Grand Admiral, German Navy, during World War II. Entering the Imperial German Navy in 1910, he served in submarines during the First World War, rising rapidly in rank for his aggressive abilities. Between the wars, he was a strong advocate of submarine warfare, and when Hitler came to power in 1933, he was placed in charge of the German Submarine Fleet. He was promoted to Admiral in 1939. In 1943, he replaced Admiral Raeder as head of the German Navy, with the promotion to Grand Admiral (equivalent to the rank of Field Marshal). On 1 May 1945, after Hitler committed suicide, he became the only other person to have the title "Fuerher," having been named by Hitler to succeed him. He was in command for a short time before surrendering Germany to the Allies on 7 May 1945. He personally surrendered to the British on 23 May 1945. In 1945, he was convicted at the Nurnburg War Crimes Tribunal for "planning aggressive war," and sentenced to ten years in prison. His cooperation with the allied forces garnered enough favor to limit his time in Spandau prison to ten years. Many believed him to be innocent, including US Navy Admiral Chester Nimitz.