Fleet Admiral Chester William Nimitz, GCB, USN, was a five-star admiral of the United States Navy. He held the dual command of Commander in Chief, United States Pacific Fleet, for U.S. naval forces and Commander in Chief, Pacific Ocean Areas, for U.S. and Allied air, land, and sea forces during World War II. He was the leading U.S. Navy authority on submarines, as well as Chief of the Navy's Bureau of Navigation in 1939. He served as Chief of Naval Operations from 1945 until 1947. He was the United States' last surviving Fleet Admiral.