and in July 1942, it instructed Mitsubishi to produce a further improved version, the Ki-46-III. This had more powerful, fuel-injected Mitsubishi Ha-112 engines, and a redesigned nose, with a fuel tank ahead of the pilot and a new canopy, smoothly faired from the extreme nose of the aircraft, eliminating the "step" of the earlier versions. The single defensive machine gun of the earlier aircraft was also omitted. The new version first flew in December 1942, demonstrating significantly higher speed (630 km/h (391 mph) at 6,000 m (19,700 ft)). The performance of the Ki-46-III even proved superior to that of the aircraft intended to replace it (the Tachikawa Ki-70), which as a result did not enter production. In an attempt to yet further improve the altitude performance of the Ki-46, two prototypes were fitted with exhaust driven turbosupercharged Ha-112-II-Ru engines. This version first flew in February 1944, but only two prototypes were built. Mitsubishi factories made a total of 1,742 examples of all versions (34 units Ki-46-I, 1093 units Ki-46-II, 613 units Ki-46-III, 4 units Ki-46-IV）during 1941–44. Operational history This aircraft was first used by the Japanese Army in Manchukuo and China, where seven units were equipped with it, and also at times by the Japanese Imperial Navy in certain reconnaissance missions over the northern coasts of Australia and New Guinea. The Japanese Army used this aircraft for the same type of missions (which were not authorized) over present-day Malaysia during the months before the Pacific War. Later, it was used for high altitude reconnaissance over Burma, Indochina, Thailand, and the Indian Ocean. The Ki-46 was regarded by the British RAF in Burma as a difficult aircraft to counter, only occasionally intercepting them successfully. On September 25, 1944, Flying Officer Wittridge shot down a Ki-46, using a personally modified Spitfire Mk VIII. Wittridge had removed two machine guns and the seat armour, and also polished the wing leading edges to gain extra speed. The leading American fighter pilot Richard Bong, flying a P-38 Lightning, managed to shoot down a Ki-46 over the coast of Papua New Guinea in late 1942. In 1944–45, during the last days of the war, it was modified as a high-altitude interceptor, with two 20 mm cannons in the nose and one 37 mm (1.46 in) cannon in an "upwards-and-forwards" position – almost like the Luftwaffes Schräge Musik night fighter cannon emplacements – for fighting USAAF B-29