The Atlantic Wall

The Atlantic Wall was a massive system of coastal fortifications built by Germany during World War II, along the western coast of Europe, to defend against an anticipated Allied invasion from Britain. It was built between 1942 and 1944 by Organization Todt, stretching from Norway through Denmark down to to the Spanish border but strenght was very unequal and far from the propaganda. It’s first role was to prevent or delay an Allied amphibious invasion but after a thorough inspection from Field Marshal Erwin Rommel it was repurposed to stop the allies right at the beaches and massively reinforced in 1943-44, not with new large naval guns, but many new standardized Concrete bunkers (the article reviews them all), new gun emplacements, new pillboxes (some with tanks turrets), machine-gun nests, tank traps, mines and barbed wire, flooded fields and anti-glider poles inland among others while inland millions of mines, many made in glass or wood to defeat magnetic detectors, were laid, while panzerdivisions were waiting an order to counterattack.
But the great test came in Normandy, and at D-Day despite all the propaganda the Atlantikwall only held for a few hours.
This is going with a complete new section on German naval fortifications since 1870.

See the article