Much of Vian's World War II service was in the Mediterranean, where he commanded a cruiser squadron, defended several critical convoys and led naval support at the Allied invasions of Sicily and Italy. His wartime service was completed in command of the air component of the British Pacific Fleet, with successful actions against the Japanese in Sumatra and the western Pacific. Post-war, Vian served in the United Kingdom, as a Fifth Sea Lord and as Commander-in-Chief, Home Fleet. He retired in 1952 with the rank of Admiral of the Fleet, took up commercial directorships and died at home, in 1968.