Before the war Turner was with the War Plans Division (Navy) and involved in negotiations with the Japanese. In July 1942 he was posted as Commander of the South Pacific Amphibious Force (TF62) although he had never before been in active combat. He was chosen as an expert in amphibious operations, which were vital in the Pacific, and was to command transport, escort and bombardment forces. Turner’s first operation was the 7 August 1942 landing of 11,000 troops at Guadalcanal. In the aftermath of the landing, Turner was caught completely by surprise by the fleet of Admiral MIKAWA and in the Battle of Savo Island which followed, suffered a humiliating defeat.
Turner was then stricken with malaria, but returned to the scene to oversee the invasion of New Georgia. On 3 November 1943 he directed the landings in the Gilbert Islands in which the Americans suffered the worst casualties of the war up to this point. In 1944 he was transferred to the Central Pacific Area under SPRUANCE, and took part in the Marshall Islands operations. In the first of these, on Kwajalein, Turner took the Japanese completely by surprise. He was subsequently made a ViceAdmiral. On 16 and 17 February, while Spruance attacked Truk, Turner landed 8000 men at Eniwetok and the island was taken in four days. Turner landed the 2nd and 4th Marine Divisions on the Marianas, in June 1944.
In August 1944 Turner was assigned to set up an air base on Saipan which was to be used by B-29s bombing the Philippines in preparation for landings there. In February 1945 he led the expeditionary force which took Iwo Jima.