The Germans chose Bremen as the site of a bunker for the manufacture of three modules of the new Type XXI uboat.
The Type XXI comprised nine modules in all. The idea was to manufacture these at different sites and then bring them all together at an assembly plant. Bremen would make modules 3, 5 and 6 and these would then be transported by barge, 25 km. down the Weser, to the assembly plant at Farge.
Construction of the bunker began early in 1941; it was still unfinished at the end of March, when it was attacked by American bombers, which delivered several direct hits. The bunker did not become operational before the liberation and today is the foundation for an office building.
To protect the bunker’s workers, and those from the nearby Vulkan shipyard, the Germans built four protective bunkers: two Type T750s and two Type LSB1400s. Three of these remain; the one closest to the ‘Hornisse’ was demolished soon after the War.