Japanese Navy Organization

Early War Organization (from smallest to largest)

Carrier Divisions - Koku Sentais - These were the smallest groups of the Japanese Navy. The Koku Sentais consisted of two aircraft carriers and a varying number of Koku Sentais.

Area Fleets - Homen Kantais

Air Fleets - Koku Kantais

Fleets - Kantais

Navy Air Headquarters - Kaigun Koku Hombu - Responsible for aircraft, engines and equipment of the Navy, as well as testing of said equipment. They were also in charge of training of flight and maintenance personnel.

Chief of Navy General Staff - Gunreibu Socho

Imperial General Headquarters - Daihonei

Late War Reorganization

Reorganization was caused late in the war by the necessity of adding land based planes to their arsenal, mainly because they had so few carriers left.

Naval Air Corps - Kokutais

Koku Kanais consisted of

• One or more Air Flotillas called Koku Sentais
  • Further subdivided into Naval Air Corps or Kokutais. These had a strength of up to 150 aircraft or one or more types.
  • Also they were often broken into even smaller groups called Area Fleets or Homen Kantais

References:

1) Japanese Aircraft of the Pacific War by Rene' J. Francillon. Putnam Aeronautical Books, 1970