Raeder served as chief of staff to the commander of the German cruiser fleet in World War I and was promoted to rear admiral in 1922 and to vice admiral three years later. Appointed naval commander in chief in 1928, he advocated the construction of submarines—forbidden by the Versailles Treaty—and fast cruisers to satisfy German naval needs. Made grand admiral during World War II, he was the first to suggest a German invasion of Norway, and he supervised the subsequent planning and execution of the invasion of Denmark and Norway (1940). He also urged—without success—the transference of the major theatre of war to the Mediterranean as an alternative to invasions of Great Britain and the Soviet Union, strategies he considered ill-advised. His many strategic differences with Germany's Führer, Adolf Hitler, who generally undervalued the role of sea power, ultimately led to his removal from the supreme naval command (January 1943). In 1946 he was sentenced to life imprisonment by the International Military Tribunal at Nürnberg (Nürnberg trials) but was released because of ill health in 1955.