The Fast Carrier Task Force (TF 38 when assigned to Third Fleet, TF 58 when assigned to Fifth Fleet), was the main striking force of the United States Navy in the Pacific War from January 1944 through the end of the war in August 1945. The task force was made up of several separate task groups, each typically built around three to four aircraft carriers and their supporting vessels. The support vessels were screening destroyers, cruisers, and the newly built fast battleships. Carrier-based naval warfare With the arrival of the fleet carriers the primary striking power of the navy was no longer in its battleship force, but with the aircraft that could be brought to battle by the carriers. The means by which the US Navy operated these carriers was developed principally by Admiral Marc Mitscher. Mitscher determined that the best defense for a carrier was its own air groups, and that carriers were more easily defended if they operated together in groups, with supporting ships along with them to aid in air defense, anti-submarine defense, and rescue of downed airmen. Said Mitscher: "The ideal composition of a fast-carrier task force is four carriers, six to eight support vessels and not less than 18 destroyers, preferably 24. More than four carriers in a task group cannot be advantageously used due to the amount of air room required. Less than four carriers requires an uneconomical use of support ships and screening vessels." The ships of each task group sailed in a circle formation centered on the carriers. The supporting ships sailed relatively close by, and added their anti-aircraft fire to that of the carriers to help ward off attacking aircraft. When under attack by torpedo aircraft, the task group would turn toward the oncoming aircraft to limit attack angles. Other than this measure, the carriers in the task group would not take evasive action from their attackers. This was in marked contrast with the Imperial Japanese Navy, but the choice made for more stable platforms for the anti-aircraft fire of all the ships in the task group and allowed the ships in the group to sail more closely together. The primary defense of the group against air attack was the group's own fighter cover. Admirals The individual primarily responsible for the development and operations of the task force was Admiral Mitscher. The overall command of the task force alternated between two