Befehlshaber der Unterseeboote

Befehlshaber der Unterseeboote (BdU) was the title of the supreme commander of the Kriegsmarines U-boat Arm (Ubootwaffe) during World War II. The term also referred to the Command HQ of the U-boat arm itself . The title was established on 17 October 1939, when Karl Dönitz was promoted to Rear Admiral (Konteradmiral). His previous title had been U-Boat Leader (Führer der Unterseeboote), a position he had held from January 1936.

On 31 January 1943 Dönitz was promoted to Grand Admiral (Großadmiral) and became supreme commander (Oberbefehlshaber der Kriegsmarine) of the entire Kriegsmarine, replacing Erich Raeder. He retained the title, but was replaced as operational commander at BdU by his chief of staff Eberhard Godt.

Godt's successor was Admiral Hans Georg von Friedeburg who held the position at the end of the war.

...
Wikipedia