In 1934, the Imperial Japanese Navy prepared a specification for an advanced fighter, requiring a maximum speed of 350 km/h (220 mph) at 3,000 m (9,800 ft) and able to climb to 5,000 m (16,000 ft) in 6.5 minutes.
This 9-shi (1934) specification produced designs from both Mitsubishi and Nakajima.

Mitsubishi assigned the task of designing the new fighter to a team led by Jiro Horikoshi (original creator of the similar but unsuccessful Mitsubishi 1MF10, and later responsible for the famous A6M Zero).
The resulting design, designated Ka-14 by Mitsubishi, was an all-metal low-wing fighter, with a thin elliptical inverted gull wing and a fixed undercarriage, which was chosen as the increase in performance (estimated as 10% in drag, but only a mere 3% increase in maximum speed) arising from use of a retractable undercarriage was not felt to justify the extra weight.
The first prototype, powered by a 447 kW (600 hp) Nakajima Kotobuki 5 radial engine, flew on 4 February 1935.
The aircraft far exceeded the requirements of the specification, with a maximum speed of 450 km/h (280 mph) being reached.
The second prototype was fitted with a revised, ungulled wing, and after various changes to maximize maneuverability and reduce drag, was ordered into production as the A5M.
With the Ka-14 demonstrating excellent performance, the Imperial Japanese Army Air Force ordered a single modified prototype for evaluation as the Ki-18.
While this demonstrated similar performance to the Navy aircraft and hence was far faster than the IJAAF's current fighter, the Kawasaki Ki-10 biplane, the type was rejected by the army owing to its reduced maneuverability.
The Army then produced a specification for an improved advanced fighter to replace the Ki-10.
Mitsubishi, busy turning the Ka-14 into the A5M, submitted a minimally changed aircraft as the Ki-33, this being defeated by Nakajima's competing aircraft, which was ordered into service as the Ki-27.
In 1934, the Imperial Japanese Navy prepared a specification for an advanced fighter, requiring a maximum speed of 350 km/h (220 mph) at 3,000 m (9,800 ft) and able to climb to 5,000 m (16,000 ft) in 6.5 minutes. This 9-shi (1934) specification produced designs from both Mitsubishi and Nakajima.
Mitsubishi assigned the task of designing the new fighter to a team led by Jiro Horikoshi (original creator of the similar but unsuccessful Mitsubishi 1MF10, and later responsible for the famous A6M Zero). The resulting design, designated Ka-14 by Mitsubishi, was an all-metal low-wing fighter, with a thin elliptical inverted gull wing and a fixed undercarriage, which was chosen as the increase in performance (estimated as 10% in drag, but only a mere 3% increase in maximum speed) arising from use of a retractable undercarriage was not felt to justify the extra weight. The first prototype, powered by a 447 kW (600 hp) Nakajima Kotobuki 5 radial engine, flew on 4 February 1935. The aircraft far exceeded the requirements of the specification, with a maximum speed of 450 km/h (280 mph) being reached. The second prototype was fitted with a revised, ungulled wing, and after various changes to maximize maneuverability and reduce drag, was ordered into production as the A5M.
With the Ka-14 demonstrating excellent performance, the Imperial Japanese Army Air Force ordered a single modified prototype for evaluation as the Ki-18. While this demonstrated similar performance to the Navy aircraft and hence was far faster than the IJAAF's current fighter, the Kawasaki Ki-10 biplane, the type was rejected by the army owing to its reduced maneuverability. The Army then produced a specification for an improved advanced fighter to replace the Ki-10. Mitsubishi, busy turning the Ka-14 into the A5M, submitted a minimally changed aircraft as the Ki-33, this being defeated by Nakajima's competing aircraft, which was ordered into service as the Ki-27.
Mitsubishi A5M