the factory between March and June 1945. In contrast to the unreliable engines used by the Kawanishi N1K-J, Kawasaki Ki-61 and Nakajima Ki-84 that were keeping many of these aircraft grounded, the new engine was much more reliable. Although its maximum speed in level flight was a bit slow for 1945, the Ki-100 could dive with North American P-51 Mustangs and maintain speed after pullout, unlike most Japanese fighters. Two remaining problems continued to hamper Japanese fighters towards the end of the war, these being unreliable electrical systems and poor radio equipment, and while the latter was never resolved, the Ki-100's electrical system was less of a problem than with other types. The armament remained the same as was used on the Ki-61, which was two cowl-mounted calibre Ho-5 cannons, with 200 rounds per gun complemented by two wing-mounted Ho-103 machine guns with 250 rounds per gun. Fuselage improvements The Ki-100-I-Otsu were newly built as such, rather than being conversions, with a cut-down rear fuselage and improved canopy and 118 were produced from May through to the end of July 1945. This version also featured a modified oil cooler under the engine in a more streamlined fairing. High altitude improvements The Ki-100-II was fitted with a turbocharged water-methanol injected engine for improved high-altitude performance, mainly to improve interception capabilities against the Boeing B-29 Superfortresses, but only three prototypes were built, and none were used operationally. Due to a lack of space, no intercooler was installed, however performance was still enhanced above . Operational history The Ki-100 made its combat debut on the night of 9 March 1945 and suffered its first loss a month later on the night of 7 April 1945, when a single Ki-100 of the 18th Sentai was downed by a B-29 Superfortress after "attacking the formation again and again". Allied aircrews soon realised that they were facing a formidable new fighter. Although far fewer Ki-100s were available than Nakajima Ki-84s, it was an important fighter in the Army's inventory. A well-handled Ki-100 was able to outmanoeuvre any American fighter, including the P-51D Mustangs and Republic P-47N Thunderbolts which escorted the B-29s over Japan, and was comparable in speed, especially at medium altitudes. The Ki-100 was a tough opponent in the hands of an experienced pilot. The Ki-100 along with the Army's Nakajima Ki-84 and the Navy's Kawanishi N1K-J were equal to the latest Allied types in