The Fast Carrier Task Force was the main striking force of the United States Navy in the Pacific Ocean theatre of World War II. The Fast Carrier Task Force was known under two designations: when under the command of Admiral William Halsey it was designated Task Force 38. When commanded by Admiral Raymond Spruance the designation became Task Force 58. Planning for the upcoming operations were completed when each admiral and his staff rotated out of active command. This allowed the Navy to perform at a higher operational tempo, while giving the Japanese the general impression of naval assets greater than what were actually available.
The fleet designation also changed with each command change, with Third Fleet being the designation used for the fleet when under the command of Halsey, and the Fifth Fleet being used when Spruance held command. By the time of the Battle of Iwo Jima in early 1945, the FCTF included eighteen aircraft carriers, eight battleships and two battlecruisers, along with innumerable cruisers and destroyers. Task Force 58 alone commanded more firepower than any navy in history.
TF 38 came into existence in August 1943, built around USS Saratoga, and under the command of Rear Admiral Frederick Sherman. TF 58 was created on 6 January 1944 with Rear Admiral Marc Mitscher commanding, serving under the fleet command of Admiral Spruance in the Fifth Fleet. TF 38 continued to exist, but as a command structure only.
On 26 August 1944, Fifth Fleet changed designation to the Third Fleet, and TF 58 likewise became TF 38. Mitscher retained command of the Task Force, under the fleet command of Admiral William "Bull" Halsey, Jr. The force grew to nine CVs and eight CVLs in preparation for the landings on Leyte. Among the task groups of TF 38 on this occasion was Task Group 38.4, under the command of Rear Admiral Davison. Rear Admiral Davison's administrative assignment was as Commander Carrier Division Two.
Following the Battle of Leyte Gulf, Mitscher went on shore leave and planning duty, and Vice Admiral John S. McCain, Sr. took over as commanding officer of TF 38, which continued under Halsey and the Third Fleet.
On 26 January 1945, Halsey and McCain went on shore leave and planning duty, and Spruance and Mitscher returned to their previous commands. Third Fleet became Fifth Fleet, and TF 38 became TF 58.
On 28 May 1945, fleet designations and command personnel changed again, as Halsey and McCain returned to sea duty, and Spruance and Mitscher went ashore. Fifth Fleet became Third Fleet, and TF 58 became TF 38. This command arrangement lasted until the Japanese surrender ended the war on 2 September 1945.