Unfortunately for the Japanese war effort, neither service cooperated with the other. Army and navy aircraft employed different electrical systems; when the Japanese developed an Identification, Friend or Foe (IFF) capability, army operators on Iwo Jima in 1944 could not identify Japanese navy aircraft as friendly. Further, aircraft factories were divided between those areas that made army planes and those producing naval aircraft, and each kept design developments secret from the other. There was no exchange of data. The navy's Zero fighter was superior to the army's Hayabusa, but the navy did not want to share the Zero with the army. If the army had adopted the Zero, the number of Japanese fighter aircraft produced during the war would have been greatly increased. There was little standardization between the Zero and Hayabusa, even in small screw parts.
Japan also failed to develop heavy bombers comparable to those of Britain and the United States. Not until January 1944 did the army and navy agree to develop a joint, 6-engine heavy bomber, dubbed the "Fugaku," but this project came too late and had to be abandoned. Finally, each service also concealed its weaknesses from the other; thus, it was 1945 before army leaders discovered how catastrophic the 1942 Battle of Midway had been for the Japanese naval air arm.
At the beginning of the Pacific war in December 1941, the Japanese army possessed 4,800 aircraft. Most army fighters were of the obsolescent Nakajima Ki-27 Type 97 ("Abdul" in the Allied recognition system). The army had only 50 first-class fighters—the Nakajima Ki-43 Hayabusa ("Oscar"), which made its debut over Malaya in December 1941. The Ki-43 gradually became the army's most numerous fighter; 5,751 were built during the war. Later, the army introduced new fighters: the Nakajima Ki-44 Shoki ("Tojo"), with initial deliveries in September 1942; the Kawasaki Ki-61 Hien ("Tony"), in August 1942; and the Nakajima Ki-84 Hayate ("Frank"), in April 1944. The best of Japan's wartime army fighters to reach mass production, the Ki-84 was superior to the North American P-51 Mustang and Republic P-47 Thunderbolt in certain respects. The Japanese army had no heavy bombers or dive-bombers and only three medium types: the Mitsubishi Ki-21 Type 97 ("Gwen"), the Nakajima Ki-49 Donryu ("Helen"), and the Mitsubishi Ki-67 Hiryu ("Peggy").
As of December 1941, the Imperial Japanese Navy air arm, which played a major role in the early battles in the Pacific, possessed 3,000 airplanes, 1,300 of which were with the fleet in 1941. Most numerous of its aircraft was the excellent, highly maneuverable Mitsubishi A6M Zero fighter ("Zeke"). Others included the Nakajima B5N Type 97 torpedo-bomber and light bomber ("Kate"); the Aichi D3A Type 99 carrier dive-bomber ("Val"); and two twin-engine, land-based medium bombers, the Mitsubishi G3M ("Nell") and the G4M Type 1 ("Betty"). Zero fighters took part in every major Japanese operation of the war. In the first six months of the war, the Zero was superior to any Allied fighter aircraft. Japan produced a total of 10,370 Zeros during World War II. As new Allied aircraft were introduced, the Japanese navy developed new aircraft, such as the Kawanishi NIK2-J Shiden ("George") and the Nakajima B6N Tenzan ("Jill").
In the Sino-Japanese War and the first stage of the Pacific war, the Japanese air forces met with considerable success. They dominated the skies over China and instituted strategic bombing of Chinese cities in 1938. The Japanese naval air arm was undoubtedly the best in the world, and Japanese pilots were among the best trained. In 1941, first-line Japanese pilots had 500 to 800 flying hours, and 50 percent of army pilots and 10 percent of navy pilots had combat experience against China and/or the Soviet Union.
On 7 December 1941, the naval air arm executed the attack on Pearl Harbor, conclusively demonstrating the supremacy of airpower in modern naval warfare and establishing the effective combination of carriers and aircraft. A few days later, navy land-based aircraft sank the British battleship Prince of Wales and the battle cruiser Repulse off Malaya. For the first time, a self-defending battleship under way had been sunk by aircraft, which showed that in the future, ships would require air protection. However, in 1942, Japanese air forces suffered heavy losses in the Battles of Midway and Guadalcanal. These battles spelled the ruin of the fine Japanese naval air arm and revealed the serious flaw of an inadequate pilot-replacement system; much of the trained naval air arm was lost in the battle and could not be replaced. The army also sustained heavy aircraft and pilot losses over New Guinea in 1943, and navy air squadrons were badly hurt at Truk and the Caroline Islands from February to April 1944.
The Battle of the Philippine Sea ("the great Marianas turkey shoot") in June 1944 and the Battle of Leyte Gulf in October 1944 finished off the Japanese naval air arm as an effective fighting force. The army and navy delivered new planes, such as the Hayate and Tenzan, but shortages of adequately trained pilots and fuel negated any advantage. By 1944, Japan was so short of aviation fuel that it could scarcely train its pilots; Japanese aviators had only about 120 hours of flying time before combat.
Japan produced some excellent, highly maneuverable aircraft during the war, but they tended to be lightly armored and caught fire easily. The Zero fighter was essentially unarmored, and Allied pilots dubbed the G4M Type 1 ("Betty") bomber "the flying cigarette lighter" because it so readily caught fire. Japanese aircraft simply could not sustain heavy damage. The planes also tended to be more lightly armed than their U.S. counterparts. When the Boeing B-29s began the strategic bombing of Japan, Japanese fighters had difficulty shooting them down. The Japanese planes also lacked airborne radar.
As Japan faced overwhelming Allied forces by late 1944, the military instituted kamikaze suicide attacks. Such strikes were ordered by Vice Admiral Onishi Takijiro during the Battle of Leyte Gulf, and they reached culmination in the Battle of Okinawa between April and June 1945. The kamikaze strike proved highly effective: the U.S. Navy sustained greater personnel losses from these attacks during the Battle of Okinawa than in all its previous wars combined. Yet even this new tactic could not turn the tide for Japan.
In the period between 1940 and 1945, the United States produced 297,199 aircraft; during the same period, Japan produced 74,656. In the Pacific war, the Japanese army lost 15,920 planes and the Japanese navy 27,190. Kotani Ken
Mainichi Series: Nihon Koukushi (History of Japanese aircraft). Tokyo: Mainichi Shinbunsya, 1979.; Marder, A. J. Old Friends, New Enemies. Oxford: Clarendon Press, 1981.; Roberts, J. B. Japanese Aircraft of the Pacific War. London: G. P. Putnam, 1979.