page_title: Imperial Japanese Navy in World War II
section_title: Aircraft carriers
hierarchical_section_title: Imperial Japanese Navy in World War II / Warships / Aircraft carriers
caption_attribution_description: 日本海軍航空母艦　翔鶴型「翔鶴」完成直後の写真。(Japanese Navy Aircraft Carrier Shokaku type "Shokaku" immediately after completion photo)
context_page_description: The Imperial Japanese Navy in World War II, at the beginning of the Pacific War in December 1941, was the third most powerful navy in the world, and the naval air service was one of the most potent air forces in the world. During the first six months of the war, the Imperial Japanese Navy enjoyed spectacular success inflicting heavy defeats on Allied forces, being undefeated in every battle. The attack on Pearl Harbor crippled the battleships of the US Pacific Fleet, while Allied navies were devastated during Japan's conquest of Southeast Asia. Japanese naval aircraft 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. After these successes, the Japanese now concentrated on the elimination and neutralization of strategic points from where the Allies could launch counteroffensives against Japan's conquests. However, at Coral Sea the Japanese were forced to abandon their attempts to isolate Australia while the defeat at Midway saw them forced on the defensive.
context_section_description: In the 1920s, the Kaga (originally laid down as a battleship) and a similar ship, the Akagi (originally laid down as a battlecruiser) were converted to aircraft carriers (航空母艦 Kōkūbokan) to satisfy the terms of the Washington Naval Treaty. From 1935–1938, Akagi and Kaga received extensive rebuilds to improve their aircraft handling capacity.
  Japan put particular emphasis on aircraft carriers. The Imperial Japanese Navy started the Pacific War with 10 aircraft carriers, the largest and most modern carrier fleet in the world at that time. There were seven American aircraft carriers at the beginning of hostilities, only three operating in the Pacific; and eight British aircraft carriers, of which a single one operated in the Indian Ocean. A large number of these Japanese carriers were of small size, however, in accordance with the limitations placed upon the Navy by the London and Washington Naval Conferences. Nonetheless the Japanese initially had the upper hand over the American and British, by grouping all of their fleet carriers into a single unit known as the 1st Air Fleet or Kidō Butai ("Mobile Force"). In the Kidō Butai, the two Shōkaku-class carriers were superior to any carrier in the world, until the wartime appearance of the American Essex class.
  Following the Battle of Midway, in which four Japanese fleet carriers were sunk, the IJN suddenly found itself short of fleet carriers (as well as trained aircrews), robbing them of a strategic offensive capability. The IJN consequently undertook an ambitious set of projects to convert commercial and military vessels into carriers, such as the Hiyō. Another conversion project, Shinano, was based on an incomplete Yamato-class super battleship and became the largest-displacement carrier of World War II. One exception was the Taihō, which was the only Japanese carrier with an armored flight deck and first to incorporate a closed hurricane bow. All three mid-war designs were sunk in 1944, with Shinano and Taihō being sunk by U.S. submarines, and Hiyō by air attacks. The IJN also attempted to build a number of fleet carriers called the Unryū-class, mostly based on the older Hiryū design rather than the newer Shōkaku or Taihō for the sake of reducing construction cost and time. Most carriers were still under construction or cancelled by the end of the war, while the few completed ships never embarked air groups due to severe shortages of carrier-qualified aircrew.
caption: The Shōkaku shortly after completion in August 1941
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