Many of the Imperial Japanese Army Air Force (JAAF) fighters were created by Nakajima Hikoki K.K., including the Ki-27, Ki-3 Hayabusa, and Ki-44 Shoki. Well into WWII, Nakajima concentrated their efforts on developing the new Army Type 4 Fighter Hayate. Its development began in Dec. 1941 in response to the JAAF demand for an all new general-purpose fighter, Ki-84. It was to exceed the speed and climbing ability of the Ki-44 Shoki; possess equal maneuverability and range to the Ki-43 Hayabusa , and display superb attack strength. The Nakajima Ha-45 engine was chosen, which was basically the 16-cylinder Sakae engine used on the Zero fighter and Ki-43 Hayabusa, with the following modifications: it was increased to 18-cylinders, made more lightweight, and had its power boosted to about 2000hp. Hayate was also equipped with 13mm armor plating and a 70mm armored windscreen, making it the first Japanese airplane equipped with pilot protection for the developmental stage. In August 1943, the Hayate made its first sortie over China. Hayate fighters were later sent to fight in the Philippines, Okinawa and so on. They were also used on the Japanese mainland to intercept and destroy incoming B29 bombers. Including two 12.7mm fuselage machine gun/two wing mounted 20mm cannon equipped bomber destroyer-interceptor, about 3500 Hayates were produced. In the final stages of WWII, the drop in both the quality of available materials and production process caused a decline in the rate of operation and performance of Hayate.
