During the Second World War, the German navy will build five submarine bases on the French Atlantic coast in Brest, Lorient, St. Nazaire, La Pallice and Bordeaux. These 5 bases will have in 1943 the capacity to put 98 U-Boote to the shelter, of which 30 for the only port of Lorient. Being at the time of the war the main base used by the German submarines of which 203 will make a stop there, it is there that the most immense yards of protection of the U-Boote were born. This guide, illustrated by more than 100 photos and plans, invites you to discover in detail the construction and operation of these gigantic submarine bases in Lorient. You will also know the allied attempts to destroy them and the actions carried out by the French Resistance of the arsenal. You will discover the amazing projects that could not be realized and the role of the bases during the Lorient Pocket. This guide will finally explain their reuse by the French Navy for fifty years and their current reconversion for a peaceful purpose ... An indispensable guide for all fans of the Battle of the Atlantic, submarines, fortifications or the history of the port of Lorient.