By Justin Pyke

Editorial Note: In the final part of a three-part article, Justin Pyke examines American intelligence assessments of Japanese air power during the inter-war years. This final part examines issues between 1937 and the outbreak of war between America and Japan in 1941. Part one and two of this article can be found here and here.

Japan’s air services had successfully weaned themselves off of their foreign dependence by 1937. American intelligence assessments continued to identify the strategic and industrial weaknesses of Japanese air power accurately but became poor concerning technology and tactics. Japanese information security was tighter than it had ever been. Hence, American observers formed their conclusions through open sources and preconceived notions. When evidence emerged contradicting the prevailing view of Japan’s lack of technological innovation, they were ignored or explained away. Assessments of Japanese personnel began to swing toward a consistently negative view. These failures in assessing Japanese technology, tactics, and personnel from 1937-41 contributed to the defeats at the outset of the Pacific War.

 A captured Mitsubishi ARM ‘Zero’ in flight, c. 1944 (Source: National Naval Aviation Museum)

The Americans had relied on access to Japanese air stations and factories to gain their information until the early 1930s. This avenue was closed with the start of the war in China. In place of the old sources, American observers came to rely extensively on open sources, like official Japanese press releases, supplemented with the precious little information that could be drawn from chance sightings of Japanese aircraft by Westerners.[1] A meaningful assessment of Japanese air power’s performance in China, or detailed technical information of a specific aircraft, would surface on occasion. The information gained from open sources at best-reiterated views that had been in place for almost two decades and at worst became more critical and inaccurate about Japanese capabilities.

American assessments of the Japanese aviation industry remained accurate, despite Japan’s turn towards tight information security. However, the preconception that Japan could not innovate technologically remained pervasive. A July 1937 report was typical. It acknowledged the advances made by the Japanese aviation industry, accurately identified the numerous weaknesses present, and stated that a ‘dearth of local inventive ability’ was a critical failure.[2] Another report referred to the numerous industrial weaknesses as a ‘cancer,’ and went on to claim that Japan continued to rely on copies of foreign aircraft, acquired either through production licenses or ‘outright mimicry.’[3] American assessments combined recognition of the real weaknesses of Japan’s aviation industry with the fiction that it still relied on the copying of foreign aircraft designs.

The American emphasis on Japanese industrial weakness was warranted. The continued shortage of machine tools, skilled labour, heavy equipment, and modern industrial techniques contributed to Japan’s lack of an aircraft reserve, slower rates of production, poor quality and quantity of spare parts, and the numerous other issues that undermined Japanese air power.[4] Greg Kennedy has emphasised this point when he stated that to view:

[tactical] success as demonstrative of the overall ability of Japan to manifest effective, modern air power is to misunderstand fundamentally the core attributes of air power.[5]

Ultimately, the weaknesses of Japanese industry identified by the Americans before the war worked to cripple the offensive capabilities of the Imperial Japanese Army Air Service (IJAAS) and Imperial Japanese Naval Air Service (IJNAS) during it.

 A Kawasaki Ki-61 ‘Tony’ of the 149th Shimbu Unit at Ashiya airfield in Fukuoka, Japan, c. 1945 (Source: Wikimedia)

The most egregious error in American reporting from mid-1937 onward concerned the preconception that Japan was incapable of designing its own aircraft. Exceptions to this trend did exist, but they were easily drowned out by the overwhelming number of reports that reiterated the same trope of Japanese unoriginality.[6] Fictional aircraft were given corresponding European designs that the Japanese supposedly had copied.[7] When the Americans received hard evidence of Japanese technological innovation, these indicators were ignored or misunderstood. Excellent American intelligence on the B5N Carrier Attack Bomber (‘Kate’) was not used as evidence that Japan had moved away from copying foreign designs.[8] The G3M was immediately assumed to be a copy of the German Junkers Ju-86, while another report stressed the bomber was a Heinkel design with Junkers’ ailerons. In fact, the superlative bomber was indigenous in origin.[9] Even when American observers disagreed on what the aircraft was a copy of, there was no doubt that it had to be a copy of something.

These preconceptions were all the more dangerous as Japan introduced new aircraft that it would use against the West in 1941. The most famous of these was the A6M Carrier Fighter (‘Zero’/‘Zeke’). Despite some accurate reporting on the aircraft, it remained largely unknown in Western aviation circles.[10] In one instance, the testimony of a captured Japanese bomber pilot caused confusion when he explained that the A6M was designed to dive on the enemy, then zoom upwards and prepare for another dive, but not to engage in extensive combat aerobatics. This reflected IJNAS fighter doctrine, which was similar to that of the Americans, rather than the true capabilities of the A6M. The Americans interpreted the testimony to mean the new fighter lacked manoeuvrability.[11] The underestimation of the A6M seems like a minor error when viewed in isolation. Indeed, American pilots quickly gained an understanding of the fighter from their first combat encounters.[12] However, it was only a symptom of a much broader issue. Evidence that the Japanese had achieved rough technological parity with the United States was belittled or ignored. Individual Japanese aircraft may have been better or worse than foreign counterparts for their intended roles, but American assessments assumed a clear and decisive technological advantage where none existed. Nor did Japanese technological innovation stop with the attack on Pearl Harbor. Both air services introduced aircraft, such as the Nakajima Ki-84 Fighter (Hayate/‘Frank’), that matched some of the best American designs throughout the war.[13] The problem was not that leading-edge Japanese aircraft designs were worse than their American counterparts, but that they never were able to replace their ageing predecessors in sufficient numbers to matter.

The Americans dismissed not just Japanese innovation, but its personnel and tactics. American views of Japanese personnel became increasingly negative after the start of the war in China. Assessments of Japanese factory workers and mechanics significantly reduced in frequency and classified reporting on aircrews indicated that they were of poor to mediocre quality.[14] American observers also continued to emphasize Japan’s lack of pilot reserves and training facilities.[15] Popular literature took a firm stand on Japanese personnel and often relied heavily on racism and national characteristics. One such work listed a number of Japanese racial defects, and summarised them as ‘daring but incompetent aviators.’[16] Classified sources never degraded into this kind of drivel, despite American intelligence shortcomings concerning Japanese tactics and technology.

 A captured Imperial Japanese Navy Aichi B7A2 ‘Grace’, c. 1945. This was one of many capable indigenous aircraft introduced by the Japanese air services during the Pacific War. (Source: Wikimedia)

Surprisingly little reporting discussed Japanese aerial performance in China, and reports that did provide a more balanced, and accurate, assessment of Japanese capabilities.[17] Occasionally, Chinese pilots were interviewed on their combat experience against the Japanese. One report from September 1940 concluded that dive bombing by the IJAAS and IJNAS was ‘very poor,’ while horizontal bombing had ‘improved tremendously.’ Discipline among IJNAS twin-engine bombers was rated ‘excellent,’ and the carrier air groups were given particularly high praise. The most important piece of information provided by Chinese pilots was that the Japanese sent fighter escorts with their bombers whenever possible.[18] However, given the mixed quality of the Republic of China Air Force, their views concerning Japanese capabilities were easily dismissed.[19]

The American underestimation of the Japanese air services’ personnel, tactics, and technology from 1937-41 contributed to, though by no means caused, the early defeats in the Pacific War. However, Japan’s inability to rectify the fundamental problems within its air services and aviation industry crippled its air power as the war progressed, just as American observers had predicted. The accurate assessment that Japan could not win a prolonged war of attrition in the air against the United States was what mattered most. However, the errors in assessing Japanese tactics and technology caused serious problems over the short term. In their haste to predict the setting of the Sun, the Americans failed to appreciate the danger of its rise.

Header Image: A Mitsubishi A6M2 ‘Zero’/‘Zeke’ at the US National Advisory Committee for Aeronautics Langley Research Center, Virginia on 8 March 1943. On 4 June 1942, a Japanese task force launched a strike against Dutch Harbor, Alaska from the aircraft carriers Ryujo and Junyo. Petty Officer Tadayoshi Koga was flying an A6M2 from the Ryujo. On the way back to his carrier, he discovered of bullets had pierced his fuel tanks and he headed for an emergency landing on Akutan Island. However, the plane flipped over on its back during the landing, and Koga was killed. The A6M itself was only slightly damaged. A Japanese submarine failed to locate Koga or his plane, but five weeks later an American naval scouting party found the Japanese fighter. The A6M2 was salvaged and shipped back to the USA where it was repaired, and went through an exhaustive series of tests in order to gain information about its strengths and weaknesses. (Source: Wikimedia)

[1] A-1-m 15776, Dive Bombing in the Japanese Aviation, July 27, 1938, Naval Attaché Reports, 1886-1939, Box 68, RG 38, NA; Japanese Naval Activities in China, July 29, 1940, Naval Attaché Records, 1939-1941, 1940 File 59-124, RG 38, NA; Comments on Naval Aviation by Japanese Naval Aviators, August 23, 1941, Naval Attaché Records, 1939-1941, 1941 File 62, RG 38, NA.

[2] Expansion of Aircraft Manufacturing Industry, July 21, 1937, Selected Naval Attaché Reports Relating to the World Crisis, 1937-1943, Roll 2, RG 38, NA, p. 1.

[3] The Aircraft Industry in Japan, August 5, 1939, Naval Attaché Records, 1939-1941, 1939 File 165-233, RG 38, NA, pp. 1-2.

[4] Mark R. Peattie, Sunburst: The Rise of Japanese Naval Air Power, 1909-1941 (Annapolis: Naval Institute Press, 2001), p. 100; Erich Pauer, ‘Japan’s technical mobilization in the Second World War,’ in Erich Pauer (ed.), Japan’s War Economy (New York, NY: Routledge, 1999), pp. 54-5; Hagiwara Mitsuru, ‘The Japanese Air Campaigns in China, 1937-1945,’ in Mark Peattie, Edward Drea, and Hans Van de Ven (eds.), The Battle for China: Essays on the Military History of the Sino-Japanese War of 1937-1945 (Stanford, CA: Stanford University Press, 2011), p. 243; Jonathan B. Parshall and Anthony P. Tully, Shattered Sword: The Untold Story of the Battle of Midway (Washington D.C.: Potomac Books, 2005), p. 89; Eric M. Bergerud, Fire in the Sky: The Air War in the South Pacific (New York: Basic Books, 2009), p. 21, 46; Sakai Saburo, Martin Caidin, and Fred Saito, Samurai! (Annapolis: Naval Institute Press, 1991), p. 242.

[5] Greg Kennedy, ‘Anglo-American Strategic Relations and Intelligence Assessments of Japanese Air Power, 1934-1941,’ The Journal of Military History, 74:3 (2010), p. 772.

[6] William M. Leary, ‘Assessing the Japanese Threat: Air Intelligence Prior to Pearl Harbor,’ Aerospace Historian, 34:4 (1987), p. 274; 2085-947, The Capabilities of Japan in Military Aviation, June 23, 1939, US Military Intelligence Reports, Japan, 1918-1941, Reel 31, University Press of America, p. 1.

[7] Airplane Characteristics – Mitsubishi Type Zero Fighter, November 9, 1940, Naval Attaché Records, 1939-1941, 1940 File 125-202, RG 38, NA; New Dive Bomber in Production, August 2, 1940, Naval Attaché Records, 1939-1941, 1940 File 59-124, RG 38, NA.

[8] New Types of Aircraft, July 17, 1939, Naval Attaché Records, 1939-1941, 1939 File 89-164, RG 38, NA; Type 97 Torpedo-Bomber, November 16, 1939, Naval Attaché Records, 1939-1941, 1939 File 234-281, RG 38, NA; Specifications of Japanese Naval Bomber, Model 97, June 4, 1940, Naval Attaché Records, 1939-1941, 1940 File 59-124, RG 38, NA.

[9] Richard M. Bueschel, Mitsubishi/Nakajima G3M1/2/3 96 Rikko L3Y1/2 In Japanese Naval Air Service (Atglen: Schiffer Publishing, 1997), p. 20; Description of Navy Heavy Bomber, Type 96, July 26, 1939, Naval Attaché Records, 1939-1941, 1939 File 165-233, RG 38, NA; René J. Francillon, Japanese Aircraft of the Pacific War, Second Edition (London: Putnam Aeronautical Books, 1979), p. 350.

[10] Thomas G. Mahnken, Uncovering Ways of War: U.S. Intelligence and Foreign Military Innovation, 1918-1941 (Ithaca: Cornell University Press, 2002), pp. 79-80; Horikoshi Jiro, Eagles of Mitsubishi: The Story of the Zero Fighter, trans. Shojiro Shindo and Harold N. Wantiez (Seattle: University of Washington Press, 1981), p. 107.

[11] Leary, ‘Assessing the Japanese Threat,’ pp. 275-76; Horikoshi, Eagles of Mitsubishi, p. 85; John B. Lundstrom, The First Team: Pacific Naval Air Combat from Pearl Harbor to Midway (Annapolis: Naval Institute Press, 2005), p. 486; Roger Letourneau and Dennis Letourneau, Operation KE: The Cactus Air Force and the Japanese Withdrawal from Guadalcanal (Annapolis: Naval Institute Press, 2012), p. 13; Sakai, Samurai, p. 83.

[12] John B. Lundstrom, The First Team and the Guadalcanal Campaign: Naval Fighter Combat from August to November 1942 (Annapolis: Naval Institute Press, 2005), pp. 535-36.

[13] See: Francillon, Japanese Aircraft of the Pacific War; Richard M. Bueschel, Nakajima Ki.84a/b Hayate in Japanese Army Air Force Service (Canterbury: Osprey Publishing, 1971).

[14] Notes on Japanese Naval Aviation, August 4, 1939, Naval Attaché Records, 1939-1941, 1939 File 165-233, RG 38, NA; Dropping of Aircraft Torpedoes by Japanese Naval Aircraft, September 26, 1939, Naval Attaché Records, 1939-1941, 1939 File 165-233, RG 38, NA; A-1-m 15776, Aerial Operations, August 2, 1940, Naval Attaché Reports, 1886-1939, Box 68, RG 38, NA; 2085-956, Handbook on the Air Services of Japan, September 27, 1940, US Military Intelligence Reports, Japan, 1918-1941, Reel 31, University Press of America, p. 36, 79.

[15] 2085-908, Military Aviation – General, July 29, 1937, US Military Intelligence Reports, Japan, 1918-1941, Reel 30, University Press of America, p. 3; W.D. Puleston, The Armed Forces of the Pacific: A Comparison of the Military and Naval Power of the United States and Japan (New Haven: Yale University Press, 1941), p. 231.

[16] Fletcher Pratt, Sea Power and Today’s War (New York: Harrison-Hilton Books, 1939), pp. 177-78.

[17] 2085-947, The Capabilities of Japan in Military Aviation, pp. 1-3.

[18] Comment on Japanese Air Force by Chinese Aviators, September 17, 1940, Naval Attaché Records, 1939-1941, 1940 File 125-202, RG 38, NA; Peattie, Sunburst, p. 110, 123.

[19] Peter Harmsen, Shanghai 1937: Stalingrad on the Yangtze (Havertown: Casemate Publishers, 2013), p. 30.

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