After various surface ship commands and shore appointments, he took over command of the Pacific Fleet in 1941 following the Japanese attack on Pearl Harbor. From his Hawaii headquarters, he deployed his forces to win the Battle of Midway, and subsequently supervised the moves in the Pacific Campaigns, leading to successful actions off Guadalcanal and in the Leyte Gulf. To a large extent he was responsible for making the Pacific Fleet, weakened by Pearl Harbor, the instrument of Japan’s defeat. After the war he was briefly chief of naval operations.