Until the Royal Air Force captured a Nakajima Ki-43 Hayabusa virtually intact in the spring of 1942, Allied pilots knew little about the planes they were meeting in the air, and even less about the Japanese Army Air Force units opposing them. The situation has improved very little over the years. JAAF records of the air war in the Pacific are necessarily sketchy, since some units -- including the 77th fighter sentai that bore the brunt of combat against the AVG -- were destroyed during the terrible retreats of 1944 and 1945.
The basic Japanese air combat unit was the sentai, equivalent to a USAAF group, though with only half the aircraft. With an effective strength of between 30 and 40 aircraft, the sentai was commanded by a major or lieutenant colonel who was himself a flying officer. Moving up the chain of command, two or more sentais -- often a fighter group, a heavy-bomber group, and a light-bomber or ground-support group -- made up a hikodan, equivalent to a USAAF wing and usually commanded by a colonel. Two or more hikodans made up a hikoshidan, equivalent to a geographical air force and commanded by a general officer.