Keroman Submarine Base became a German U-boat base positioned in Lorient in the course of World War II. GroBadmiral Karl Donitz determined to construct the base on 28 June 1940. Between February 1941 and January 1942, 3 giant reinforced concrete systems were built on the Keroman peninsula. In 1944 work started out on a fourth shape. The base became able to sheltering thirty submarines below cover.
Although Lorient turned into heavily broken with the aid of Allied bombing raids, this naval base survived via to the end of the battle. Lorient changed into held till May 1945 via the Germans' Wehrmacht Heer ordinary military forces, although surrounded by using the American Army; the Germans refused to surrender. Since they couldn't wreck the bottom and its submarine pens, the Allies had decided to flatten the metropolis and port of Lorient to reduce the supply strains to the U-boat bases. Without resupply of fuel, weapons and provisions, it has become impossible for those U-boats to return to battle patrols in the Atlantic Ocean.