Doenitz was a German naval officer and creator of Germany's World War II U-boat fleet. In January 1943, he was called to replace Admiral Erich Raeder as commander in chief of the German army, and appointed Großadmiral. In April 1945, shortly before the collapse of the Nazi regime, Hitler appointed Doenitz head of the northern military and civil command, then named Doenitz his successor as president of the Reich, minister of war, and supreme commander of the armed forces.