The post of Führer der U-Boote (FdU) ("Leader of the U-boats") was the senior commanding officer of the submarine service in the pre-World War II German Kriegsmarine, and the title of several senior commands during the war. From January 1936 and until 17 October 1939, Karl Dönitz served in this position. Thereupon Dönitz was named Befehlshaber der U-Boote (BdU) ("Commander of the U-boats"), and two subordinate FdU posts were established, FdU West ("FdU West") and FdU Ost ("FdU East"). In the further course of the war, several further posts were created: