japanese heavy cruisers and to gain in design time, they were essentially repeats of Mogami class. The lead ship IJN Ibuki was the only one advanced enough to be launched, but after Pearl Harbor it was decided to convert her into a light aircraft carrier. However this progresses slosly until she was suspended in 1945, and scrapped the following year. The -still unnamed- “N°301” was scrapped a month after being laid down to clear the slipway and start a new aircraft carrier.
This will be the object of a dedicated post in the future.
12,220/14,828 t FL, 200.6 x 20.2 x 6 m (658 ft 2 in x 66 ft 3 in x 19 ft 10 in). 4 shafts GST, 8 Kampon WT Boilers 152,000 shp (113,000 kW) =35 knots RA 6,300 nmi/18 kts, Crew 876. One Type 2, Mark 2, Model 1 air search radar and Type 93 hydrophone system as planned, 5×2 8 in, 4×2 5 in DP, 4×2 1 in AA guns, 2×2 0.52 in Type 93 HMGs, 4×4 24 in TTs, 2 catapults, 3 floatplanes.
Armor belt 1.2–5.5 in, Deck 1.4–2.4 in, turrets 1 in, Barbettes 1–3.9 in CT 4 in

As converted as an aircraft carrier, 1945 Specs as an aircraft carrier

Projected Cruisers

Combining the interwar and WW2 there were many alternative designs. However given the systematic destruction of archives at the end of WW2, there are not many around to gaze and discussed upon.
Let’s cite the following, for which at least some data is known:
Light Cruisers Design C-19 (1912) Primary minelayer cruiser design before WW1, not voted or ordered. Dimensions 159,41 (pp) x 15,24 x 5,18 meters, displacement 6.000tons (standard) prop. 2 shafts GST 28.500shp, 27 kts, RA 18.500km (10.000nm). Same armament as the Tenryu and 100 mines.
Light Cruiser Design C-31A (1915): Wartime design, well armed cruiser preliminary to the Tenryu class and proposed 1914 large scout cruiser.
Dimensions: 161,54 (pp) x 15,85 x 5,1 m for 7.000tons, 4 shafts GST 106.000shp, 35 kts, RA 9.200km (5.000nm), protected by 25mm Deck, 76mm Belt and armed with nine single shielded 140mm Guns (repartition unknown) and triple 533mm TTs, 48 mines.
Light Cruiser Design C-32 (1915): Smaller, leading to the Tenryu design: 140,21 (pp) x 13,41 x 4,11 m for 4.100tons, 4 shafts 65.000shp 34 kts and 11.000km (5.900nm), protected by 25mm Deck, 63mm Belt and armed with 5×1 140mm and 2×3 533mm TTs, 48 mines.

Armoured Cruiser of 7.200 ton Proposal (1916) The last IJN armored cruisers ever, although still doubling as scout cruisers. Planned in 1914 but slow construction timetable delayed them to 1916 and the design was reformulated to three 7.200 ton cruisers as part of the 8-4 and 8-6 naval programmes. Never built but considered as very early steps in the Furutaka class since the 20cm guns were considered for them. Displacement 7.200tons, 36 kts and RA 11.000km (8.000nm), prot. 51mm Deck, 76mm Belt, four twin and a single 140mm Guns, four twin 610mm TTs

Light cruiser Tenryu-Kai type (1917): 6 modified or improved Tenryu class cruisers were considered to be built from 1917 onward as part of the 8-4 and 8-6 naval programmes. Their designer was Teiji Kawase and only very limited info I could gather was that it’s displacement would be 3.500tons compared to 3.230tons of the Tenryu class which indicate more armour somewhat more armament and larger 610mm torpedo tubes with the associated increased engine power.

Furutaka Class original Design (1918): The design process eventually leading the creation of the Furutaka class Heavy Cruisers was first started with a smaller ship evolved from the previous 7.200ton design to 8.000tons and 5-6 twin 140mm guns in a pyramidal arrangement while the AA armament only consisted of 2 single 76mm guns while the torpedo armament unchanged from the 4 twin 610mm tubes. Armour wise it was much thinner as well with the armoured box protecting only the machinery by 64mm belt and 25mm deck. Eventually based on the data of the USN’s Omaha class but especially on the British Hawkins class, this design evolved into the IJN’s first heavy cruiser type.

Tenryu-Kai type (1921): A different source provides more data on the Tenryu-Kai type cruiser putting it to 1921 and with somewhat more displacement. Dimensions 143 (oa) x 12,4 x 4 m for 4.080tons, 3 shafts GST 51.000 shp 33 kts and 11.000km (8.000nm), prot. 25mm Deck, 63mm Belt, 2×2 140mm, 1x 76mm AA, 2×2 610mm TTs.

Heavy cruisers Design C-41 (1923) From Yuzuru Hiraga perosnal archives, very early Nachi class design. Their armament was weak compared to the tonnage, so they probably would have been brushed aside by the admiralty. More
Dimensions: 225,5 (pp) x 21,64 x 5,33 meters, Displacement: 14.000 tons (standard) 18.000 tons (Full load). Prop. 4 shafts GST 140.000shp 36.5 kts
Armour: 25/47mm Deck, 51/102mm Belt (Magazines/Machinery)
Armed with 4×2 200 mm/50 Type 3, 2×1 120mm/45 Type 10 DP, 2×4 610mm TTs.

Heavy cruisers Design C-42 (1923) Another, same initial design process, smaller and slower but armed the same way and better protected:
Dimensions: 210,3 (pp) x 20,11 x 5,26 meters, Displacement: 12.000 tons (standard) 15.200 tons (Full load), 4 shafts GST 125.000shp 36 kts, RA 14.800 km (8.000 nm)
Armour: 25/47mm Deck, 51/102mm Belt (Magazines/Machinery)

Nachi Preliminary Design (1924): Singular with their well armoured triple and quadruple turrets, slightly shorter hull, thinner armour
Dimensions 198,12 (pp) x 17,52 meters, displacement: 10.000tons (standard), prot. 38mm Deck, 89mm Belt, armed with 4×3/3×4 200mm/50 Type 3, same as above.
Nachi Preliminary Design 3 (1924): Same but longer range, 5×2 200mm/50 Type 3 Guns

Squadron leader Design C-43 (1923): Proposal found in the Yuzuru Hiraga archive but likely Hiraga’s own design number because C-42 was Oyodo and C-44 was the Agano-Kai. Might be connected to the earlier 5.600ton design. Source
Dimensions: 152,4 (pp) x 14,17 x 4,85 m for 5.600tons (standard) 7.000tons (Full load). Prop. 3 shafts 42.750 shp GST, 35 kts RA 9.200km (5.000nm). Only deck prot. (machinery) 25 mm Deck and 64mm Belt. Armed with 4×2 140 mm, 2×1 76mm DP-AA Guns, 2×2 610mm Torpedo Tubes, 100 Mines.

Light cruiser 5.000 ton Proposal (1926): A well armed true light cruiser on limited displacement and average speed, it’s origins are a mystery but might be connected to the numerous Vickers export designs of the time. src https://iiif.dl.itc.u-tokyo.ac.jp/r…3d88f#?c=0&m=0&s=0&cv=0&xywh=-659,0,8261,4927
Engines: 60.000shp Steam Turbines, 4 shafts, speed: 59km/h (30,5knots)
Armaments: 3×3 152mm, 2×2 120mm DP-AA, 2×2 533mm Torpedo Tubes

Design 1927/C-37 (1927): Earliest proposal in the design linage leading to the Mogami class cruisers.
Dimensions: 197 m wl, Displacement: 8.500tons (standard) 11.200tons (Full load). 4 shafts GST 152.000 shp. Armour: 38mm Deck, 125/143mm Belt (Magazines/Machinery). Armed with 5×3 155mm, 4×1 127mm DP-AA, 4×3 610mm TTs, 2x Scout Planes

Squadron Leader Design (1928): Early light design which led years afterwards to the Agano and Oyodo class. Good speed as lead/scouts for destroyers. 6 planned but cancelled (Four Takao-Kai type planned instead by 1930. Lacroix mentioned they were to be armed with six 50-cal 14-cm guns in twin mounts and high elevation, type planned for the Kongo Replacement designs of 1928-29. So Displacement 5.000tons, prop. 3 shafts GST 42.750 shp 35 kts RA 9.200km (5.000 nm). Armour: 51mm Deck, 76mm Belt, armed woth 3×2 140mm/50 Type 3/140mm/55 Type 88 Guns, 2×3 610mm TTs, 2x Scout Planes

Takao-Kai type Heavy Cruisers (1929): Follow-up design postponed due to the Treaty of London. It is conjectured they had a better heavy AA and improved armour (like 140mm Magazine belt) and the same 5 twin turrets but ported on the new new /55 in development. Mogami style smaller Tower bridge. Probably 12,000 tonnes (10.000 declared).

Tone-Kai type Heavy Cruiser (1938/39) – At the 1938 revised Maru 4 programme, two modified Tone type cruisers were considered to be built to form a homogeneous squadron with the other two Tones. Not much is known about this design except that it was based on the Tone class but with substantial more displacement of 13.000tons standard instead of the 11.200tons of the original Tones which might indicate better armour and engine power and command facilities.
Source: (Eric Lacroix – Japanese Cruisers of the Pacific War), Japanese Wiki

IJN Haguro upgun proposal (1933): New 8-in cannons under development comparable to the USN 8″/55 cannons to be first tested on IJN Haguro and ported on the remainder Takao class ships. Budgetary constraints stopped the development.

Squadron Leader Design (1937) -Earliest precursor of the Agano class, on smaller displacement and Oyodo’s armament, heavy AA. Five ships planned (Maru 3 programme) but not voted.
Displacement: 5.000 tons (standard) speed 36 kts, RA 13.000 km (7.000nm), prot. 100mm Belt, armed with 2×3 155mm/60 Type 90 Guns, 4×2 76mm/60 Type 98 DP-AA Guns, 3×2 25mm/60 Type 96 AA guns, 2×4 610mm TTs, 1 Seaplane.

Kuma Class Torpedo Cruiser Conversion proposal (1938): For the special night attack doctrine to be ported on 3 or all ships. The conversion was done on a modified design on 2 ships during the war. The original proposal had the following armament: 4×2 127mm/40 Type 89 DP-AA guns, 4×2 25mm/60 Type 96 AA guns, 11×4 610mm TTs, 5 per side, 1 centreline. Production of the Type 93 “Long Lance” remained problematic, even more for their launchers and the 127mm DP were in short supplies.

Sq. Leader Design C-39 (1938): Preliminary design for the Agano class light cruisers: Revised machinery, longer range, smaller displacement, new torpedo arrangement, two funnels.
Dimensions 162 (pp) x 173 (wl) x 174,5 (oa) x 15,2 x 5,6 meters, disp. 6.585 tons (standard) 7.800 tons (Full load), 4 shafts GST 112.000 shp 36 kts, RA 14.800 km (8.000nm).
Armour: 20mm Deck, 55/60mm Belt + extra over the Magazines/Machinery. Armed with 3×2 152mm Type 43, 2×2 76mm/60 Type 98, 2×3 25mm/60 Type 96, 2×4 610mm TTsn 18 DCS, 2 Seaplanes.

Note shown here are a modification of this design, and there three alternative designs for the oyodo class.
Interestingly, the first two in 1938 were planned four twin 127mm/40 Type 89 DP-AA Guns.

Design C-44 Agano Kai (1941): “Kai” means “improved”. This was basically a modified Agano with 4 main turrets instead of 3 and better top speed with 7 ordered in 1941 to complete the replacement of the Nagara and Sendai class cruisers. Never built, due to other priorities.
Dimensions: 175 (pp) x 184 (wl) x 16,4 x 5,9 meters for 8.250tons (standard) 9.670tons (Full load)
Prop. 4 shafts GST 153.000 shp, 38 kts, RA 11.600 km (6.300 nm)
Armour: 20mm Deck, 55/60mm Belt (Mag./Mach.) and armed with just one more 152mm Type 43 turret, 4×2 76mm/60 DP, 3×3 25mm/60 Type 96 same TTs and 2 Seaplanes
These were the last light cruisers designed in Japan.

Heavy Cruiser Design C-46 Torpedo Modification Proposal (1942): The Ibuki class, hulls 300, 301 derived from the Suzuya, it was decided to propose a massive torpedo carrier upgrade, with 5 quintuple launchers (2 either side, one centreline, no aircraft).

AA Conversions and AA cruisers projects

Design C-45 (1942) was designed as an answer to the US Atlanta and British Dido class. They were pure Anti-Aircraft cruiser from the start, like the Akizuki class flotilla leaders with four ordered for each surface battle group. Basically enlarged Akizuki type (which were very large destroyers), including seaplane facilities. They could have looked like Aganos with the same excellent 10 cm DP main guns. Src
Dimensions: 172 (wl) x 15,8 x 5,7 m, disp. 5.800 tons St. 7.150 tons FL. 4 shafts GST 103.000 shp, 34 kts, RA 13.000 km (7.000 nm)
Armour: 50mm Deck, 50mm Belt. Armed like Akizuki but with 6×3 25mm/60 Type 96 AA guns and 100 DCs, 2 Seaplanes.

Tenryu CLAA Conversion 1: 1936 plans ti rebuilt the two Tenryu class light cruisers like the British C class: 4×2 127mm/40 Type 89 DP-AA guns, 4×3 25mm/60 Type 96 AA guns, 2×3 533mm Torpedo Tubes, 36x DCs.
Tenryu CLAA Conversion 2: 1938 revision but with 4×2 76mm/60 Type 98 DP, 4×3 25mm/60 AA, 2×3 533mm TTs, 36x DCs.
Kuma CLAA Conversion proposal: 1938 same idea applied to the Kuma class. 2×2 100mm/60 Type 98, 4×3 25mm/60 Type 96 AA, 4×2 533mm TTs, 36x DCs.
Oyodo CLAA Conversion proposal (1941-42): Before the latter was reconverted as a HQ ship, but while under completion. She was to be upgraded with an impressive array of 12x twin 10cm DP guns and plethora of 25 mm (6×3 25mm/60 Type 96 AA guns), retaining two quad TT banks as well, no aviation. But this was the armament of 3 Akizuki class and industry bottlenecks cancelled the project. Known as the “Japanese Atlanta”
IJN Suzuya AA Conversion Proposal (1942): When Mogami was in repair and conversion into an aviation cruiser it was proposed to convert the next Suzuya and Kumano as Anti-aircraft heavy cruisers. Again prevented by acute 12,7cm guns shortage and no dockyard capacity. They would have carry five twin 12,7cm DP-AA mounts in place of their former main guns turrets.
IJN Kumano AA Conversion Proposal (1942): Suzuya only received half the conversion but it was planned full for IJN Kumano. The main gun rangefinder was to be replaced by an high-angle one and new Machine-gun director towers for controlled AA fire. Never carried out.

Source: Eric Lacroix – Japanese Cruisers of the Pacific War via secretprojects

Japanese “Super Cruisers”

Design X Large Cruiser (1918)

Assimilated for some authors to “Light Battlecruiser”, revolution of an earlier 1915 design, in Yuzuru Hiraga archives. Four turrets instead of three with 12-in guns but smaller hull and same displacement. Dimensions: 199,64 (wl) x 18 x 6,06 m, displacement 11.000 tons, 4 shafts GST 135.000 shp Steam Turbines 36 kts, protected by 25 mm deck and 76 mm belt. The armament comprised four single 305mm/45 (12 in) Type 37 Cannons shielded, seven single 140mm/50 Type 3 Guns and four 76mm/40 Type 3 DP-AA Guns as well as six single hull-mounted 533mm Torpedo Tubes. See deviantart design.

“Chichibu Kadekuru” hypothetical Large Cruiser class (1937)

These were designed as “heavy armored cruisers” and not yet battleships. The name is from documentation and its US authors. Probably two to four could have been planned, as found in the USN intel reports in the late 1930s. They were to be rated as 12-15.000 tons ships capable of 30knots and with six 12 inches guns. It is possible they adopted the German Deutschland class configuration to cheat on treaties. See also. It emerged from combined erroneous informations fro the Japanese side after 1936, misinformation and perhaps some False information to convince the congress to vote new warships.
Based on this hypothetical design, wargames and extrapolations pushed for the adoption of larger heavy cruisers, and this eventually led to the Alaska class design.
When the latter was known by the Japanese, this in turn led to the design the B-65 class. Thus this voluntary Japanese “fake” strongly motivated the Alaskas, which turned real and obliged both Japan to upgrade the B64 and the Soviets to start their Stalingrad class. Src Src Src

About the B64/65

The B64 was a “cruiser killer” with a moderately size artillery, and debate still rages about her nature, battlecruiser or “large cruiser” as the Alaska class. She displaced 32,000/34,800 tonnes deeply loaded, measured 787ft 5in pp/802ft 6in oa x 89ft 3in wide, had 4 single reduction geared turbines and 8 boilers for ca 160,000 shp and 33 knots, protected “only” by a belt 7.5in, bulkheads, decks 5in, and armed at fist with 3×3 12.2 in, 16x 3.9in/65 AA and 12+ 25mm AA, 8 13.2mm AA, and 2×4 24 inch torpedo tubes. Externally she looked like a less stubby, narrow-waiste Yamato.
Design was started in 1939, test carried also started with the 12.2 in gun. The design was completed in 1941 but revised as the USS Alaska construction and specs confirmed. The armament was changed to 14.2in guns and approved in 1942 but none was laid down. Aircraft carriers soon had all priority.
The upgraded B65 with her heavy artillery to answer the latter certainly was not any longer a “cruiser”. I’m just sticking to Conway’s books definition here: She was a capital ship, thus, not relevant to this topic. More on her.

Some WoW impressions:

IJN Agano

“Yodo”, a what-if design. Like Shimanto and Takahashi, fictional design using the newly planned 6-in dual purpose guns. The latter are upscaled versions of Mogami and Ibuki, but Yodo is an enlarged Atago with a 6th turret and a 18 shells broadside.





Grampus class submersibles (1932-36)

Grampus class Submersibles (1936)

Minelaying Submersibles 1932-1945:

HMS Porpoise (prototype), HMS Grampus, Narwhal, Rorqual, Cachalot, Seal

WW2 British Submersibles:
X1 | Odin | Parthian | Rainbow | Thames | Swordfish | Porpoise/Grampus | Shark | Triton | U class | T class | S class | A class

The first British internwar minelaying submersibles: The 1,800-tons Grampus-class were derived in 1936-38 from the single prototype HMS Porpoise launched 1932. Five of a modified design were built therefore after years of testing and improvements. They shared the same marine mammals names, and paid a dearly price to world war two with just one surviving: HMS Porpoise was sunk by Japanese aircraft in 1945, Grampus by Italian torpedo boats in 1940, Narwhal by the Luftwaffe near Norway Cachalot by Italian TBs in 1941, and Seal was captured in the Kattegat…

HMS Porpoise Prototype

HMS Porpoise was long-derived from a German Coastal Minelayer UC-5 obtained as war reparation, scrapped in 1923. The numerous reports helped settting a working base that was later refined in 1929.
Eventually the final designs was approved and voted for contruction in 1930, attributed to Vickers Armstrong, Barrow, laid down in 1931. HMS Porpoise was launched on 30 August 1932.
As designed she was a saddle-tank type submersible for which Vickers just enlarged their existing Parthian class. The hull shape and internal arrangement was essentially the same, but of course with a provision in th ballast to fit the torpedo wells.
The deck gun 4.7in was replaced by a 4in/40 QF Mk XII in 1934. Mines were carried in the superstructure on an endless chain, which in general layout resembling that of the converted M3, but the excessively slow diving of the latter was avoided by careful design of the mine casing. Designed diving depth was 300ft and test depth 200ft, whilst the fuel was mainly in external welded tanks. In addition to the 50 mines of conventional type, 12 M2 mines could later be carried in place of the 12 torpedoes.

⚙ HMS Porpoise specifications

Displacement 1500t standard; 1768t/2053t normal
Dimensions 289ft oa x 29ft 10in x 15ft 103in mean normal load (88.09 x 9.09 x 4.84m)
Propulsion 2-shaft Admiralty diesels plus electric motors, 3300bhp/1630shp
Speed 15.Skts/8.75kts
Range Oil 155-190t
Test Depth Circa 300 ft (90 m)
Armament 6-2lin TT (12), 1x 4.7in/45 QF Mk IX, 50 mines
Crew 59

HMS Porpoise in Service: A remarkable career

HMS Porpoise was commissioned on 11 March 1933. Her early career is in research. In 1938 she had a new commander, George Walter Gillow Simpson, RN, from 21 September to the next 15 Nov 1939.
On 25 Aug 1939 she departed Portsmouth for Gibraltar to join the 1st Submarine Flotilla, but departed for Malta the following day. On 19 Sept. 1939 she was conducting exercises with HMS Otway (Cdr. H.R. Conway) off Malta with also HMS Cachalot (Lt.Cdr. S.W.F. Bennetts). On 11 October she was scheduled to return hom, via Gibraltar (15 Oct) and made it to Portsmouth 5 days later.

On the 24th, she departed for Sheernes and Chatham Dockyard for a refit. It was completed on 18 Jan 1940 and with a new commander, P.Q. Roberts, RN she returned from the yard to to Sheerness and after trials on the 21th, she returned to Portsmouth and after exercises, including conducted mine laying exercises off Portmouth on the 25th, on 7 Feb 1940 she proceeded to Yarmouth Roads, Isle of Wight followed by exercises off Yarmouth and returned to Portmouth, alternating between the two until 12 March 1940 when she departed Portsmouth escorted by HM yacht Sona, to cover the convoy FN.20 for Rosyth.
On 16 March 1940 she arrived there, and departed three days after for her 1st war patrol, escorting convoy ON 21 to Bergen and on the way back HN 21. She was back on 25 March and departed again on 27 March for her 2nd war patrol, escorting convoy ON 23 to Bergen and HN 23 back. Nothing happened for her during the trip.
On 13 April under Cdr. P.Q. Roberts she made her 3rd war patrol, relieving HMS Clyde off Egersund, Norway.
On the 16th at 21:36 she spotted the surfaced U-3 (Type IIA U-boat) and fired from 2000 yards six torpedoes at her, 10 nautical miles south-west of Egersund, but they all missed. U-3 manoeuvered towards her and fired one torpedo, passed overhead Porpoise as she was diving. Her 3rd war patrol ended on the 29th. After a maintenance and crew’s rest, she returned for her 4th patrol after exercizes on 8 May with HMS Tetrarch in the Firth of Forth. Her patrol started on 12 May, ordered to lay a minefield off Norway.

This minefield would later claim the German minesweeper M 5. She reported on 16 april firing on an U-Boat which disappeared and later was probably U-1, which hit a mine laid by HMS Narwhal.
On 15 May 1940, under command of P.Q. Roberts, she lays minefield FD 11 (48 mines) off Kalvag, Norway. It claimed the Swedish merchant Sonja (1828 GRT, built 1923) with a german prize crew.
On 9 June 1940 she left Immingham for her 5th war patrol and laid a minefield off Smøla, Norway. On the 12th she spotted a torpedo wake but was not hit.

On the 14th she laid minefield FD 18 (50 mines) off the Ramsoyfjord, Norway. It claimed on the 18th German minesweeper M 5 (682 tons). On the 19th while charging her batteries north of Halten she was attacked by the luftwaffe, took a bomb near-hit and made a crash dive to escape. On 4th july she made her 6th war patrol, and on the 9th was attacked by aircraft underway. On the 25th, she departed Immingham for her 7th war patrol, laying a minefield off the west coast of Denmark after patrolling off Lister, Norway. This was minefield FD 23 (50 mines with flooders set for 28 August 1940). She started her 8th patrol in August, 5, nothing to report. On 13 September, 9th patrol, she laid now under command of Lt.Cdr. J.G. Hopkins, the minefield FD 26 (48 mines) in the Bay of Biscay north-west of La Rochelle, France.
On 16 Sept. 1940 at 0047 hours, she spotted and launched six torpedoes on what was believed to be a surfaced U-boat south of the Penmarch peninsula, but more likely a trawler.
On 20 Sept. 1940 she was ordered to Falmouth and Holy Loch for her Passage north through the Irish Sea. After attack exercises in the Clyde area she departed for her 9th patrol in the Bay of Biscaye, but missed the only U-Boat signalled bound for Lorient.
On 30 Nov 1940 HMS Porpoise departed Holy Loch for Halifax in Canada. She departed Halifax for her 10th war patrol, escorting convoy HX 99 on 26 December. She was back on 13 Jan 1941. On the 26th she departed Halifax for her 11th war patrol, escorting convoy HX 105 home this time. She however soon departed Holy Loch back for Canada. On 7 March while underway she made a torpedo attack on a submarine, likely German U-boat U-A which was in the area at the time, but she missed. She escorted convoy SC 26 and later SC 29. On 20 May 1941 she sailed to Troon for a refit. It ended on 1st September. Later after post-refit trials she proceeded to gunnery and torpedo exercises with HMS La Capricieuse, and was sent to Govan’s No.2 dock for preparations for her Mediterranean service.

Mediterranean Service

From late 1941 to late 1942 HMS Porpoise operated in the Mediterranean:
Under command of Lt.Cdr. E.F. Pizey, DSC, she departed Holy Loch for Gibraltar, escorted in Irish Sea by HMS White Bear and later the German B-Dienst intercepted a signal giving her exact route, but failed to spot her. On 11 October she departed Gibraltar for Malta, unloading cargo and passengers and later more to Alexandria, including personal from Malta. Axis activity on the eastern Mediterranean was so fierce this was seen as a safer way than regular warship. In november she made two more trips between Malta and Alexandria. On 28 November 1941 she was based in Alexandria, departing for her 14th war patrol, and 1st in the Mediterranean, ordered to patrol the south-west approaches to the Anti-Kithera Channel in Greece.

On 9 December a few miles south of Navarino area where she patrolled newt, in the Peloponnese, she spotted, torpedoed and badly damaged the German passenger and cargo ship Sebastiano Veniero (Jansen), carrying 2,000 UK, South African and other Commonwealth POWs from Benghazi to Taranto, 300 being killed but the rest survived as the ship was beached at Methoni. The TB Centauro was escorting her. Later the destroyers Ascari and Carabiniere arrived and the hospital ship Arno to rescue more. Despite of this, on 11 December, she surfaced and fired two torpedoes at the beached wreck but made no hit. On the 17th, while passing north of Crete for home, at 13:11 hours, she sighted a German U-boat surfaceed, but it was out of range (this was U-652 en-route to the Dardanelles and black sea).

On 2 Jan 1942 she departed Alexandria for Haifa, embarked 12 dummy mines and laid this dummy minefield off the harbour as a test then on the she embarked 46 mines in her 15th war patrol, laying them off Suda Bay, Crete. It will claim on 14 Jan the German auxiliary vessel 11 V 1 (former Greek Palaskas) and on the 18th, she torpedoed the Italian merchant Città di Livorno (2471 GRT, 1930) 15 nm NE of Cape Maleka in Crete. On 7 February she departed Alexandria for her 2nd cargo trip to Malta and a third from 3 March. Experiencing engine problems she was docked in Alexandria on 31 March (Gabbari dock) until the 9th. She departed for Port Said and back. On 18 April she started her 4th trip to Malta.
On 2 May, 20:50 she sighted an ‘U-boat’ based on a report, but she was 50 miles behind her and ciuld not attack. She was in fact the Italian Nereide.
On 23 May this tume under orders of Lt. L.W.A. Bennington, DSC, she departed Alexandria for her 5th trip.

On 7 June, she departed Malta for her 16th war patrol and escorting convoy operations to Malta as part of Operation VIGOROUS. She also patrolled off the Gulf of Taranto.
On 15 Juned, 19:35 about 140 miles west of Crete she was attacked by aviation, had ner-missed by small bombs and dived to 60 feet. At 20:25 she was attacked again, and dived too, no damage.
On 1st July she was overhauled at Port Said. On she departed Haifa for her 17th war patrol and to lay a minefield off Ras el Tin, Libya, also patrolling Cyrenaica. One mine will later claim the Italian torpedo boat Generale Antonio Cantore.

Later, a westbound convoy with Albachiara (1245 GRT, built 1904) and Sibilla (1077 GRT, built 1900) escorted by the sub-chaser Selve crossed it, but the mines had not time to be armed. She tried to torpedo Sibilla but missed. However she later sank the Italian transport Ogaden (4553 GRT, built 1905) off Ras el Tin. She was transporting 200 POWs from Benghazi to Tobruk, escorted by Generale Carlo Montanari (another “Generali” vintage WW1 destroyer). MAS 561 came to pick up survivors but was soon chasing Porpoise.

On 15 August, she spotted, torpedoed and sank the Italian merchant Lerici (6070 GRT, built 1941), 120 nm north of Ras Amir while in convoy with Ravello (6142 GRT, built 1941) and escorted by the destroyer Nicoloso Da Recco and TBs Polluce, Calliope and Castore. Hit by two torpedoes she was abandoned. Polluce made three runs with 38 depth charges, claimed Porpoise sunk and returned to pick a survivor. Bersagliere and Mitragliere finished off the wreck by gunfire and rescued more survivors, but twenty-one were missing. on the 19th however she was off Tobruk detected and depth charged by the TB Lince escorting the transport Iseo (2366 GRT, built 1918) to Benghazi. She claim having damaged her, which was true. She stayed under until not hearing anything and surfaced to depart for home, escorting on her way on 20 August by Beaufighters in escort and later two Hunt-class destroyers. While she was in repairs in Port Said, one of her mines claimed Generale Antonio Cantore off Tobruk.
She departed Haifa for her 18th war patrol on 28 September, laying a minefield off Tobruk and proceed to Malta to unload cargo aboard. Once done on 10 October she was ordered to the Ionian Sea, with just four torpedoes aboard. On the 13th afternoon, she was informed of a convoy of two merchant ships proceeding from Brindisi to Benghazi but she missed the convoy which passed a little further east. She proceeded to Beirut next, and on the 29th departed to unload cargo to Malta. On 18 November she spotted an unidentified U-Boat about 3 miles away which was Pietro Micca on a transport mission to Tripoli. In fact the latter also spot her ahd stayed distant as ordered. The following day Porpoise spotted and fired a torpedo at the auxiliary patrol vessel F39/Fertilia off the Libyan coast but missed. However later that day she torpedoed and sank the Italian tanker Giulio Giordani (10,534 GRT, 1939) 45 nm NE of Misurata, Libya (she had been torpedoed and damaged earlier by British aircraft, abandoned). On the 21th she was ordered to return to Malta via Kerkenah and two days later, spotted, torpedoed and sank thesame Italian auxiliary patrol vessel F39/Fertilia she previously missed. On 4 December she left Malta for Gibraltar.

Pacific Service

On 14 Dec 1943 HMS Porpoise departed Gibraltar for Portsmouth. She conducted exercises off Portsmouth and transited to the Holy Loch. In February 1944 she trained in the Clyde area and alternated with Campbeltown. They went on until 17 Apr 1944, when she departed with Lt.Cdr. H.A.L. Marsham as new commander Holy Loch for Gibraltar. She was ordered for the Far East, assigned to the 4th Submarine Flotilla based at Trincomalee. She was escorted in the Irish Sea by HMS Telemachus and HMS Flint Castle. On 6 May she departed Gibraltar with HMS Telemachus and HMS Clyde for Malta, escorting underway convoy KMS 49. From there, she transited to Alexandria, Suez, Aden and on in June, Trincomanlee.
The Malacca Minefield
On 1st Jul 1944, she departed Trincomalee for her 20th war patrol and 1st in the Far East, ordered to lay mines in the Malacca Strait. She laid 30 mines (minefield ML 014) off the mouth of the Deli River, Sumatra, Netherlands East Indies. Her mines would claim Cha-8 (100 tons), the freighter Bukun Maru and Special Minelayer No.1 in March 1945.

Operation Rimau (attack on Singapore)
On 27 Jul 1944 she departed Trincomalee for Fremantle in Australia assigned to the 8th Submarine Flotilla. On the 11th she departed Fremantle for her 21th war patrol to conduct Special Operation Rimau, launching fifteen one-man submersible canoes (‘Sleeping Beauties’) against the naval base of Singapore. In all, she carried 96 passengers and crew members. The canoe were presumably carried inside the mine wells. 17/18 saw her passing Lombok Strait and on the 23th close to midnight she launched a folbot manned by Lt.Cdr. Donald Davidson, RNVR, and Corporal Clair Stewart in reconniasance of the island of Merapas usable as an advance base. The following day they were back confirming it was emtpy and safe as base. On the 28th, 13:59 HMS Porpoise captured the Malay junk “Mustika” later used for the operation, sneaking in with canoes aboard. The Malay crew was kept hostage in the submarine as the boarding party and the junk was in tow. On 29-30 September she transferred the Canoes to the Mustika and sailed away. This was a suicide mission as none of the 23 men which entered the harbor, apart three ships rumoured sunk they were all killed or executed by the Japanese.

The loss
Not waiting for the special operatives, she departed on 4 October for Lombok and returned to Fremantle. On the 30 she was sent back to Colombo, and later Trincomalee. She proceeded to various exercizes and on 2 December
under command of A/Lt.Cdr. H.B. Turner, departed Trincomalee for her 22th war patrol and to lay a minefield off Penang as well as patrolling the Nicobar Islands. The minefield ML 019 had 46 mines in two rows but claimed no victim. She ended her patrol and spent the rest of the year in Trincomanlee.

On 3 Jan 1945 she departed Trincomalee for her 23th war patrol, ordered to lay another minefield off Penang. Once done, she departed for a patrol while at 13 January, 01:01 hours, HMS Stygian received Captain S.4’s signal about the submarine being in trouble 17 miles northwest of Pulo Perak, via an Ultra decrypt. It established that on 11 January she had been attacked by a Nakajima B6N2 Tenzan heavy bomber from 331 Air Group based at Penang. One of the two closest 60kg bombs missed her port bow but the other was a direct hit. Unable to dive she was attacked again by another Tenzan at 11:45 off Perak Island while she managed to submerged but was leaking oil as reported by the Japanese. At 20:57 hours she had a third attack with six 60kg bombs falling and again at 10:00 hours the following morning. IJN aviators just had to follow the leaking oil tray.
HMS Stygian arrived and tried to contact Porpoise by radio, searched the area but found nothing. She sank at an unknown location with all hands: Her wreck had never been discovered yet. As sad end for probably one of the most succesful allied submarine of world war two.
Nevertheless, her minefield claimed on 15 January the Japanese auxiliary minesweeper Kyo Maru No.1, on 27 March the Japanese auxiliary minelayer Ma 1 and on 18 May the Japanese submarine chaser Ch 57.

The Grampus class

Usually assimilated with the Porpoise, but of a later, improved design, these five boats approached the double-hull type, with a pressure hull shaped to include the principal tuel tanks. They were laid down in 1933-36 and completed in 1936-39, while P411-P413, which would have differed io having a circular section pressure hull, ordered from Scotts on 13 January 1941 but cancelled in September. Stability was increased from that of Porpoise, as was the reserve of buoyancy, and armament was the same apart from the later addition of a 20mm gun in HMS Rorqual. Diving depth figures remained the same but fuel capacity was reduced. Grampus and Cachalot were sunk by Italian Torpedo Boats, Narwhal presumably by the Luftwaffe, Seal damaged by a mine before capture and integration in the Kriegsmarine (see later).

Author’s old illustration

⚙ Grampus specifications

Displacement 1520 standard; 1810t/2157t normal
Dimensions 293ft oa x 25ft 6in x 16ft 10in mean normal load (89.30 x 7.77 x 5.13m)
Propulsion 2-shaft Admiralty diesels plus electric motors, 3300bhp/1630shp
Speed 15.75kts/8.75kts.
Range Oil 119-147
Test Depth (tested, not max) Same as Porpoise
Armament Same
Crew Same

General assessment

As seen above, these were the only and last minelayers submarines deployed by the RN in WW2, and they were globally successful. Their large size guaranteed long range, and they were roomy enough to be used as cargos and carry special operations with teams and their equipments. HMS Porpoise was by far the most successful, perhaps of all British submarines of the war. The top ten (yet to document and create) often includes HMS Splendid (P228, 9 kills), HMS Upholder (U-class) sinking four Italian warships, and HMS Trident operating from a Soviet base which sank the Ostpreufen, Donau II, Bahia Laura, UJ-1213, damaged Levante (4769 GRT) and sunk UJ-1201. Both captains, Geoffrey Mainwaring Sladen and Malcolm david Wanklyn became “aces”, which was rare. The captain turnover was such that not many could stay in place. Also the practice of “aces” in submarines was more sketchy, and not well established in the RN. Was there a difference between trade ships and warships ?
Nevertheless, while combining three main theaters of operations from 1939 to 1945, and with the capacity of laying mines in addition to their torpedo and deck gun, the class had the potential to have the best kill/tonnage ratio.
HMS Porpoise based on this was certainly in that top ten, but her sad end was caused by her leaky fuel tanks, an issue detected and solved by the following Grampus class. She indeed combined direct hits with indirect ones through her minefields.
The Grampus class were less successful (see later).

Read More


Akermann, Paul (2002). Encyclopaedia of British Submarines 1901–1955 (reprint of the 1989 ed.). Penzance, Cornwall: Periscope Publishing. ISBN 1-904381-05-7.
Bagnasco, Erminio (1977). Submarines of World War Two. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-962-6.
Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
Chesneau, Roger, ed. (1980). Conway’s All the World’s Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press. ISBN 0-85177-146-7.
McCartney, Innes (2006). British Submarines 1939–1945. New Vanguard. Vol. 129. Oxford, UK: Osprey. ISBN 1-84603-007-2.
Caruana, Joseph (2012). “Emergency Victualling of Malta During WWII”. Warship International. LXIX (4): 357–364. ISSN 0043-0374.
Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
Frampton, Viktor & Domenico, Francesco de (2015). “Question 13/51: British Submarine Actions of WW II”. Warship International. LII (2): 116–118. ISSN 0043-0374.
Napier, Christopher (2017). HMS Rorqual: Commanded by Lennox Napier DSO DSC: June 1941–December 1943. Friends of the Royal Navy Submarine Museum.


No model kit found yet.


The Porpoise/Grampus class in action:

HMS Grampus

HMS Grampus (N56) was the lead ship of her class of mine-laying submarine of the Royal Navy. She was built at Chatham Dockyard and launched on 25 February 1936. She served in World War II off China before moving to the Mediterranean Sea. She was sunk with all hands by the Regia Marina on 16 June 1940.
On 16 June 1940, under the command of Lieutenant Commander C. A. Rowe, Grampus laid mines in the Syracuse and Augusta, Sicily area. She was seen by the Italian torpedo boat Circe, which was on anti-submarine patrol with Clio, Calliope, and Polluce. Within a very short time, Grampus was destroyed. Wreckage came to the surface along with air bubbles and oil. Polluce was credited with the kill. There were no survivors. Some sources give the date of this action as 24 June 1940. See the details on uboat.net

HMS Narwhal

HMS Narwhal short but well filled wartime career. In 1939 she spent her time conducting exercises off Portland. On 15 Nov 1939 under command of Lt.Cdr. E.R.J. Oddie, she departed Portsmouth for her 1st war patrol, ordered to proceed to Halifax while escorting convoy OA 36 in part. On 2 Dec 1939 she departed Halifax with her sister HMS Seal, proceeding back home while escorting convoy HXF 11.
On 14 Jan 1940 she conducted exercises in the Firth of Forth and soon after departed to escort a Convoy to Norway, Bergen, which was formed to carry back steel as HN8 on the 20th.
In February 1940 she escorted the largest convoy yet with 29 ships escorted by five destroyers and her. She escorted back from Bergen the back Convoy HN 10 and later the Convoy ON 11 to Bergen. Next were the convoys ON 12 and and ON 14. With HN 14, on 25 Feb 1940, she helped HMS Imogen and HMS Inglefield to sink U-63, south east of the Shetland Islands. After ON 17 she was back in exercizes in March, at Scapa Flow, notably direction finding trials.
On 13 Mar 1940 under command of Lt.Cdr. R.J. Burch, she was sent to Rosyth and assigned to operation R.3 (assistance to Finland by the occupation of Norwegian key points), her 7th war patrol. But this was curtailed by the Finnish armistice, the subs were recalled on 16 March. Bu she was bombed and had to dive escaping a Do 17 aircraft on the 17th.
In 1-5 April 1940 she departed Blyth for Immingham, embarking 50 mines as her 8th war patrol, laying a minefield in the Heligoland Bight (F.D.1).
On 10-17th for her 9th war patrol she laied minefield (F.D.5) off Skagen. It will claimed the German auxiliary minesweepers M 1302/Schwaben, M 1102/H.A.W. Möllerthe, Gnom 7, Kobold 1 and Kobold 3, the German minesweeper M 11, German auxiliary submarine chaser UJ D/Treff VIII, the armed trawler V 1109/Antares and Swedish merchant Haga.
On 1st May after laying the minefield F.D.6 (50 mines) in the Kattegat she attacked a German convoy, torpedoed/sank the troop transport Buenos Aires (6097 GRT, 1912) and torpedoed, damaged (constructive loss) the troopship Bahia Castillo.
Ships damaged by mines laid by Narwhal also included the armed trawler V 403/Deutschland, and the German merchant Togo (later converted as a fire direction ship) on May, 20, and Clara M. Russ. The auxiliary minesweeper M 1101/Fock, Hubert and merchant Palime were also damaged, beached but total losses. They were sunk by later minefields at Feistein Island/Bud, Jaerens, also in Norway (south of Stavanger) in June, Haugesund and kristiansund.
Narwhal may also have sunk U-1 noted in the Kriegsmarine as disappeared on patrol, on 6 April 1940, it is likely she ran into a minefield from Narwhal although Porpoise reported firing upon an unknown submarine, which may be her.

HMS Narwhal left Blyth on 22 July 1940 in what was her last war patrol. On the afternoon of 23 July, an aircraft reported attacking a submarine in her presumed area, believed by the Germans to be HMS Porpoise and assumed sank. Nevertheless, no new camed from Narwhal. She was presumed lost by unknown causes. In 2017, a Polish expedition in search of ORP Orzel found an unknown wreck, identified to be most likely HMS Narwhal, based on sonar data. On most publications she is reported “sunk, 30 July”.
See the details on uboat.net

HMS Rorqual

Far East Campaign

HMS Rorqual was Commissioned on 10 Feb 1937. She conducted her sea trials, and post-fixes in a dockyard before being assigned t the 4th sub squadron in the far east. Nothing is known about her early months in fall 1937 up to late 1939 (nearly two years), probably aletrnating between her Shanghai and Hong Kong station, ports visits and exercizes. On 6 September 1939 under command of Lt.Cdr R.H. Dewhurst, she conducted exercises off Singapore notably with HMS Grampus and on the 13th she departed for her 1st war patrol off Sabang. On 14 October she made her second in the Sunda Strait followed by exercises off Singapore in November. On the 7th, she was again patrolling off Sabang, until the 26th. On 5 December, she was in exercises with HMS Tenedos followed by a refit on the 20th, leaving on 13 April 1940 Singapore Navy Yard. After trials and fixes she departed on the 28 April forr Colombo and proceeded on orderes to the Mediterranean via Aden, Port Said and her first hole port of Alexandria (16 May) before departing for Malta.

Mediterranean Campaign

On 27 May 1940 HMS Rorqual laid a practice minefield off Malat, and was soon ready for her first wartime patrols in the Med. She multipled operations of minelaying, claiming the Italian merchant vessels Loasso, Celio, Leopardi, and Salpi, the water tankers Verde and Ticino and pilot vessel F 34/Rina Croce. But her more covered kills were the Italian torpedo boats Calipso, Fratelli Cairoli, Generale Antonio Chinotto, Altair and Aldebaran as the Italian auxiliary submarine chaser AS 99 Zuri and German troop transport Ankara. They also sank the former French merchant P.L.M. 24 and armed fishing vessel Coligny. By mines laid she also claimed damaged the Italian merchants Caffaro, Ischia and Carbonello A.

With her own torpedoes, Rorqual sank the Italian tanker Laura Corrado, submarine Pier Capponi, merchants Cilicia and Monstella, German tanker Wilhemsburg, ex-French merchant Nantaise. She also badly damaged the Italian auxiliary cruiser Piero Foscarin but missed and Italian submarine and the merchant Securitas. By Gunfire she sank two Greek sailing vessels, presubamy used by the Germans. By August 1940 she attacked an Italian convoy but missed with her spread the merchants Verace and Doris Ursino. She was chased off and depth charged by the Generale Achille Papa, but escaped.

In January 1941, HLS Rorqual attacked the tug Ursus and a floating battery dealt with with her single 4-inch gun surfaced at about 500 yards. The tug put up a firce response so Rorqual shifted fire to silenced her, before finishing off Ursus, until her fire became dadly accurate, forcing the submersible to dive. The only torpedo she fired had a gyro malfunction, returning straight at her ! She had to dive deeper to avoid it. But Ursus sank anyway as the battery, on fire, was evacuated but later towed to Dubrovnik.

Rorqual like her other sister ships was operfectly apt at carrying stores in her mine wells. On 19 January 1941 in fact she demonstrated this capability first: She loaded her cargo in Alexandria, and was the first doing this cargo trip to Malta. In all she would made five such runs to Malta in 1941. Later that year by June 1941 she fell under command of Lt. Lennox William Napier. She made more missions but with nothing notable, and a refit and more runs from Alexandria and in 1942 from Beirut, the British “magic carpet runs”. They notably carried avgas drum tanks (well suited for her mine wells) for the local Hurricane fighters and kerosene for cooking. Passengers were also carried in both ways. By October 1943 she carried from Beirut to Leros an entire battery of 40mm Bofors guns and their towing jeep to boot. The isolated island was indeed attack by the German air force.

Operations for 1943-44:
On 21 Nov 1943 after departing Beirut for hr last trip to Malta she was ordered to return to the U.K. for a refit and on 2 December under command now of Lt. G.S.C. Clarabut she transited at Gibraltar and escorted the convoy GUS-23 back home. Clarabut took command as Lt. Cdr. Napier was ill with jaundice and just now a passenger. On 11 December as she sailed, a German U-boat was reported in the Straits and this delayed her trip to the following day. On the 19th she met off Bishops Rock HMS Patti escorting her surfaced to Falmouth later in the evening.
On 20 December, she departed Falmouth for Portland escorted by Vichy French submarine chaser Chasseur 5. The following day she arrived in Portsmouth when Chasseur 5 suddenly capsized with 22 aboard and she picked up three survivors. While off Portsmouth she met the destroyer Blyskawica and started her refit at the Portsmouth Dockyard from 28 December to 6 August 1944.
Based in Yarmouth and proceding to the Holy Loch escorted by HMS Cutty Sark she started trials and training, notably in the Clyde area and at the torpedo firing range of Arrochar, noise trials at Loch Goil., mine detection) trials off Fairlie and attack exercises, radar drills off Campbeltown, D/G tials off Helensburgh and log calibration, engine trials in Loch Long.on 19 October she was docked in AFD 20, Holy Loch and 4 days later departed again for Gibraltar intended for the Far East. From March 1944 she was under command of Lt. John Philip Holroyde Oakley, DSC, RN.
She escorted underway convoy KMS-67 and arrived on 2 Nov 1944 to Gibraltar, proceeding to Malta, Port Said, Aden, Trincomalee in December arriving on the 14th.

Return to the Far East

HMS Rorqual started operations against the Japanese as part of the British Pacific Fleet (BPF), laying minefields which claimed three Japanese sailing craft, also blasting three coasters with gunfire, damaging a fourth one. This was all in the east Indies. For example on 22 January she laid 50 mines (minefield ML 026) in Nancowry Strait, NE of Port Blair, Andaman Islands.
Later this month she is ordered to conduct air/sea rescue duties in the Andaman Sea. On 18 March she departed Trincomanlee for her 32th war patrol off the West coast of Sumatra and conducting the special operations Meridian and Caprice. Notably on 2 April 1945 she sank two sailing vessels with demolition charges off the west coast of Sumatra. She sailed to Fremantle and on 30 April departed Fremantle for her 33th war patrol, laying a minefield of Batavia (10 May).
On 20 May she was back at Fremantle and on 3 June departed for home, the only surviving ship of the Grampus class. He trip via Trincomalee, Port Said, Gibraltar, Portsmouth was followed on 28 July by her placement in reserve, under nominal command of John Philip Holroyde Oakley up to that date. She was later sold off, BU off Cashmore, Newport from 17 March 1946.
More details on Uboat.net

HMS Cachalot

Cachalot entered service under command of Lt.Cdr. Sydney William Floyd Bennetts from 26 Aug 1937 (he stays her captain until 15 Jun 1940). In 1937-39 she was presumably in British waters (no logs). On 1st September 1939 she departed Britain for Malta. She conducted exercizes with notably HMS Porpoise and Otway, and later Sealion and Oswald. In October she returned home via Gibraltar.
On 29 Oct she departed Portsmouth for her 1st war patrol in the North Sea. He second patrol started on 11 November, escorting a convoy to Halifax, Canada. She trained there in Demeber with HMS Hunter and HMCS Restigouche. She escorted a large convoy back home from 29 December 1939 to 12 January 1940.

She had later a refit at Chatham Dockyard, and exercizes off Portsmouth in April. On 13 April she departed Blyth for Immingham to embark mines but collided at 21:25 off Whitby (rammed by accident) by the Italian merchant Beppe. She was sent for repairs to the Tyne, Devonport Dockyard and Sheerness. On 15 August now under command of Lt.Cdr. J.D. Luce, departed Rothesay for her 4th war patrol, 1st time in the Bay of Biscay, and she had to lay a minefield off the Gironde estuary. She torpedoed and sank German submarine U-51 on the 20th in the Bay of Biscay.
Her minefield would later claim in September the German auxiliary minesweeper M1604. On the 24th she spotted and attacked a submarine with torpedoes in the Bay of Biscay, which was almost certainly U-48 (KL Heinrich Bleichrodt), but missed.

She served from the Holy Loch in December. For her 7th war patrol she was sent off Punta Delgada in the Azores, as a German invasion of the Azores was feared at the time.
On 26 Jan 1941 she laid minefield FD 28 (50 mines) off Bud, Norway. On 5 February she departed Holy Loch for her 9th war patrol, and to lay a minefield off Norway, which happened to be signalled later as Vest Fjord (which claimled the Norwegian merchant Huldra). On 28 March, now under command of Lt. H.R.B. Newton, DSC, RN, she laid minefield FD 32 (50 mines) off the Gironde estuary. By late April she was ordered to Plymouth and from there to Gibraltar to commence Mediterranean operations.

She transited via Malta to Alexandria and Port Said and started a serie of storage trips to the beleaguered Malta. Cachalot left Malta on 26 July bound for Alexandria when at 2:00 on 30 July she was spotted by the Italian destroyer Generale Achille Papa, and she had to crash dive. When resurfacing she was attacked by her. While attempting to dive again her upper hatch jammed, and she was rammed. The crew had to scuttle and abandon her. Apart the Maltese steward all were picked up by the Italians. See the details on uboat.net

HMS Seal

After her commission, HMS Seal performed her sea trials at Dartmouth-Torbay and made a first successful deep dive on 1st June 1939 when leaning of the loss of HMS Thetis that same day. Many of the crew had friends in this boat. She perform her torpedo trials at Gosport.
On 4 August 1939, she sailed to the far east squadron (in Shanghai), joining HMS Grampus and Rorqual via Gibraltar, Malta and Suez, but as the war broke out she stayed at Aden. She immediatelt started a round of patrols watching Italian activity in the area, fearing some help to German submarines. Back home, she escorted a damaged destroyer in the Mediterranean before reaching the North Sea for her first war patrol near the Dogger Bank, attacked by the Luftwaffe. Her second patrol show her escorting a convoy escort to Halifax in a 14-day crossing. Next she was assigned to Elfin, Blyth, in Northumberland. She made more war patrols in the North Sea, as part of the Norwegian campaign, after relocation to Rosyth.

Norway Operations
By February 1940, HMS Seal received commandos aboard (a boarding party) intended for the German tanker Altmark (which resupplied Graf Spee and was last spotted in a Norwegian fjord -still neutral). But the show was stolen by HMS Cossak but Seal was later visited by an admirative Admiral Horton in Rosyth for the general state of the boat and crew. In April 1940 the invasion of Norway had the submersible ordered even close to the Norwegian coast. Captain Lonsdale decided to enter Stavanger fjord, to reach Stavanger harbour, guided by his new precision Asdic to avoid being grounded along the narrow way.
Once arrived, he spotted four merchant ships under neutral flags, requesting to attack, having the personal to launch a strike on a seaplane base and land a shore party to sabotage the railway. But this was refused by Horton to not create another displomatic incident after the capture of the Altmark. There was also a shallow-draft German naval craft which he declined to hit by torpedoes, so the disappointed crew had to make the dangerous trip back through the fjord and proceed to Rosyth. HMS Seal narrowly escaped a torpedo attack underway and also later rammed and scrapped by a merchant vessel.

Dry-docked at Chatham, HMS Seal as HMS Cachalot were repaired, completed at Blyth and she replaced Cachalot for minelaying missions, notably Operation DF 7, a dangerous minelaying in the Kattegat, preventing the kriegsmarine to pass through Denmark and Sweden. Captain Bethall at the head of the flotilla, failed to persuade Admiral Horton to send her due to the numerous hazards of the place and narrow shoals, making the large subersible rather cumbersome in these waters. This was partly due to the exploit of Seal, navigating with Asdic through Stavanger fjord.

The Suicide Skagerrak minelaying Mission
On 29 April 1940, Seal left Immingham with 50 mines and entered the Skagerrak, meeting HMS Narwhal leaving, having just scoring six hits with six torpedoes, a rare feat of markmanship. This no doubt pimped up the crew’s resolve. Seal was maintained at shallow depth, maintaining speed lopw to spare fuel. But at this low depht she was spotted by a German Heinkel He 115 on 4 May, at about 02:30. She had to dive to the bottom, circa 90 feet (27 m) after being slightly damaged by a bomb. Lonsdale later detected German anti-submarine trawlers looking for them as he reached his initial minefield area, and diverted to the secondary target area. Her started to lay down these at 09:00, completing it 45 minutes later.

Mission accomplished, Londsdale ordered to turnback and head for home, with the trawlers still overhead. He tried an evasive course using Asdic to detect the pauses made by the trawlers to listen. At 3:00 pm, he spotted nine MTBs heading from a different direction but is was still daylight, and the Kattegat was still too shallow, but he evaded detection by zig-zaging. At 18:00 hiowever as he started to surface after such a long underwater crossing, he unwillingly entered an uncharted minefield. His two hydroplanes caught a mine stay-cable. At 06:30 pm the attached mine attached itself ot his stern, and scraped until one of the detonators hit, trigerring the mine’s explosion: HMS Seal was severely damaged and started to flood in.

The crew’s miraculous escape
All watertight doors were quickly sealed, and miraculously all but two of the crew were still alive. Even those, trapped in the after end, later managed to make their way to the control room. The German ship apparently assumed her sunk or never heard the explosion and left the area. Emergency repairs were done and at 22:30 Londsdale ordered to surface at last.
At 10:30 pm as the boat was emerging her stern stayed stuck on the sea bed until the bow made sharp angle which made work inside impossible. Even air quality deteriorated much, and attempt was made to blow air into the rear trimming system and for the second attemptn the 11-ton drop keel was released. After using even more compressed air to blow the remaining tanks, this was still unsuccessful. The third attempt also failed while oxygen ran out.

At 01:10, Lonsdale called to prayer with his crew moving as far forward as they could to rebalance, many fainting in the process. The captainalso thought to use the Davis escape gear but it needed hours to escape while flooding was a risk. Engineers managed to open a salvage-blow for a 4th and final attempt which saw the diesels, pushed to the absolute limit, catching fire, soon dyring out due to the lack of oxygen. Batteries were also nearly empty while high pressure air was not exhausted. While all seemed lost for good, one engineer realised there was still one air pressure group left, reached and opened the valve, and all that were still aware at the time felt the boat raising again, and this time, the stern followed.

Seal eventually surfaced at 01:30 and immediately with their last strenght men present managed to open the hatch. Fresh air usehed inside, causing blinding headaches as the crew had been so deprive from oxygen for so long. But all ultimately survived. Lonsdale arrived on the bridge and started to scan the horizin, sighting land. He decided to make it for neutral Swedish waters. Confidential papers were thrown overboard as the cipher books, Asdics were destroyed and also thrown overboard. He sent a message to the Admiralty “Am making for the Swedish coast”. He would receive “Understood and agreed with. Best of luck”, “Safety of personnel would be your first consideration after destruction of the Asdics”. However after some well-needed rest and restoration, engineers started to reports the rudder was damaged beyond repair. Still the boat could go in reverse but the only working engine was barely in shape and soon died out, leaving the boat stranded.

At 02:30, Seal unfortunately, now surfaced and unable to dive or move again, was spotted and attacked by two German Arado Ar 196s and a Heinkel. Lonsdale stayed the bridge under fire using a Lewis gun, which jammed, then another, which jammed too. Considering all his option, Londsdale decided to surrender. He had the white messroom table-cloth quickly hoisted on the mast. Leutnant Schmidt of one of the Ar 196 landed alongside and asked in english the captain to swim to him for a parley. Lonsdale, aged 35, made it so, and shortly after the enterview, the chief petty officer swam to the other Arado that also landed. The crew waited as the armed trawler UJ-128 arrived at 06:30. The crew attemped to scuttle their boat, but failed as a German boarding party took the crew in custody. Although leaking and patrly flooded, the crew saw in horror their submarine being towed to Frederikshavn.

Under the svatiska: The short career of “UB”
They would learn after the war that their mine belt sank the German freighter Vogesen (4241 BRT) and three Swedish ships until 5 June. But their story ends there. They became POWs until the end of the war. As for their submarine, it was the only British sub in this war to be captured and reused by the Kriegsmarine. It was no long to realize its potential as a minelayer indeed, as there were none (yet) in the Kriegsmarine. She was simply named “UB”.
She had temporary repairs at Frederikshavn, then was towed to Kiel and was completely refurbished under supervision of Admiral Rolf Carls which saw her usefulness. Her insisted to have her operational at any cost. This was long, complicated and went on until the spring of 1941. UB made her sea trials and first dive under command of Fregattenkapitän Bruno Mahn, aged 52, a trusted veteran and oldest German submarine commander in this war.

The boat was naturally showcased propaganda exhibit and acted as training boat until by late 1942 Krupp was able to deliver the brand new tailored minelaying mechanical system. The boat made minelaying runs which revealed so many issues left to solve, with cost soaring sky high. Dönitz ultimately pull the plug. In mid-1943 he decided to retire her for good (the dedicated Type XB – A dedicated post on them is in writing). She was paid off, stripped and left in Kiel dockyard but later hit and sunk as Admiral Hipper. For all what she costed, the only gain retired from this all was the British contact pistol torpedo detonator judged of superior design and subsequentely adopted.
On 3 May 1945 UB was scuttled in Heikendorf Bay and her wreck demolished by explosives.

Fate of the crew:
The crew was interrogated by the Kriegsmarine (meaning in a fair way, not Gestapo methods). Officers and ratings were separated and sent to several POW camps until April 1945. The crew had been adopted by the village of Seal which sent considerable gift packages to the crew until then. Two managed to escape, Petty Officer Barnes in poland which later made contact with the Polish underground. They reached the Soviet border, but the latter shot Barnes dead while his companion Briggs was emprisoned into Butyrka prison in Moscow. Engineer Don “Tubby” Lister also managed to escape many times until confined in the Oflag IV-C, Colditz Castle, built on a rocky hilltop. Relocated by a ruse in an open camp, he escaped in late 1942 to Switzerland and later arrived home at last. The rest of the crew was mostly detained in Marine-lager Westertimke, well treated. By April 1945, the Allies were at Bremen, 15 nautical miles (28 km) away, and they were marched off to Lübeck. During the journey, the column came under attack from Allied Spitfires. For surrendering his boat Both Londsdale and Lt. Trevor Beet faced court-martial in 1946, but given testimonies and report of his conduct in the circumstances, he was honourably acquitted. Personal note here: This story is too good not to be made into a movie.

Hipper class cruisers (1937)

Hipper class cruisers (1937)

Germany (1937)
Hipper, Blücher, Prinz Eugen, Seydlitz, Lützow

KMS Hipper and her sister ships were the first and only heavy cruiser class ever built by Germany. They were enabled by the 1935 Anglo-German naval agreement and were intended still as commerce raiders and to screen for battleships, but cheating on tonnage. Wartime showed they never really found their place, between the sinking of Blücher by an antiquated Norwegian fortress to the largely failed raid attempt of Prinz Eugen and the few sorties made later from Norway. On the five planned as part of Plan Z, three were of a modified design. Oddly, Lützow, the last one, was sold to USSR during the ill-fated pact of 1939-41. #kriegsmarine #ww2 #germanynavy #hipperclass #admiralhipper #prinzeugen #seydlitz #lutzow #blucher #kistiansand

Origin of the design and development

Cruisers to rule them all: The first heavy cruisers of the Kriegsmarine were separated from their only possible ancestors by nearly 40 years, the last two Scharnhorst 1906 class armoured cruisers, which served Admiral Von Spee well. They had been succeeded only by “leichtes kreuzer”, Armed with 15 cm guns. Any study on this subject was impossible under the Reichsmarine, the Versailles treaty prohibiting anything but eight light cruisers, less than 6,000 tons standard. To be exact 10,000 tonnes which was corresponding to five pre-dreadnoughts, and the remainder for light cruisers, those too old to have been interned in Scapa, or given as war reparation.

Following the Emden, a 1920s schoolship derived from a 1916 design essentially, the “K” class formed the backbone of the German cruiser force, followed by the Leipzig class cruisers, replacing all five of the obsolescent Berlin class cruisers. There was at this juncture no plans fopr a heavy cruisers, which would certainly have passed the 7,000 tons treshold, albeit it was still possible to imagine a reduced version of the Deutschland class cruisers with 8-in guns instead of 11-in (28 cm).

However with the arrival of Hitler to power already in 1933, all these limitations were soon contested. Under the advice of Admiral Raeder, based on the experience of the latest light cruisers, a new ambitious program was set up with the same idea of individual superiority to compensate for numbers. Various options to work on a 7,000 tonnes design were envisioned, like fitting single 8-in guns under mask on the existing Leipzig or K class, since a triple 8-in turret barbette seemed impracticable on the envisioned design beam.

The Anglo-German treaty unlocks everything

The Anglo-German Treaty of 1935 however de facto overruled all remaining limitations officially, and gave the Kriegsmarine some leeway. It enabled the capacity to produce “Washington” cruisers (10,000 tons, eight 8-in guns), but not before 1943. This Agreement was signed on 18 June 1935 and essentially gave the Kriegsmarine 35% of the Royal Navy tonnage.
This fixed ratio on a permanent basis indeed completel overruled Versailles limitations, and despite the opposition of France (which was not consulted, as Italy), this agreement was registered in League of Nations Treaty Series on 12 July 1935, gaining de facto international recoignition. Despite its “generosity” the agreement still, was abrogated by Adolf Hitler on 28 April 1939.

In the context of “appeasement” before Munich it was a bold gesture from British diplomacy in order to reach better relations with the Reich. Therse were still conflicting expectations between the two countries. Germany saw it as a de facto Anglo-German alliance against France and the Soviet Union but Britain saw it as a new, perhaps more generous arms limitation agreement to stil cap German expansionism. It was controversial and disliked by Royal Navy officials as dangerously close to 50%, the ultimate limit in the old scheme stating that the RN should be at least as powerful of the next two largest fleets combined.

Being equal to the US after Washington, and close to Japan, albeit a war with Japan was far more likely than with the “colonials” both at the time and since, an alliance between Italy and Germany for example, still had to be dealt with. The 35:100 tonnage ratio allowed Germany anyway an entry into the Washinton treaty limitations, despite never signing it. Some in the RN estimated -rightly so- that Germany could in all appearances present a 35,000 tonnes design and cheat on its declaration (which it did for the Bismarck class), or a 10,000 tonnes cruiser in what we are interested for, and also cheat on the displacement. Cheating on artillery was more complicated as it was much easier to verify.

But there were also in the RN advocates of this treaty, such as Admiral Sir Ernle Chatfield, First Sea Lord in 1933-1938. What he wanted by admitting Germany in the Washington treaty, that the Kriegsmarine would be obliged to follow more precise standardised classification compared to Versailles, and discouraged “innovations” of the kind that led to the construction of the Deutschland class “pocket battleship”, something extremely dangerous for British trade. Chatfield was instrumental into starting by March 1932 and worked in the spring of 1933 to convince the staff and politicians about the “moral right to some relaxation of the treaty (of Versailles)”.

Reijiro Wakatsuki giving a speech at the London Naval Conference

In February 1932, the World Disarmament Conference started in Geneva and the German demand for Gleichberechtigung (“equality of armaments”) was put into balance against the French “Demande de sécurité” (“security”) about Part V of the Versailles treaty. The British tried to seek a compromise but enabling some leeway from Part V but to still to some limit not to threaten France. However these proposals were rejected by both. In September Germany eventually walked out of the conference. With the nazis close to power, Britain tried hard to convinced Germany back to Geneva by December and obtained from the general assembly a “theoretical equality of rights in a system which would provide security for all nations”. Germany agreed to return to the conference just before Hitler became Chancellor. More negociations would follow to determine the rearmament limits.
However when Germany restarted it’s U-Boat program in clear violation or art. V.

Part V of the Treaty of Versailles… is, for practical purposes, dead, and it would become a putrefying corpse which, if left unburied, would soon poison the political atmosphere of Europe. Moreover, if there is to be a funeral, it is clearly better to arrange it while Hitler is still in a mood to pay the undertakers for their services.

Later, it was still hoped as discussed in a secret meeting in December 1934 to choose to not let Germany rearm despite of treaties, once it was agreed not to wage war on Germany on this point alone, and continue to negociate for a return to the table of negociation to the disarmament negociation and United Nations. As negociations went on, this time after consuting Pierre Laval, France premier, the Hoouse of Commons made clear to be more worried about a German bombardment of London and oto negociate with Germany an air pact outlawing bombing. The acceptation prize was the naval card. It’s really the 21 May 1935 “peace speech” by Hitler in Berlin which formally offered to discuss a 35:100 naval ratio.

In June, Joachim von Ribbentrop went to London for the talks, held at the British Admiralty office, with Foreign Secretary Sir John Simon for the British delegation. After some arms twisting on Ribbentrop’s side, it was agreed that Germany would build up their tonnage levels to what Great Britain’s tonnage levels were in the various warship categories. The next weeks were used to fix technical issues.

It was finally completed and signed on the British side by Sir Samuel Hoare, Hitler being quite pleased in what he saw as a great success of diplomacy. Most in the Perliament thought it still maintained the naval supremavy of Britain above all else, and many also sensed that the Kriegsmarine would be more framed than ever by much more restricting regulations, leaving less room for cheating. In the end, naval experts believed the Kriegsmarine would reach this new tonnage limit by 1942 at best, and this was confirmed in the Plan Z schedule table. But this never happened, between labour shortage, many design and R&D issues, but overall budget priority given to the Luftwaffe and Wehrmacht above all else.

What is important in the end is that there was a hidden side to this agreement and Germany was willing to concede “one third of the Royal Navy except in cruisers, destroyers, and submarines”. Indeed the idea was only to abide to newly-found Washington limits in appearance only. For U-Boats, more were to be built, and for destroyers, larger ones than any British equivalents, the same would be reached for heavy cruisers, now the door was open to the Kriegsmarine. Iconically, unlike what happened to Washington’s signatories, Germany would have its heavy cruisers after the former.

That was a blessing in the sense they could start a design based on the lessons gained over time with all class that were built in France, Italy, Britain, the US and Japan since the 1920s.
Raeder was confident thus, to have “the world’s absolute best heavy cruiser” after two years: The treaty was signed in June 1935, a keel could be laid down at the end of the year and a first ship completed at the earnest in 1937. And the Kriegsmarine could legally acquire five of them: With 50,000 long tons (51,000 t) of heavy cruisers based on 10,000-ton unitary basis.

Therefore the new German cruisers of the Hipper class would just mockingly stick to the limits with indeed a “Washington” main (heavy) armament, but cramming as much secondary, torpedoes and AA guns as possible, but lying on tonnage by more than a safe margin:
At full load, in battle order, the Hipper, second sub-class (1940) were nearing 20,000 tons, so double the Washington’s treaty limits! Only the Des Moines Class in service by 1948 would met these. Despite of this, the armament, harder to conceal, stayed inside the limits. But between size and propulsion they incarnated a design meant to be the ultimate, long range commerce raiders, perfectly able to act with the future plan Z battleships.

KMS Admiral Hipper (Bundesarchiv)

Design Development

While prospective designs has been discussed and lossely sketched before 1935, Raeder and his staff discussed their options this summer of 1935. Russia on one hand announced its intention to produce 180 mm guns heavy cruisers, being a potential adversary and out of the Washington treaty. It was still maintained that France, not UK was the main foe and any new design could be compared to French standards. On this, the new propective “Schweren Kreuzer” (still unnamed at this point).

The new class needed to be at least equal to the French Algerie class design, or the Italian Zara class. The Hipper were in fact the first five Schwerer kreuzer of Plan Z. Altered, the group was split between the first two and later three sister-ships of the following “subclass” (often separated according to sources), Prinz Eugen. The latter was named in tribute to the defunct Austro-Hungarian fleet, and promoted as an “all austrian crew”. Seydlitz and Lützow were the last of them, but limited capacity meant they could only be Started in 1936-37, and were significantly larger and heavier.

Based on 1935 requirements and 1933-34 previous discussions, the final draft was ready, with a classic four twin 8-in (203mm) artillery, which was on the work since 1933, a capabiliy to act both for the battle fleet, and as commerce raider and have the protection level of the French cruiser Algerie. The best option for the machinery was to adopt a diesel-turbine system already proven on light cruisers. Also an emphasis was put on a strong dual purpose, antiaircraft and torpedo armament. The new C/34 guns tailored for the new class have quite a story, which is developed below in the armament section.

After the final plans were approved, both Admiral Hipper (Kreuzer H, or “Ersatz Hamburg” as she was replacing this old cruiser) and Blücher (“Kreuzer G”, or “Ersatz Berlin”) were ordered in November 1934, before even the official denunciation of Versailles or 1935 agreement, fiorbidding Germany to have cruisers with more than 150mm guns. KMS Prinz Eugen (“Kreuzer J”) was ordered in 1935, this tile on a revised design and new internal arrangement, much larger (and obviously cheating on tonnage already). KMS Seydlitz and Lützow (“Kreuzer K” and “Kreuzer L”) were like Prinz Eugen not even order to replace older cruisers, a semblance of legitimacy for the Bundestag to vote new ships. These later cruiser originally were planed as light cruisers with four triple 150mm turrets according to what was planned in USSR, but in 1937 this was revised and they obtained the same 8-in gun turrets. We will be back on these alternative designs and projects on the upcoming WW2 german cruiser’s main portal.

Upscaling and future Schwere Kreuzer

Yet still, German had amibitious plans for its next classes once Hitler abrogated the agreement in 1939, though with a width carefully restrained to fit the panama canal. Plan Z (which was formed in accordance to the 35% ratio) indeed included only these five heavy cruisers. The irony is that they were the only ones actually built (less the last two were never completed). No aircraft carrier was completed, only four of the ten battleships planned, no battlecruisers, only three of the fifteen “panzerschiffe” (the now older Deustchland class), and less than half the light cruisers, none of the 22 “scout cruisers” (spähkreuzer Type 1938), and so on.

So, what we know about future heavy cruisers of the Kriegsmarine ?
Despite the enthusiasm of some video games to create bogus classes, nothing was planned. The only cruisers that came close were “Panzerschiffe D” (laid down 14 February 1934, Work halted on 5 July 1934, broken up), and E (never built) or the twelve “P-class”. They were all a virtual repeat of the Deutschland based on a different armour scheme, same armament of two triple 28 cm guns, and alternated diesel and turbines engines. The whole P class was canceled on 27 July 1939 before any keel was laid down. They were be the object of dedicated articles in the future, probably 2024.

4×3 6-in alternative design for “Kreuzer K”

The “Roon” an alternative design for “Kreuzer K”

“Clausewitz” a prospective “Kreuzer M”, next class of Schwere Kreuzer for 1945+

So forget the “Mainz”, alternative “cruiser K” armed with triple 6-in guns developed on the basis of the Admiral Hipper-class, the “Roon” same idea, but looking like and upscaled Nurnberg, “Hindenburg” as a totally fictious follow-up with triple 8-in guns turrets, or “Clausewitz” and its 21 cm guns for commerce warfare. The “O” class (“siegfried”) was however a legitimate battlecruiser project, “ägir” being a variant, “Admiral Schröder” an alleged project of the 1920s with 305 mm guns (part of discussions leading to the Panzerschiffe).

Design of the class

KMS Admiral Hipper, ONI recoignition plate

Hull and general design

Master files on navsrc

The Hull shape was brand new. Flush deck, unlike previous light cruisers, the general outlook was based on the Leipzig, with bulges and an internal belt providing longitudinal strength. The initial design called for a straight stem with an overall length of 202.8m, on Hipper and Blücher. But after trials, the same constatations were made as for the Schanhorst class: Admiral Hipper was the first to have her bow reconstructed as a clipper clipper one. Blücher was completed with one, and the remaining cruisers were all completed with a reconstructed stem.
The superstructures were closer in design to the capital ships than light cruisers; There was, in order from bow to stern, the base superstructure, going from “Bruno” turret’s barbette, to “Carl” aft. This first level ran all along the ship and had cutout amidships to allow the torpedo tubes and secondary gun to have enough traverse for a 200° arc of fire.

Next, the conning tower, just high enough to see above “Bruno” roof. It was englobed in a larger “blockhaus” which aft part supported the first telemeter station, with wings. This structure was three-storey tall and secondary guns telemeters were located on either side as well as light FLAK.
Next was the main bridge structure. It was composed of two parts, the base part was rectangular but much smaller or bulky than for light cruisers. It supported the main bridge tower, made of a “0” section, and running for five storeys. On the original Hipper, the main navigation bridge mid-way to the top was open. During later refits and reconstruction it was enclosed. There was no secondary “admiral” bridge.
The very top comprised sets of binoculars and signal lamps. Two more telemeters were located there, one at the foot of the bridge tower, another on top, which was the main Fire control station (see later). Wing towers were secondary AA telemeters were installed under their bulbous caracteristic protection cap. The foremast, which was shorter, sat atop a platform aft of the tower, closely attached to it.