As my thesis nears completion, I have decided to write a relatively short summary of my findings here since I'm sure it will interest at least some of you fine people. As the title of the thread suggests, I have done a lot of research and writing regarding American intelligence assessments of Japanese air and naval power during the interwar period. To begin, net assessment is done through looking at both how strong the intelligence target's forces are (their capability) and what they intend to do with that strength (their intention). I will focus exclusively on the capability side for this summary, as in my thesis. Any arguments that you see written here have primary and/or secondary sources to back them up. I have read literally thousands of American naval and military attaché reports (and other random stuff, like British intelligence intercepts from the London Naval Conference), along with all sorts of books, journal articles, etc.
You are free to ask me questions about specific points and I will expand on them as much as possible. This first post is intentionally broad as it is intended as short summary, since I don't want to rewrite my entire thesis, and you folks certainly wouldn't want to read the whole darn thing. Due to the forum rules governing image size, a lot of my images are only direct links. With that said, here we go.
Example of a typical naval attaché report (WARNING Large Photos)
Spoiler : :
Air Power in the 1920s
Spoiler : :
The development of Japanese air power was extremely easy for American observers to track throughout the 1920s. Japan was new to the air power game, and as such it was heavily dependent on foreign assistance. The Imperial Japanese Naval Air Service (IJNAS) was trained by the British in 1921-1922, and the Imperial Japanese Army Air Service (IJAAS) was trained largely by the French. Foreign experts and technology were extremely prevalent throughout the 1920s, and made the tracking of Japanese aircraft, aerial tactics and industrial techniques simple because they weren't Japanese to begin with. Since all aircraft and engines were either produced under license in Japan or directly imported from other countries, including the United States, there was no shortage of accurate technical information for American observers to send back to Washington. This was made even easier as the Japan of the 1920s was a largely open society. Westerners were allowed to freely wander around the factory floors, tour air stations, small talk with personnel and observe Japanese flight operations up close. The naval attaché even regularly wrote letters to the Japanese Navy Ministry requesting detailed information about the IJNAS, and the Navy Ministry would respond truthfully, and in full!
Opinions of Japanese personnel, including pilots, were somewhat negative, but fair. These assessments were born out of direct observation of a fledgling air power which was reliant on foreign assistance. Westerners had trained many of Japanese personnel in the early 1920s, and continued to observe Japanese progress throughout the decade. Mechanics and other ground crews were generally viewed as competent, though somewhat poor at handling the newest technology. Japanese pilots were also seen as competent, though inexperienced and lacking in initiative. All Japanese personnel in the air services were considered slightly inferior to those found in the west. What may come as a surprise to some of you is that racism was almost entirely absent from reporting. Intelligence officers were professionals, and while ethnocentrism and so-called "national characteristics" would surface, they had no impact on the actual conclusions of the vast majority of reports in the 1920s. However, one correct conclusion born out of this decade would come to define American reporting later on despite its increasing inaccuracy. This was the belief that the Japanese were largely incapable of innovating in the realm of air power.
As would be the case throughout the interwar years, the main emphasis of American reporting was on the strategic and economic spheres. For every technical or tactical report, there were several which talked about Japan's industrial weakness. In short, Japan didn't have enough of anything, and the Americans knew it. Skilled labour? Not enough. Raw materials of virtually every description? Not enough. Machine tools? Not enough. Pilots? Not enough. Aircraft? Not enough. These were all issues which American observers addressed in their reports. In other words, the Americans were assessing not just Japanese air power's technology and tactics, but its ability to wage the kind of industrialised, protracted air war that the Americans intended to fight. This is a very important point, as it was the only feature of American reporting concerning Japanese air power which remained consistently correct and, ultimately, it was what ended up mattering the most.
Summary of Reports:
Technology and Tactics: Accurate
Personnel: Accurate
Industrial Strength and Strategic Issues: Accurate
Air Power from 1930-1937
Spoiler : :
Problems in American assessments began to arise in the early and mid 1930s. This was very much a transition period between the openness of Japanese society, and the reliance of its air services on foreign assistance that characterised the 1920s, and the extreme secrecy and independence of its air services which would come in the late 1930s. The 1930 London Naval Conference changed the entire trajectory of Imperial Japan. It was the last meaningful gasp of Japan's moderates, before the hard liners and militarists virtually seized control of the country. It also had a profound impact on the development of the IJNAS. In the 1920s, the Imperial Japanese Navy (IJN) had turned to light fleet units (cruisers, destroyers and submarines) in order to overcome their numerical disadvantage institutionalised in the Washington Naval Treaty. However, with the signing of the London Naval Treaty, these avenues of development were removed as effective options. What was left outside the bounds of the Washington Treaty System? Something that could help whittle down the American Pacific Fleet as it attempted to move across the Pacific? Aircraft. The amount of funds the IJN allocated to the development of its air power exploded right from the signing of the London Naval Treaty. Around the same time, the Imperial Japanese Army (IJA) began to take its air power a lot more seriously as well, and this shift in attitude did not go unnoticed.
American observers had open access to the budgets of the Japanese military, because debates within the diet regarding the allocation of funds was public information. The Americans knew the Japanese military was taking its air services far more seriously, but it was becoming difficult to see exactly what was going on. Open sources became common in American reporting on air power, as the traditional sources of information, such as tours of air stations, became increasingly less informative. Tours of air stations and factories were a regular occurrence from 1920-1937. However, in the 1930s, westerners were viewed with suspicion, and treated like spies. This was not unwarranted, as most civilians sent to help out at Japanese aircraft firms were tasked by the Office of Naval Intelligence (ONI) or Military Intelligence Department (MID) to report their findings. As the 1930s progressed, reports on Japanese air stations contained less meaningful information, and instead complained bitterly about the secrecy of their Japanese hosts. In short, the Americans had been spoiled by Japan's openness in the 1920s, and assumed that this trend would continue. Instead, they were met with this:
The most striking case of Japanese paranoia came from the experience of Mr. Bertrandias of the Douglas Aircraft Company, who stayed in Japan from December 1936 to February 1937. Despite the length of his stay, Bertrandias had little information to provide in his interview. Most of the report detailed the Japanese distrust of his intentions and the tightness of security measures. His visit was intended to conduct and oversee test flights of a Douglas Aircraft Company flying boat delivered to Japan. Most of the test flights Bertrandias observed were conducted at low altitude over short distances. Bertrandias flew the aircraft on the one flight of any distance, from Kobe to Fukuoka, but was not given any maps and did not know the destination until well into the flight. He was given various courses to fly, with the obvious intention of avoiding over-flights of sensitive areas, particularly around the Kure shipyards. Once the aircraft arrived near the Straits of Shimonoseki, Bertrandias was ordered to fly overland, well south of the Straits, toward a cloud-covered mountain range. He refused to do so as he had no knowledge of the mountains, and did not want to risk hitting a peak in the clouds. When his Japanese minders argued with him, Bertrandias decided to land directly in the Straits with the intention of talking the matter over further and, if necessary, moving through the forbidden zone on the surface rather than the air. This action visibly shook the Japanese on board, who talked about the trouble this approach would cause with the gendarmerie. Their concerns were validated when the flight was redirected to Beppu and the internal security services interrogated the Japanese members of the party. The Americans were not questioned, but the Japanese press later played up the incident, stating that an American representative had deliberately broken the law with possible “ulterior motives.” After this incident, Bertrandias was barred from seeing anything of importance.
Japanese military aviation had been virtually an open door for intelligence gathering in the 1920s, but the opening gradually narrowed through the early 1930s, and slammed shut with the start of the war in China in 1937.
This secrecy understandably led to a gradual drop in the quality of American intelligence regarding the development of the Japanese air services' technology, since this same period was the time when Japan began to develop its first generation of indigenous aircraft. Remember how dependent the Japanese had been on foreign assistance in the 1920s? Well, as they moved away from this dependence, American observers refused to acknowledge that the Japanese could innovate. In the study of intelligence, this is referred to as a "preconceived notion." What had been a true assessment based on real observations in the 1920s, gradually became less and less accurate as time went on. At the same time, American assessments got more and more wedded to the idea that the Japanese could not innovate. Information which indicated the Japanese air services were moving away from their dependence on foreign assistance was downplayed or ignored, and anything which indicated they were still copying western designs and techniques was often check marked, underlined and taken at face value. In other words, American intelligence began to develop a bad case of confirmation bias. It is telling that the only report which came out of the American naval attaché's office in Tokyo from 1930-1937 which highlighted the growing independence of the Japanese air services was a translation of a 1934 Soviet book by D. Streshnevsky (the book was two years old by the time the naval attaché sent it back).
Opinions of Japanese air and ground crews varied wildly from praise to derision and everything in between. Any attempt to make a coherent and singular view would produce a generic answer of little practical use. This situation may have stemmed from continual change and expansion within the Japanese air services, along with a decrease in the opportunity to regularly observe Japanese personnel. Whatever the root causes, the lack of a clear and consistent snapshot of Japanese personnel would become a major problem in the late 1930s. Observers would skip over the muddled reporting of the early 1930s and instead rely increasingly on the negative, and badly outdated, assessments of Japanese personnel from the 1920s.
What of American industrial and strategic-level assessments? They were consistently great. All together now: In short, Japan didn't have enough of anything, and the Americans knew it. Skilled labour? Not enough. Raw materials of virtually every description? Not enough. Machine tools? Not enough. Pilots? Not enough. Aircraft? Not enough. They weren't going to win a protracted air war with the United States. Here is a 1936 summary from the military attaché in Tokyo regarding the Japanese air services in a time of war:
In time of war, Crane believed the weakness of Japanese air power would be in planes and pilots. Japanese aircraft manufacturing, which already struggled with a lack of skilled workmen, would be hindered even more after the outbreak of hostilities due to the need for expanded production while making use of the same limited pool of manpower. Additionally, Japanese industry easily could be deprived of the raw materials needed to manufacture aircraft of quality and quantity...Crane did not dismiss Japanese power, and agreed that the IJAAS and IJNAS would pose a challenge in the short term. He simply noted that Japan could not win a full-scale and prolonged air war with the United States. Pilot reserves barely met peacetime demands, meaning that Japan’s core of trained aircrew would be depleted rapidly through wartime attrition. Thus, the Japanese would shorten their pilot instruction times significantly in order to replace their losses, and send poorly trained and inexperienced aircrew into frontline service with predictable results.
Summary of Reports:
Technology and Tactics: Poor
Personnel: Confused and Contradictory
Industrial Strength and Strategic Issues: Accurate
Air Power from 1937-1941
Spoiler : :
American assessments of Japanese air power in the late 1930s and into the war were badly flawed at the lower levels. Japanese secrecy was extreme. Tours of air stations and factories virtually disappeared. As a result, reporting became heavily dependent on open sources, like aviation magazines and newspaper articles. These sources were stuck in the mindset of the 1920s and early 1930s, when Japan was dependent on foreign support to develop their air power. The views of these sources remained accurate when they discussed Japanese industry, but American understanding of Japan's technology and tactics was scarce and largely out of date. The number of redundant and superfluous reports skyrocketed. Many did little more than paraphrase official Japanese press releases about the war in China, or provided information so vague that they might as well have said "it is possible that the Japanese air services are, in fact, using aircraft."
Due to the level of secrecy employed by the Japanese, this drop in the quality of reporting can be partially justified. However, this period also saw a dramatic increase in American observers' reliance on the preconception that the Japanese could not innovate, as well as an increase in the influence of ethnocentrism and "national characteristics." Many assessments concluded that Japanese personnel were inherently inferior because they were Japanese. This was not something commonly found in earlier reporting. The less information the Americans had regarding Japanese military aviation, the more they fell back on the old motif of unoriginality and negative views from the 1920s, with an increasingly harsh tone. Nowhere was this shift more evident than in the discussion of Japanese technological progress. The view that the Japanese could do little more than copy foreign designs was deeply entrenched, even as evidence to the contrary continued to pile up. This was typical of such reports at a time when Japan was fully independent in aircraft design and manufacturing:
http://i.imgur.com/33taq9U.jpg
Even when the Americans obtained accurate technical information about a specific aircraft, they failed to make the connection between it and the broader implication that Japan was producing good indigenous aircraft. The Chinese had captured a fully intact B5N1 carrier attack aircraft and conducted extensive flight tests. The results were then given to the Americans. The naval attaché sent the accurate technical data back, but entirely omitted the fact that the plane was clearly not a copy of anything. Therefore, a farcical situation arose where assessments like the one above coexisted with explicit evidence that directly contradicted those assumptions. Another example was the G3M, an IJNAS medium bomber (Japanese designated it "heavy"), which was old by this point, and was first identified by the Americans in late 1937. It was immediately assumed, without evidence, that the G3M was a copy of a German Ju-86 when, in fact, it was entirely indigenous and superior to the Ju-86 in every way. A later report concluded that the aircraft was a "copy of a Heinkel design." Interestingly, the Americans could never decide from which German aircraft company, or aircraft, the Japanese had supposedly copied their design of the bomber. The only consistent feature of American assessments was that it had to be a copy of something.
Numerous reports which detailed fictional aircraft also surfaced during the period, and regardless of how absurd the report was, aircraft which existed only in American imaginations were given corresponding European designs that the Japanese supposedly had copied. William D. Puleston, the Director of Naval Intelligence from 1934-1937, assumed, without evidence, in his 1941 book that contemporary American planes were faster, more maneuverable and better designed than their Japanese counterparts, partly because the Japanese lacked inventive capabilities. This assumption would last well into the war itself. The Ki-61-I, an IJAAS fighter, was given the Allied codename 'Tony' because, after it was first confused for a Bf-109 produced under license, the Americans assumed it was a copy of an Italian design due to its superficial European-style appearance. The plane was actually an indigenous design that only made use of a DB-601A inline engine produced under license.
"Japanese unoriginality" was included in almost every report from the period. Anything which contradicted this prevailing view was downplayed or ignored outright. All of Japan's main combat aircraft from the late 1930s onward were indigenous designs. Many of these aircraft had been observed, or test flown, and the information sent back in numerous reports. Yet American observers either misidentified them as foreign copies without evidence, or failed to make the connection between one example of a capable Japanese aircraft design and the wider implication that Japanese industry was self-sufficient, and producing first-rate aircraft. This view combined with strategic surprise and shaped the initial shock which surrounded the capabilities of the Japanese air services during the start of the war. A nation which was assumed to possess a large number of obsolescent foreign copies actually had entire fleets of indigenous aircraft that were roughly equivalent to their foreign contemporaries.
Detailed assessments of Japanese personnel became scarce, but had negative conclusions. After the indecision of the early and mid 1930s, American observers concluded that Japanese personnel were of poor quality when they entered the war with China. While that experience increased this level of competence, Japanese pilots and mechanics were viewed as inferior to their western counterparts. Chinese assessments of the skill of Japanese pilots were largely ignored due to American dismissal of the Republic of China Air Force. Deliberate improvements of Japanese aerial tactics were also ignored, and occasionally misinterpreted as incompetence. Ethnocentrism and "national characteristics" were all-pervasive in this reporting. The overall impression was that the Japanese air services had began the war in China poor, and their experienced had helped them improve to a level of second-rate mediocrity.
What of American industrial and strategic-level assessments? They were consistently great. All together now: In short, Japan didn't have enough of anything, and the Americans knew it. Skilled labour? Not enough. Raw materials of virtually every description? Not enough. Machine tools? Not enough. Pilots? Not enough. Aircraft? Not enough. They weren't going to win a protracted air war with the United States. The initial shock that the Japanese air services were technologically and tactically first-rate did not prove decisive despite strategic surprise increasing the impact of mistakes made in low-level assessments. Ultimately, the industrial and strategic weaknesses of Japan were the deciding factors in the conflict, something which the Americans had been predicting since the 1920s.
In the words of a much smarter man than myself:
Greg Kennedy notes that to view “low-level successes as demonstrative of the overall ability of Japan to manifest effective, modern air power is to misunderstand fundamentally the core attributes of air power.”
Summary of Reports:
Technology and Tactics: Awful
Personnel: Poor
Industrial Strength and Strategic Issues: Accurate
Naval Power from 1920-1941
Spoiler : :
http://pwencycl.kgbudge.com/images/A/k/Akatsuki__class_oni_full.jpg
The reason I will discuss naval power in one section, versus the three sections used for air power, is because American intelligence assessments of the IJN remained mostly consistent for the entire period. They never went through the radical shifts in quality that occurred with assessments of air power. Overall, assessments of the IJN could be described as "consistently mediocre." They never reached the dizzying heights of the 1920s assessments of air power, but also never reached the sickening lows of the air power assessments in the late 1930s. Part of the reason for this consistency in reporting was the Japanese were never as open with the progress of their fleet as they were with their air services. The IJN's surface fleet was virtually self-sufficient throughout the entire interwar period. Sure, they produced "such-and-such" knick-knack under license here or there, but it was out of convenience rather than necessity. Without a need for extensive foreign assistance, there was also no need to be so open about what their fleet was doing. One such example of the kind of Japanese secrecy regarding their fleet:
The Americans made liberal use of "mirror imaging" in their reporting of the IJN. If the motto of the assessments regarding air power was "if we don't know, assume they are worse than us." The motto of assessments regarding naval power was "if we don't know, assume they are probably about as good as us." American observers conducted a large amount of "bean counting," comparing the amount of available combat power in both navies, right down to the number of gun barrels and torpedo tubes. Of course, at the very heart of this type of analysis was the assumption that the technology of both navies was at worst roughly equivalent qualitatively, and at best the Americans had the advantage. The possibility that the Japanese could develop any tactic or technology which was superior to the Americans never crossed their minds. "Mirror imaging" was most accurately summarised by a comment in Puleston's 1941 book:
This was far from the case in reality, but such assumptions were not always disastrous. After all, it was much better to assume your opponent would be roughly as good as you, than to assume your opponent was far worse. The largest negative consequence of "mirror imaging" was when the two sides clashed in several night engagements off Guadalcanal. The Americans had badly neglected night training in the interwar years. Night manoeuvres were infrequent, heavily scripted and unrealistic. To say that the Americans had a pre-war night fighting doctrine is not entirely accurate, because it implies there was uniformity in training and tactical ideas. However, when the forces were thrown together under Rear Admiral Daniel J. Callaghan in order to stop the planned Japanese bombardment of Henderson Field in November 1942, the formation lacked a common understanding of how to engage an enemy at night. In sharp contrast, the Japanese had trained rigorously, possessed a firm night fighting doctrine, had an entire formation dedicated to such an action, and would give a good account of themselves as a result. They had the best night optics in the world, and many of their vessels had been designed with torpedo-centric night attacks in mind. The Americans had identified Japan's emphasis on night fighting before the war, but these warnings were ignored because there was an assumption that it was impossible for the IJN to be superior to their American counterparts in any endeavour.
American observers' assumption that their navy could not be surpassed by the Japanese was the driving force behind the refusal to acknowledge that the IJN was using torpedoes larger than 21", despite dozens of reports to the contrary. It would take until April 1943, over twenty years since they had been approved for usage in the IJN, for ONI to acknowledge that Japan was using 24" torpedoes. The Americans refused to acknowledge that the Japanese carried a large number of torpedo reloads on board their warships, and that most of their ships were capable of reloading them in combat. They also miscounted the number of torpedo tubes which the Japanese had on their cruisers. Overall, the Americans underestimated the number of torpedoes the Japanese could fire in a given engagement by over 100%. Of course, the quality of Japanese torpedoes was also ignored. The Americans used their own Mark XV as the benchmark for Japanese torpedo quality, while the Type 93 was superior in every way, even when the former managed to function at all. Now with this information in mind, look at that ONI assessment of the Fubuki-class at the top of this post.
However, "mirror imaging" did work when assessing the Japanese battle line. Sure, there were doctrinal differences between the two sides, but nothing so Earth-shattering that "mirror imaging" wasn't useful. The Americans did a good job of tracking the modernisation of Japan's old battle wagons. Generally, their assessments of displacements were off by several thousand tons, but the capabilities of the ships were largely known. The most notable error in the assessments of Japan's aging battle line was the speed of the Kongo-class fast battleships, which remained unknown until the midst of the Guadalcanal campaign (they assumed 26 knots). Overall, the Americans had all the information they needed regarding the older battleships through simple "bean counting." People can bicker about the quality of armour, shell penetration values, fire control, etc. until they are blue in the face. At the end of the day, Japan's old battleships were roughly equivalent to the United States' old battleships from similar eras, except the Americans had more of them and then some. This was the ultimate conclusion of American observers at the time.
Now, I can see some of you getting antsy about a certain 71,000 ton elephant in the room. I'm not going to get into extreme detail regarding the Yamato-class since I feel the story is pretty well known (unless you want me to add more). They were designed and constructed under an insane amount of secrecy. One of the most important acts of deception was hiding the money required for construction behind a number of fictitious destroyers in the budget submitted to the diet, as the Americans used debates in the diet as a major source for determining the IJN's order of battle. The confusion regarding the rumoured battleships would last through to the end of the Second World War. As late as December 1944, the Yamato-class were listed in ONI's identification and technical handbook at 9x16" guns and 45,000 tons. Here is one amusing anecdote about the Yamato-class from the late 1930s:
I was going to include the examples of the Mogami-class cruisers and aircraft carriers in this post, but this section is already extremely long. Therefore, I will leave them out unless I'm asked.
Assessments of Japanese naval personnel were largely positive, but often mentioned what the Americans viewed as a lack of ocean-going experience. The most frequent conclusion in reports which concerned Japanese personnel was a lack of initiative. In many cases, such criticism was mostly unfounded. Instead, it relied on assumptions about the Japanese people. Stuff like this was common (though usually not as negative):
What about operational, strategic and industrial-level issues? They were all great. The Japanese openly detailed and bragged about their interception-attrition operations, so the generalities of the IJN's operational and strategic concepts were known to the Americans well before the war. As for industry? Well. I won't bother copy/pasting what I have said previously. The Americans knew Japan didn't have what it needed to fight them over the long term, hence why War Plan Orange's final form was a slow, methodical advance toward the Home Islands. In the end, these broader assessments mattered more than missing certain technical issues. Sure, not have a good understanding of Japanese night fighting and torpedo warfare capabilities hurt in the short term, but in the end Japan was ground to dust fighting an enemy that was, to many Japanese decision makers, incomprehensibly wealthy, industrious, rich in natural resources and determined. This is the real main underlying point. The Americans did not just blindly stumble into being a nearly indestructible, massive war machine. They actively planned for, and assessed their possible enemies, with this important assumption in mind.
Here is a quote from yet another man smarter than myself. It can easily be applied to American assessments of Japanese naval power as well:
Summary of Reports:
Technology and Tactics: Poor
Personnel: Mediocre
Industrial, Operational and Strategic Issues: Accurate
The reason I will discuss naval power in one section, versus the three sections used for air power, is because American intelligence assessments of the IJN remained mostly consistent for the entire period. They never went through the radical shifts in quality that occurred with assessments of air power. Overall, assessments of the IJN could be described as "consistently mediocre." They never reached the dizzying heights of the 1920s assessments of air power, but also never reached the sickening lows of the air power assessments in the late 1930s. Part of the reason for this consistency in reporting was the Japanese were never as open with the progress of their fleet as they were with their air services. The IJN's surface fleet was virtually self-sufficient throughout the entire interwar period. Sure, they produced "such-and-such" knick-knack under license here or there, but it was out of convenience rather than necessity. Without a need for extensive foreign assistance, there was also no need to be so open about what their fleet was doing. One such example of the kind of Japanese secrecy regarding their fleet:
During the 1927 grand fleet manoeuvres, American destroyers deliberately steamed into the path of the Japanese force in an effort to gather as much intelligence as possible. As they neared Akagi, her escorts interposed themselves and laid a smokescreen to conceal flight operations. A similar event occurred in 1934, when a division of American destroyers accidentally found itself in the midst of an IJN exercise. As they made their way between the light forces and the battle line they were overtaken and harassed by several warships, including the flagship of the Japanese force. Despite these disruptions, the Americans saw two aircraft carriers operating together. The carriers’ plane guard destroyers immediately laid smoke in front of their charges in an attempt to prevent any observation. However, the commander of the American destroyers decided to seize the initiative and steamed through the smokescreen. He observed several landings, which went “very well” and also noted that these operations had been carried out in poor weather “with apparent ease and safety.” In the conclusion of the report, the American commander described the actions of the Japanese, and the laying of smoke in particular, as “most discourteous.”
The Americans made liberal use of "mirror imaging" in their reporting of the IJN. If the motto of the assessments regarding air power was "if we don't know, assume they are worse than us." The motto of assessments regarding naval power was "if we don't know, assume they are probably about as good as us." American observers conducted a large amount of "bean counting," comparing the amount of available combat power in both navies, right down to the number of gun barrels and torpedo tubes. Of course, at the very heart of this type of analysis was the assumption that the technology of both navies was at worst roughly equivalent qualitatively, and at best the Americans had the advantage. The possibility that the Japanese could develop any tactic or technology which was superior to the Americans never crossed their minds. "Mirror imaging" was most accurately summarised by a comment in Puleston's 1941 book:
It is apparent that a naval campaign in the western pacific would be a clash of two well-prepared navies, with ships of the same types, organized in similar formations, trained along similar lines, imbued with similar tactical ideas.
This was far from the case in reality, but such assumptions were not always disastrous. After all, it was much better to assume your opponent would be roughly as good as you, than to assume your opponent was far worse. The largest negative consequence of "mirror imaging" was when the two sides clashed in several night engagements off Guadalcanal. The Americans had badly neglected night training in the interwar years. Night manoeuvres were infrequent, heavily scripted and unrealistic. To say that the Americans had a pre-war night fighting doctrine is not entirely accurate, because it implies there was uniformity in training and tactical ideas. However, when the forces were thrown together under Rear Admiral Daniel J. Callaghan in order to stop the planned Japanese bombardment of Henderson Field in November 1942, the formation lacked a common understanding of how to engage an enemy at night. In sharp contrast, the Japanese had trained rigorously, possessed a firm night fighting doctrine, had an entire formation dedicated to such an action, and would give a good account of themselves as a result. They had the best night optics in the world, and many of their vessels had been designed with torpedo-centric night attacks in mind. The Americans had identified Japan's emphasis on night fighting before the war, but these warnings were ignored because there was an assumption that it was impossible for the IJN to be superior to their American counterparts in any endeavour.
American observers' assumption that their navy could not be surpassed by the Japanese was the driving force behind the refusal to acknowledge that the IJN was using torpedoes larger than 21", despite dozens of reports to the contrary. It would take until April 1943, over twenty years since they had been approved for usage in the IJN, for ONI to acknowledge that Japan was using 24" torpedoes. The Americans refused to acknowledge that the Japanese carried a large number of torpedo reloads on board their warships, and that most of their ships were capable of reloading them in combat. They also miscounted the number of torpedo tubes which the Japanese had on their cruisers. Overall, the Americans underestimated the number of torpedoes the Japanese could fire in a given engagement by over 100%. Of course, the quality of Japanese torpedoes was also ignored. The Americans used their own Mark XV as the benchmark for Japanese torpedo quality, while the Type 93 was superior in every way, even when the former managed to function at all. Now with this information in mind, look at that ONI assessment of the Fubuki-class at the top of this post.
However, "mirror imaging" did work when assessing the Japanese battle line. Sure, there were doctrinal differences between the two sides, but nothing so Earth-shattering that "mirror imaging" wasn't useful. The Americans did a good job of tracking the modernisation of Japan's old battle wagons. Generally, their assessments of displacements were off by several thousand tons, but the capabilities of the ships were largely known. The most notable error in the assessments of Japan's aging battle line was the speed of the Kongo-class fast battleships, which remained unknown until the midst of the Guadalcanal campaign (they assumed 26 knots). Overall, the Americans had all the information they needed regarding the older battleships through simple "bean counting." People can bicker about the quality of armour, shell penetration values, fire control, etc. until they are blue in the face. At the end of the day, Japan's old battleships were roughly equivalent to the United States' old battleships from similar eras, except the Americans had more of them and then some. This was the ultimate conclusion of American observers at the time.
Now, I can see some of you getting antsy about a certain 71,000 ton elephant in the room. I'm not going to get into extreme detail regarding the Yamato-class since I feel the story is pretty well known (unless you want me to add more). They were designed and constructed under an insane amount of secrecy. One of the most important acts of deception was hiding the money required for construction behind a number of fictitious destroyers in the budget submitted to the diet, as the Americans used debates in the diet as a major source for determining the IJN's order of battle. The confusion regarding the rumoured battleships would last through to the end of the Second World War. As late as December 1944, the Yamato-class were listed in ONI's identification and technical handbook at 9x16" guns and 45,000 tons. Here is one amusing anecdote about the Yamato-class from the late 1930s:
The secrecy which surrounded the construction of the battleships paradoxically worked to increase American suspicions that they were larger than 35,000 tons. In June 1939, Hanson Baldwin, the naval correspondent for the New York Times, wanted to get a statement from the Japanese that they were not building battleships that were 45,000 tons or larger. He was against the United States building its own expensive monsters, and therefore wanted a Japanese statement to use as ammunition to shut down the USN’s ambitions. The request for information was sent to the Japanese Navy Ministry and the reply came back that the IJN could not confirm nor deny that Japan was constructing “super-battleships.” The New York Times Tokyo correspondent was told that certain officers in the IJN were willing to state definitely and in writing that Japan was not building, and would never build, “super-battleships.” However, they were overruled by the Navy Minister. On another occasion, an IJN spokesman denied that Japan was building any ships “of 40,000 or 45,000 tons.” This was technically correct, and one of the Japanese admirals present “was unable to suppress a smile.”
I was going to include the examples of the Mogami-class cruisers and aircraft carriers in this post, but this section is already extremely long. Therefore, I will leave them out unless I'm asked.
Assessments of Japanese naval personnel were largely positive, but often mentioned what the Americans viewed as a lack of ocean-going experience. The most frequent conclusion in reports which concerned Japanese personnel was a lack of initiative. In many cases, such criticism was mostly unfounded. Instead, it relied on assumptions about the Japanese people. Stuff like this was common (though usually not as negative):
[The Japanese naval officer] fears responsibility and is reluctant to assume it. This is due to his superficial knowledge of most subjects and his consequent lack of self confidence...The Japanese as a people are superficial and shallow and they almost never thoroughly master any subject, since they lack application and are led by pride and conceit and the fear of being thought slow or stupid to declare they understand a subject long before they do...The Japanese originate practically nothing. They are almost entirely lacking in the inventive faculty. Even as copyists they almost invariably produce a distinctly inferior article.
What about operational, strategic and industrial-level issues? They were all great. The Japanese openly detailed and bragged about their interception-attrition operations, so the generalities of the IJN's operational and strategic concepts were known to the Americans well before the war. As for industry? Well. I won't bother copy/pasting what I have said previously. The Americans knew Japan didn't have what it needed to fight them over the long term, hence why War Plan Orange's final form was a slow, methodical advance toward the Home Islands. In the end, these broader assessments mattered more than missing certain technical issues. Sure, not have a good understanding of Japanese night fighting and torpedo warfare capabilities hurt in the short term, but in the end Japan was ground to dust fighting an enemy that was, to many Japanese decision makers, incomprehensibly wealthy, industrious, rich in natural resources and determined. This is the real main underlying point. The Americans did not just blindly stumble into being a nearly indestructible, massive war machine. They actively planned for, and assessed their possible enemies, with this important assumption in mind.
Here is a quote from yet another man smarter than myself. It can easily be applied to American assessments of Japanese naval power as well:
Christopher Bell states that “British naval intelligence [regarding the Japanese] is often presented as a matter of incompetence leading to disaster, but it is better seen as a case of mediocrity leading nowhere at all.”
Summary of Reports:
Technology and Tactics: Poor
Personnel: Mediocre
Industrial, Operational and Strategic Issues: Accurate
They'll choose prejudice over precedence, every time.
