When World War II broke out, he was serving as chief of staff, Amphibious Force, Atlantic Fleet (later redesignated Amphibious Corps, Atlantic Fleet). In September 1942, he joined the Amphibious Corps, Pacific Fleet, in San Diego, California, as chief of staff, and performed duty in Alaska in July and August 1943 during the planning and training phase of the assault on Attu and Kiska in the Aleutians. Immediately after this, he assumed duty as chief of staff of the V Amphibious Corps and embarked for the Pacific area. Overseas, he was promoted to brigadier general in November 1943 (with rank from September 1942), and was assigned additional duty as deputy commander, V Amphibious Corps. For exceptionally meritorious service during the assault and capture of Kwajalein, Saipan, and Tinian, he received two awards of the Legion of Merit, both with combat "V". He also performed additional duties during the Marianas campaign as Chief of Staff of East Marine Force, Pacific.