The Nakajima Ki-43 Hayabusa was born from a 1937 Japanese Army requirement to replace the Ki-27 fighter with an aircraft that retained its agility but offered greater speed, range, and climb. Designer Hideo Itokawa first flew the prototype in January 1939, but it disappointed test pilots, being slower and less maneuverable than its predecessor. Through 1939 and 1940, Nakajima refined the design, cutting weight, lengthening the fuselage, and adding Fowler-type “butterfly” flaps that dramatically improved turning ability. By the thirteenth prototype, the aircraft met expectations, and production began in late 1939. The first production version, the Ki-43-I, entered service in 1941. Light and nimble, it could outmaneuver nearly any opponent. Its Ha-25 engine and light frame gave it excellent climb and agility, though top speed was only about 308 mph. Armament was modest, usually just two cowling-mounted machine guns, and it lacked armor or self-sealing fuel tanks, making it vulnerable to even light enemy fire. Despite this, its agility made it a formidable opponent in early battles across China, Southeast Asia, and the Pacific. American pilots often mistook it for the Navy’s A6M Zero, earning it the nickname “Army Zero.” In 1942, the improved Ki-43-II appeared with a more powerful Ha-115 engine, a three-bladed propeller, stronger wings, and the addition of pilot armor and crude self-sealing fuel tanks. These features slightly reduced agility but improved survivability. It could also carry drop tanks or bombs, extending its versatility. Production expanded beyond Nakajima to Tachikawa, though shortages limited output at some facilities. By 1944, development shifted to the more advanced Ki-84, but Tachikawa continued building the Ki-43 into the war’s final months. The last major version, the Ki-43-III, used the Ha-115-II engine, boosting top speed to 358 mph. By then, however, Allied aircraft like the P-51 Mustang and P-47 Thunderbolt had far outclassed it in speed, firepower, and protection. The Hayabusa remained highly maneuverable, but its light structure and limited armament left it increasingly vulnerable. Many late-war Ki-43s were used in kamikaze missions as Japan faced defeat. By war’s end, 5,919 Ki-43s had been built, making it the second most produced Japanese fighter after the Zero. Though fragile and lightly armed, the Hayabusa gained a reputation for agility and was central to Japan’s early successes. It served across China, Southeast Asia, and the Pacific, remaining in frontline use until 1945, and is remembered as one of the iconic Japanese fighters of the war.