very different admirals: Raymond Spruance and William "Bull" Halsey. Spruance was calculating and cautious, while Halsey was more aggressive and known for taking risks. Most higher-ranking officers preferred to serve under Spruance; most common sailors were proud to serve under Halsey. Their commander was Admiral Chester Nimitz who was responsible for all Pacific Ocean assets. When the force was part of Admiral Spruance's Fifth Fleet, the carrier task force was commanded by Mitscher and bore the designation Task Force (TF) 58. When led by Admiral Halsey as part of the Third Fleet, the carrier force was commanded by Vice Admiral John S. McCain Sr. and its designation was Task Force (TF) 38. Planning for upcoming operations was 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. World War II The Fast Carrier Task Force took part in all the US Navy's battles in the Pacific during the last two years of the war. The task groups could operate independently or combine with the others as needs dictated. Raids against island strong points such as Iwo Jima or Chichi Jima might be undertaken by one or two task groups, but when a major operation was underway the task force would concentrate all four groups together. Each group would remain distinct but operate in close proximity to the other groups to provide the task force with maximum protection and maximum striking power. The Fast Carrier Task Force worked in conjunction with the other two major components of the Pacific Fleet: the Amphibious Force, which was much larger overall and which carried and provided direct support to the Marine forces, and the Service Squadrons of hundreds of support vessels which resupplied and maintained the fleet. The fleet and task group designation changed when the command of the fleet changed hands. When under the umbrella of Fifth Fleet, the invasion force was called the Fifth Amphibious Force. When Halsey had command of the fleet, Third Amphibious Force was the designation. By the time of the Battle of Iwo Jima in early 1945, the Task Force included eighteen aircraft carriers, eight battleships and two Alaska-class large cruisers, along with numerous cruisers and destroyers. TF 58 alone commanded more firepower than any navy in history. The