page_title: Imperial Japanese Navy Air Service
section_title: Carrier aviation
hierarchical_section_title: Imperial Japanese Navy Air Service / Interwar development / Carrier aviation
caption_attribution_description: English: Mitsubishi B1M 日本語: 十三式艦上攻撃機。横須賀海軍航空隊所属。
context_page_description: The Imperial Japanese Navy Air Service was the air arm of the Imperial Japanese Navy. The organization was responsible for the operation of naval aircraft and the conduct of aerial warfare in the Pacific War.
  The Japanese military acquired their first aircraft in 1910 and followed the development of air combat during World War I with great interest. They initially procured European aircraft but quickly built their own and launched themselves onto an ambitious aircraft carrier building program. They launched the world's first purpose-built aircraft carrier, Hōshō, in 1922. Afterwards they embarked on a conversion program of several excess battlecruisers and battleships into aircraft carriers. The IJN Air Service had the mission of national air defence, deep strike, naval warfare, and so forth. It retained this mission to the end.
  The Japanese pilot training program was very selective and rigorous, producing a high-quality and long-serving pilot corps, who were very successful in the air during the early part of World War II in the Pacific.
context_section_description: Japanese interest in the potential of carrier operations demonstrated by the observations on board Furious led to the inclusion of an aircraft carrier in the eight-eight fleet program of 1918. The 7,470-ton Hōshō was laid down in December 1919 at Yokohama. Hōshō was the second warship after the British Hermes to be designed from the keel up as an aircraft carrier and the first one to be completed as from the keel up.
  In the 1920s, the larger percentage of aircraft that were initially acquired and inducted into service, were land based seaplanes whose main tasks were reconnaissance and anti-submarine patrols. The Japanese had drawn up plans for the formation of 17 squadrons of these aircraft, but budgetary constraints limited the units to eleven until 1931. Under the terms of the Washington Naval Treaty two incomplete capital ships were allowed to be rebuilt as carriers, for the Japanese; Akagi and Amagi. However, Amagi was damaged during the Great Kanto earthquake in 1923 and Kaga became a replacement. Akagi was completed in 1927 while Kaga completed a year later. With these two carriers much of Imperial Japanese Navy's doctrines and operating procedures were established.
  When Hōshō was completed, there was little thought was given to naval aircraft in an offensive role and moreover with only one carrier there was insufficient consideration given to carrier doctrine within the Japanese naval establishment. However, in 1928 the First Carrier Division was formed with three carriers and the study of the role of aircraft carriers in a naval engagement was initiated. Because of the short range of carrier aircraft at the time, many in the naval hierarchy were still very much surface oriented. They viewed carrier aircraft to be employed as support for the main battle fleet and not as offensive weapons. Aircraft were to act as scouts and spotters, layers of smoke screens for naval gunfire, fleet air defense, and later (with the increase in aircraft performance) as a means to attack battleships and other surface targets.
  Naval aviators however, had a different perspective, believing that a major aerial engagement to clear the space over the opposing fleets would precede the final surface battle, increasingly considered the enemy's carriers as the main targets of naval air power. Hence, in the early 1930s, the Imperial Japanese Navy adhered to no unified doctrine as to about how carriers would utilized in a fleet action and had no clear vision as to the role of air power in naval warfare. But with the continued increase in the range and power of aircraft, carriers became acknowledged for their ability to strike at targets beyond the range of surface guns and torpedoes. Within the IJN, including gunnery staffs as well as naval aviators, became convinced that carrier aircraft should be used for a preemptive strike against the enemy's carriers to achieve air superiority in the proximity of the surface battle. Around 1932–33, the IJN began to shift its aerial focus from targeting from the enemy's battleships to their aircraft carriers; and by mid-30s, with the improved performance of bombing aircraft particularly dive-bombers, the destruction of the enemy's carrier force became the primary focus of Japan's carrier forces. The emerging concept of a mass aerial attack also shifted the emphasis away from the protection of the main battle fleet to attacks on targets over the horizon. Essential to the implementation of such a tactic was the locating of the enemy before the enemy found the Japanese carriers. As a consequence, it was important to the Japanese that naval aircraft be able to "outrange the enemy" in the air, just as Japanese surface forces could do by naval gunnery and torpedo attacks. Subsequently, throughout the 1930s, the Japanese naval aviation emphasized range in its specifications for new aircraft.
caption: Mitsubishi B1M torpedo bomber.
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