Very soon after the design of the Ki-43 Hayabusa had been started by Nakajima, the company received instructions from the Imperial Japanese Army to initiate the design of a new interceptor fighter. In this case however, manoeuvrability was required to give precedence to overall speed and rate of climb, and the company's design team selected the 1,250 hp (932 kw) Nakajima Ha-141 as the powerplant for this new project. Of similar configuration to the Ki-43, the new Nakajima Ki-44 prototypes also incorporated the manoeuvring flaps that had been introduced on that aircraft, and carried an armament of two 7.7 mm (0.303 in) and two 12.7 mm (0.50 in) machine guns. First flown on August 1940, the Ki-44 was involved in a series of comparative trials against Kawasaki's Ki-60 prototype, based on the use of the Daimler-Benz DB 601 engine, and an imported Messerschmitt Bf 109E. The result of the evaluation and extensive service trials, showed the Ki-44 to be good enough to enter production, and it was ordered under the designation Army Type 2 Single seat Fighter Model 1A Shoki (demon), company designation Ki-44-Ia, which carried the same armament as the prototypes. A total of only 40 Ki-44-I aircraft was produced, including small numbers of the Ki-44-Ib armed with four 12.7 mm (0.50 in) machine guns, and the similar Ki-44-Ic with some minor refinements.

Nakajima Ki-44-IIb of the 23rd Sentai for home island defence in 1944 

When introduced into service the high landing speeds and limited manoeuvrability of the Shoki made it unpopular with pilots, and very soon the Ki-44-II with a more powerful Nakajima Ha-109 engine was put into production. Only small numbers of the Ki-44-IIa similarly armed to the Ki-44-Ia, were built, the variant being followed by the major production Ki-44-IIb which apart from the different engine was identical to the Ki-44-Ic. The Ki-44-IIc introduced much heavier armament, comprising of four 20 mm cannon or alternatively two 12.7 mm (0.50 in) machine guns and two 40 mm cannon, and these proved to be very effective when deployed against Allied heavy bombers attacking Japan. However the increased power had done nothing to eliminate the reasons for its unpopularity with the pilots, and in fact, the higher wing loading of this version meant that it had some violent reactions to high speed manoeuvres; however, it later regained their respect because of its capability as an interceptor.

Nakajima Ki-44-IIb of the Shinten (air superiority) unit of the 47th Sentai, Narimasu, Tokyo, summer 1944

Final production version was the Ki-44-III with a 2,000 hp (1491 kw) Nakajima Ha-145 radial engine, an increase in wing area and enlarged vertical tail surfaces, but comparatively few were built before production ended in late 1944. They included the Ki-44-IIIa and the similar Ki-44-IIIb, armed with four 20 mm cannon, and two 20 mm and two 37 mm cannon respectively.

Nakajima had built a total of 1,225 Ki-44's of all versions, including prototypes, and these were allocated the Allied codename 'Tojo'. They were deployed primarily in Japan, but were used also to protect vital targets, as in Sumatra where they defended the oil fields at Palembang. 

(Army Type 2 Single Seat Fighter Model 1A Shoki "Demon" - Nakajima Ki-44-IIb)

Allied Codename: Tojo

Type: Single Seat Fighter Interceptor

Powerplant: One 1,520 hp (1133 kw) Nakajima Ha-109 (Type 2) 14-cylinder radial piston engine.

Performance: Maximum speed 376 mph (605 km/h) at 17,060 ft (5200 m); cruising speed 249 mph (400 km/h); service ceiling 36,745 ft (11200 m).

Range: 1,056 miles (1700 km) with internal fuel stores.

Weight: Empty 4,641 lbs (2105 kg) with a maximum take-off weight of 6,598 lbs (2993 kg).

Dimensions: Span 31 ft 0 in (9.45 m); length 28 ft 10 in (8.79 m); height 10 ft 8 in (3.25 m); wing area 161.46 sq ft (15.00 sq m).

Armament: Two 12.7 mm (0.50 in) Type I (Ho-103) machine-guns in the upper decking fuselage and two 12.7 mm (0.50 in) Type I (Ho-103) machine-guns mounted in the wings.

Variants: Ki-44 (prototype SN 4401-4403), Ki-44-I(a) Army Type 2, Ki-44-Ib, Ki-44-Ic, Ki-44-IIa (Nakajima Ha-109 Army Type 2 radial engine rated at 1,450 hp), Ki-44-IIb, Ki-44-IIc, Ki-44-IIIa, Ki-44-IIIb (Two 20 mm Ho-5 cannons and two 37 mm Ho-203 cannon).

Operators: Japanese Army.