During 1943 and into 1944, Rear Admiral Giffen commanded battleship and cruiser task forces in the Pacific, participating in the latter stages of the fight for Guadalcanal (and was the losing commander in the Battle of Rennell Island), the Aleutians campaign, the invasions of the Gilbert and Marshall Islands, and raids against Japanese bases in the central Pacific. In May 1944, with the rank of vice admiral, he became Commandant of the Tenth Naval District and Commander, Caribbean Sea Frontier, with headquarters at San Juan, Puerto Rico from 14 May 1944 until 20 August 1945.