Admiral Karl Donitz was the German commander of the U-Boats and the German Navy. He planned the U-Boat wolf pack attacks on allied shipping, which nearly cutoff all supplies to Great Britain. In response, the allies instituted convoys and air cover to protect shipping. As the war dragged on, the allies inflicted a tremendous amount of damage and casualties to the German submarines, a loss from which Donitz could not recover. Near the end of the war, Hitler named Donitz as his successor, and he became the leader of Germany on Hitler's death. He was tried at the Nuremberg Trials and sentenced to ten years in prison. He died in 1980.