First Air Fleet's operational component. At the start of the war, three carrier divisions made up the Kido Butai. Unlike in the United States Navy where carrier divisions served only in an administrative capacity, the carrier divisions of the Kido Butai were operational entities. The two carriers in a division fought together, often exchanging aircraft squadrons and commanders on strikes. The commander of the Kido Butai could wield the aircraft of its three divisions as a single entity bringing masses of aircraft crewed by highly trained aviators onto a single target. During the first six months of the war Japanese naval air power achieved spectacular success and spearheaded offensive operations against Allied forces. On 7 December 1941, the IJN's Kido Butai attacked Pearl Harbor, crippling the U.S Pacific Fleet by destroying over 188 aircraft at the cost of 29 aircraft. On 10 December, Japanese naval land based bombers operating from bases in Indochina, were also responsible for the sinkings of HMS Prince of Wales and HMS Repulse which was the first time that capital ships were sunk by aerial attack while underway. In April 1942, the Indian Ocean raid drove the Royal Navy from South East Asia. There were also air raids carried out on the Philippines and Darwin in northern Australia. In these battles, the Japanese veterans of the Chinese war did well against inexperienced Allied pilots flying obsolete aircraft. However, their advantage did not last. In the Battle of the Coral Sea, the Battle of Midway, and again in the Guadalcanal Campaign, the Japanese lost many veteran pilots. Because the Japanese pilot training program was unable to increase its production rate, those veterans could not be replaced. Meanwhile, the American pilot training program went from strength to strength. The American aircraft industry rapidly increased production rates of new designs that rendered their Japanese opponents obsolescent. Examination of crashed or captured Japanese aircraft revealed that they achieved their superior range and maneuverability by doing without cockpit armor and self-sealing fuel tanks. Flight tests showed that they lost maneuverability at high speeds. American pilots were trained to take advantage of these weaknesses. The outdated Japanese aircraft and poorly trained pilots suffered great losses in any air combat for the rest of the war, particularly in the Battle of the Philippine Sea. In the Battle of Leyte Gulf a few months later, the First Air Fleet was used only as a