The massive U-boat bunkers that sheltered Hitler's submarine fleet from enemy bombs in World War II dominated the countryside like medieval fortresses. Allied attacks on these bunkers succeeded only in reducing the surrounding towns to rubble while leaving the U-boats untouched. After the war, however, the Allies leveled most of these disturbing reminders of the U-boat menace. This is the first comprehensive study of the fabled submarine bunkers available in English. Drawing on archives and museums in Germany and England, U-boat historian Jak Mallmann Showell provides a description of U-boat bunkers from Bergen to Bordeaux and includes a history of each site and the flotillas assigned to them. Cutting through decades of confusion surrounding their construction, he also offers a thorough discussion of the building of this impressive engineering feat.