The Imperial Japanese Navy Air Service or Kaigun Koku Hombu was a major force in the Pacific War during World War Two. The Japanese military acquired their first aircraft in 1910 and followed the development of air combat during World War One with great interest. They initially procured European aircrft 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, the Hosho, in 1922. Afterwards they embarked on a conversion program of several excess battlecruisers and battleships into aircraft carriers. The IJN Air service had the missiono of national air defence, deep strike, naval warfare etc. It retained this mission to the end.

The Japanese pilot training program was very selective and rigourious, producing a high-quality and long-serving pilot corps, called the Kokutai, who ruled the air in the Pacific during early World War Two. However, this program did not allow the Navy to rapidly replace lost pilots with quality and timely replacements. The resultant decrease in quality resulted in increasing casualties toward the end of the war. The Air Service was controlled by the Navy Staff of the Imperial Japanese Navy and the the Navy Ministry.

1st Air Fleet/Carrier Air Corps

The elite of the pilots were the carrier-based Air Corps (kokutai, later called koku sentai) whose size (from a handful to 80 or 90 aircraft) was dependent on both the mission and type of aircraft carrier that they were on. The large fleet carriers had three types of aircraft; fighters, level bombers/torpedo planes, and dive bombers. While the smaller carriers tended to have only two types of aircraft; fighters and dive bombers. The carrier-based kokutai numbered over 1500 pilots with over 1500 aircraft at the beginning of the Pacific War.

11th Air Fleet/Land Based Air Fleets

The IJN also maintained a shore-based system of air fleets called Koku Kantai and Area Air Fleets called homen kantai containing mostly twin engine bombers and seaplanes. The controlling unit was the 11th Air Fleet commanded by Vice Admiral Nihizo Tsukuhuru .

Strength

Each Air Fleet contained one or more Air Flotillas (commanded by Rear Admirals) each with two or more Air Groups. Each Air Group consisted of a base unit and 12 to 36 aircraft, plus 4 to 12 aircraft in reserve. Each Air Group consisted of several Air Divisions or hikotai of 9, 12 or 16 aircraft; this was the main IJN Air Service combat unit and was equivelent to the Imperial Japanese Army Air Service's Air Company. Each hikotai was commanded by a junior lieutenant or Warrant Officer or an experienced Chief Petty Officer, while most pilots were non commissioned officers. There were usually for sections in each division, each section or shotai had 3 or 4 aircraft and by mid 1944 it was common for a shotai to have 4 aircraft. There were over 90 Air Groups at the start of the Pacific War and each was assigned either a name or a number. The named Air Groups were usually linked to an particular navy air command or a navy base. They were usually numbered when they left Japan.

Air Group Identification

• Air Groups 200 to 399 - Fighter groups.
• Air Groups 400 to 499 - Float planes
• Air Groups 600 to 699 - mixed aircraft types.

Aircraft strength 1941

The IJN had over 3,089 aircraft in 1941 and 370 trainers.

• 1,830 first line aircraft including the following:
  • 660 fighters, mostly Mitsubishi Zero's
  • 330 Carrier based strike aircraft
  • 240 twin engined bombers
  • 520 seaplanes, and flying boats.

See Also

• List of military aircraft of Japan
• Imperial Japanese Navy Aviation Bureau