Soviet Naval Aviation units. Primarily designed to defend against the Boeing B-29 Superfortress, the type was handicapped at high altitude by the lack of a turbocharger. However, its four-cannon armament supplied effective firepower and the use of dive and zoom tactics allowed it to score occasionally. Insufficient numbers and the American switch to night bombing in March 1945 limited its effectiveness. J2Ms took part in one of the final aerial combats of the Second World War when four Raidens, accompanied by eight Mitsubishi A6M Zeros, all belonging to the 302nd Kokutai, intercepted a formation of US Navy F6F Hellcats from the aircraft-carrier USS Yorktown (CV-10) during the morning of 15 August 1945 over the Kanto Plain. In the engagement, that took place only two hours before Japan officially announced its surrender, four Hellcats were lost along with two Raidens and two Zeros. U.S. Technical Air Intelligence Command (TAIC) tested two captured J2Ms using 92 octane fuel plus methanol and calculated maximum speeds using measurements. The J2M2 (Jack11) achieved a speed of 655 km/h (407 mph) at 5,520 m (17,400 ft), and the J2M3 (Jack21) achieved a speed of 671 km/h (417 mph) at 4,980 m (16,600 ft). Variants J2M1 Prototype: fitted with the 1,044 kW (1,400 hp) Mitsubishi MK4C Kasei 13 14-cylinder air-cooled radial engine, and armed with two 7.7 mm (.303 in) Type 97 machine guns in the upper fuselage and two wing-mounted 20 mm Type 99 Model II cannon. - Eight builds. J2M2 Model 11: Powered by 1,379 kW (1,850 hp) Mitsubishi MK4R-A Kasei 23a 14-cylinder radial engine, same armament as the J2M1. J2M3 Model 21: Armed with two wing-mounted 20 mm Type 99 Model II cannon and two wing-mounted 20 mm Type 99 Model I cannon. J2M3a Model 21A: Armed with four wing-mounted 20 mm Type 99 Model II cannon. J2M4 Model 32: Prototype fitted with the 1,357 kW (1,820 hp) Mitsubishi MK4R-C Kasei 23c engine. Many armament configurations have been reported, e.g., fuselage-mounted oblique-firing 20 mm Type 99 Model I cannon designed to fire upward as it passed underneath a bomber, two wing-mounted 20 mm Type 99 Model II cannon, and two wing-mounted 20 mm Type 99 Model I cannon. J2M5 Model 33: High altitude variant powered by 1,357 kW (1,820 hp) Mitsubishi MK4U-A Kasei 26a engine with mechanically driven supercharger, giving increased high-altitude speed at the expense of range. Two 20 mm Type 99 cannon