Mitsubishi J2M Raiden 'Thunderbolt'... ( Allied reporting name ' JACK ' ) The J2M was designed by Jiro Horikoshi, creator of the A6M Zero, to meet the 14-Shi (14th year of the Showa reign, or 1939) official specification. It was to be a strictly local-defense interceptor, intended to counter the threat of high-altitude bomber raids, and thus relied on speed, climb performance, and armament at the expense of manoeuvrability. The J2M was a sleek, but stubby craft with its over-sized Mitsubishi Kasei engine buried behind a long cowling, cooled by an intake fan and connected to the propeller with an extension shaft. Pilot visibility was poor, but a domed canopy introduced later in production partially alleviated this concern. Teething development problems stemming from the Kasei engine, unreliable propeller pitch change mechanism and the main undercarriage members led to a slowdown in production. A continual set of modifications resulted in new variants being introduced with the ultimate high-altitude variant, the J2M4 Model 34 flying for the first time in August 1944. It had a 1,420 hp Kasei 23c engine equipped with a turbo supercharger (mounted in the side of the fuselage just behind the engine) that allowed the rated power to be maintained up to 9,100 m (29,900 ft) Two upward-aimed, oblique-firing (aimed at seventy degrees) 20 mm cannons, mounted in the German Schräge Musik style, were fitted behind the cockpit with the four wing cannons retained. Unresolved difficulties with the turbo supercharger caused the project to be terminated after only two experimental J2M4s were built. The first few produced J2M2s were delivered to the development units in December 1942 but severe problems were encountered with the engines. Trials and improvements took almost a year and the first batch of the serial built J2M2 Model 11 was delivered to 381st Kokutai in December 1943. Parallel with the J2M2, production of the J2M3 Raiden Model 21 started. The first J2M3s appeared in October 1943 but deliveries to combat units started at the beginning of February 1944. The Raiden made its combat debut in June 1944 during the Battle of the Philippine Sea. Several J2Ms operated from Guam and Saipan and a small number of aircraft were deployed to the Philippines. Later, some J2Ms were based in Chosen airfields, Genzan (Wonsan), Ranan (Nanam), Funei (Nuren), Rashin (Najin) and Konan under Genzan Ku, for defending these areas and fighting against Soviet Naval Aviation units. Primarily designed to defend against the Boeing B-29 Superfortress, the lack of a turbocharger handicapped the aircraft at high altitude. 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. Two captured J2Ms were U.S. Technical Air Intelligence Command (TAIC) tested using 92 octane fuel plus methanol, with the J2M2 (Jack11) achieving a speed of 655 km/h (407 mph) at 5,520 m (17,400 ft), and J2M3 (Jack21) achieving a speed of 671 km/h (417 mph) at 4,980 m (16,600 ft).