Curiously, the Japanese Army Air Force (JAAF) was slower than the navy in adopting more innovative and potent fighter designs. One reason was its longer adherence to the Japanese penchant for comparing aerial combat to the swordsman’s art of kendo, stressing dexterity of maneuver. Finally, in June 1935, the Koku Hombu (Army Headquarters) issued a requirement for an “advanced fighter” to replace the Kawasaki Ki.10 biplane. The new fighter was to be capable of 280 miles per hour in level flight and of reaching 16,405 feet (5,000 meters) in less than six minutes, but would still mount two 7.7mm Type 89 machine guns.
Nakajima’s design team, led by Tei Koyama and assisted by Minoru Ota and Hideo Itokawa, had already had some experience with externally braced monoplane designs when they learned of the new army requirement. They went on to design a small cantilever monoplane around the Nakajima Kotobuki II-Kai nine-cylinder radial—a license-built version of the Bristol Jupiter—using all-metal stressed-skin construction. As with the A5M, fixed landing gear enclosed within two streamlined fairings was selected over the heavier and more complex retractable undercarriage, but an enclosed canopy was incorporated into the second prototype. Increased wing area and the incorporation of wing flaps kept the fighter maneuverable enough to satisfy the Koku Hombu, which chose it over its faster competitor, the Kawasaki Ki.28, following trials in the spring of 1937. Powered by an improved 710-horsepower Nakajima Ha-I-Otsu engine driving a two-bladed all-metal two-pitch (ground-adjustable) Sumitomo PE propeller, the production version of the Nakajima Ki.27-Otsu Type 97 fighter had a maximum speed of 291 miles per hour at 13,125 feet.
So confident was Nakajima in its new fighter that it was making production preparations at its new plant at Ota even before the army’s order became official on December 27, 1937. Even the most conservative pilots were delighted with the new fighter’s maneuverability, as well as with its higher performance.
Eager to blood the new fighter in combat, the army dispatched three of the first planes to leave the assembly line to the 1st Chutai of the 2nd Hiko Daitai (Air Battalion), which was then flying Ki.10s from Yangzhou, northern China. Just one week after their arrival, on April 10, 1938, Capt. Tateo Kato, commander of the 1st Chutai, was leading the trio along with twelve Ki.10s on patrol near Ma Muchi when they encountered eighteen Polikarpov I-152s (also called I-15bis, which were upgraded I-15s with cabane struts in place of the gulled upper wings) returning from an attack on Japanese headquarters at Chao Chuang. The Japanese promptly attacked the lower formation of eleven I-152s of the 4th Pursuit Group at 4,500 meters altitude, and in the dogfight that followed, Kato’s Ki.27s zeroed in on Lt. Chang Guangming, who tried to escape with a climbing half-roll before he was hit. Bailing out just before his plane caught fire, Chang survived a Japanese attempt to strafe him in his parachute before alighting with an injured back.
At that point the seven I-152s of the 3rd Pursuit Group’s 8th Squadron, which were five hundred meters above the 4th Group’s flight, dived on the Japanese. The 8th’s deputy commander, Capt. Zhu Jiaxun, shot Sgt. Maj. Risaburo Saito off the tail of a 23rd Pursuit Squadron I-152, only to see the Ki.27 veer away to collide with Lt. Chen Huimin’s Polikarpov. Chen managed to bail out before both planes crashed, surviving with a leg injury. Meanwhile, the two remaining Ki.27s shot the cowling off Zhu’s plane, but he managed to evade them and force landed in a wheat field. Zhu’s and a second force-landed plane were subsequently recovered for repair. He was credited with Saito as the second of three victories he would score in I-152s; he would later add two more in Gloster Gladiators.
By the time the two sides finally disengaged, the Japanese had claimed twenty-four Chinese planes—more than they had been fighting—including two for Kato, two for Warrant Officer Morita, and a posthumous credit for Saito. Among the Ki.10 pilots, Sgt. Tokuya Sudo was credited with two and 1st Lt. Iori Sakai with three, but Lt. Yonesuke Fukuyama returned to base with wounds from which he died in hospital shortly after. Two Ki.10s force landed short of Yangzhou, and two others crash-landed on the airfield. Actual Chinese losses were two 4th Pursuit Group planes shot down, with Sun Jinjen killed, and three others, flown by Lin Yuexing, Wang Denbi, and Li Tingcai, force landing due to fuel exhaustion, but which were later recovered; a 3rd Pursuit Group plane lost with its pilot, Liang Zihang; and two 3rd Pursuit planes returning with their pilots, Liu Tianlung and Huang Yin, wounded.
Over the next few weeks, the 2nd Daitai supported the army’s Hsuchow campaign, intended to give the Japanese complete control of the Peking-Nanking railway. Chinese aerial opposition became infrequent, but on May 20, three Ki.27s of the Daitai’s headquarters flight took on ten Chinese, resulting in three credited to Capt. Mitsugu Sawada, one to Lt. Katsumi Anma, and one to Sgt. H. Wada, as well as seven more by the Ki.10s. In actuality, four I-152s of the 17th Pursuit Squadron were shot down, Zhu Qunqui and Qiu Guo bailing out of their flaming planes. In addition, Zhang Sheungren and William Tang force landed their shot-up fighters, and that of their commander, Sen Jiuliu, returned damaged, while two of the 22nd Pursuit Group’s Hawk IIIs, 2201 flown by Feng Yuhe and Chao Mosheng’s 2205, never returned.
The 2nd Hiko Daitai was still in the process of replacing its Ki.10s with Ki.27s in August 1938 when a restructuring of the JAAF resulted in its being redesignated the 64th Koku Sentai (Air Regiment). Adoption of the Ki.27 proceeded rapidly thereafter, and the fighter went on to its most celebrated period during the undeclared conflict between Japan and the Soviet Union in the Nomonhan region of Mongolia and Manchuria in the summer of 1939.