The A7M was to succeed the A6M Reisen. Design work started in 1940, but due to other production receiving the priority a prototype was not finished until 1944. Jiro Horikoshi designed the A7M.
On July 6, 1942, the Navy issued another set of specifications, 17-Shi, for a carrier fighter and be able to maneuver as well as the A6M3:
Jiro Horikoshi wanted the Mitsubishi MK9A (2,200 HP) engine to be used by the Navy wanted the Nakajima NK9K (2,000 HP) to be used.
The A7M had self sealing fuel tanks, armor for the pilot, and a bullet proof windshield.
In December 1944 an earthquake and air raids at the factory delayed production. Many of the prototypes were also destroyed.
The A7M1 prototype first flew on May 6, 1944, piloted by Eisaku Shibayama. Work was stopped on this prototype as it didn't meet the specifications. The Imperial Japanese Navy suspended trials for the A7M1 on July 30, 1944.
The sixth prototype had the Mitsubishi MK9A engine installed and it became the A7M2 prototype. On October 13, 1944, the A7M2 prototype flew and met the specifications.