Type XXI submarine

The Type XXI was a class of diesel-electric U-boats built for the German Kriegsmarine from 1943 to 1945, and the first submarines designed to operate mainly submerged rather than on the surface. A streamlined hull and conning tower and a battery bank roughly three times that of the Type VII let a boat travel submerged at about five knots for some 75 hours, and a snorkel allowed the batteries to be recharged in under five hours. The boats were assembled from prefabricated hull sections made across Germany and joined at three yards, Blohm and Voss in Hamburg, AG Weser of the Deschimag combine in Bremen and Schichau in Danzig. Poor quality of the sections and Allied bombing delayed deliveries, and bombing brought the Deschimag yard at Bremen to a virtual standstill in early 1945.