The Intelligence Failure At Pearl Harbor

Collection or Analysis Failure ?

The Intelligence failure At Pearl Harbor was one not of analysis, as Wohlstetter implies, but of collection.1

There is no doubting the fact that there was an American intelligence failure in December 1941, as the Japanese Pacific Fleet managed to cross the Pacific and attack the American Fleet based at Pearl Harbour without being intercepted or even detected. The question remains as to whether the American failure was one of collection or analysis and this is a point which David Kahn and Roberta Wohlstetter come to very different conclusions about. Whilst Kahn advocates the view that the American failure was due to a lack of available intelligence to be collected, Wohlstetter in 1962 stated her belief that there was enough relevant intelligence to point to the fact that the Japanese Fleet was on its way to attack Pearl Harbour and that the error was in analysis, which overlooked this relevant intelligence, due to ‘background noise’ Firstly I shall examine Kahn`s views in detail and then mention briefly the opposing arguments, such as Wohlstetter`s thesis and the conspiracy theories. The inevitable conspiracy theories about Pearl Harbor, whilst very interesting, have the tendency to fall apart at the seams when analysed closely in relation to the facts. These include Russbridger and Nave`s book, ‘Betrayal At Pearl Harbour’ which claims that the Britain knew about the Pearl Harbour attack and didn't inform Roosevelt in order to trick him into the war when the Japanese attack came; the claim by captain Safford that ‘East Wind Rain’ (the Japanese code for an imminent attack on America) was sent and intercepted on 3rd December. There is also Brian Garlfields 1981 ‘factual’ Novel that subtly claims the British knew the whereabouts of the Japanese Fleet, due to a sighting by a Dutch Submarine somewhere in the Pacific and lastly the claim that Roosevelt knew about the coming attack, but ignored it in order to force the isolationist congress and public into the Second World War.

Christopher Andrews refers to disorganised and under resourced U.S intelligence community2 in 1941 and like Kahn, comes to the conclusion that with MAGIC (the Japanese diplomatic code broken in September 1940) and traffic analysis, there was not enough intelligence available to successfully detect the Japanese fleet or its intentions. Kahn states that Only one form of intelligence appeared to offer relatively solid information about Japanese naval matters: traffic analysis.3 Kahn continues by stating that there was no significant HUMINT (Human Intelligence) as the United States had no spies anywhere in the world4 or SIGINT (Signals Intelligence) other than traffic analysis and MAGIC, which still, were not going to yield any relevant information concerning top secret Japanese Naval plans. Altogether America could have had no idea that the Japanese Fleet was about to attack Pearl Harbor, due to the lack of intelligence. Kahn refers to the insufficiency of cryptanalysts5 as Americas greatest blunder at Pearl Harbor, as there was a severe lack of interest, investment and co-ordination in the intelligence service. Indeed in 1929 the Secretary Of State, Henry L. Stimpson closed the cryptanalysis agency as he believed gentlemen do not read each others mail6 which left only the under funded Naval and Army cryptanalysis units that worked on a competitive and definitely in-efficient manner by adopting a odd and even day system between the Army and Navy units. There was little ability to collect intelligence on Japan as the means were not available, Kahn argues convincingly. What Kahn is saying is that Roberta Wohlstetter is wrong in saying that analysis was the fault, because there was nothing to analyse! Christopher Andrews in his book “For The Presidents Eyes Only”, reinforces Kahns argument by stating that Americans simply didn't expect an attack on Pearl Harbour, because it was thought technically impossible, and also because America was blinded by a racism that led the Americans to underrate Japanese abilities and will7 Americas military and political leaders thought Japan incapable of successfully executing a precise plan aimed at tactical surprise against the United States of America. This racial element coupled with the misguided assumption that Pearl Harbour was safe from attack, left America unsuspecting and limited as far as military intelligence on Japan was concerned. Whilst Kahn states that you rarely find what you are not looking for Andrew points to the fact that Roosevelt was; and although looking, was not necessarily expecting in the right place. Kahn ends his article by talking about the legacy of Pearl Harbor, and concludes that Pearl Harbor has taught the United states to gather more information and to evaluate it better8

The Japanese Carrier Fleet observed radio silence whilst on its way to its target, and only the elite Japanese Naval officers knew of the attack (i.e. not the Japanese embassy in Washington), so with the limited intelligence sources America had it was impossible to detect the fleets movements or intensions. In 1941 the American traffic analysts lost track of the Japanese Fleet twice and it was assumed that the Fleet was in home waters using short wave radio signals, which turned out to be a correct assumption concerning the fist case, but not the latter where the Japanese Carrier Fleet was actually attacking Indo-China. Christopher Andrew states the important point that Roosevelt was expecting an attack as early as November 25th 1941, when he addressed hi s war cabinet, which seems to point to the fact that America should have been looking very hard for the Japanese Pacific Fleet when it ‘disappeared’ in late 1941. Andrew agrees with Kahn`s thesis in saying “ But if U.S intelligence failed to detect the first target of the Japanese attack, it provided clear evidence that war was on the way.9 The American political and military leadership were expecting an attack in the Philippines or the Panama Canal rather than Pearl Harbor which the Americans believe d to have too shallow water for a conventional torpedo strike. Andrew, like Kahn, concludes that if breaking the Japanese Naval ciphers had been given higher priority then America would have broken the JN25b cipher and seen the attack on Pearl Harbor coming. Therefore both Kahn and Andrew argue very convincingly that it was a failure of collection not analysis, that led to America being totally surprised by the Japanese attack on Pearl Harbour. Another factor that solidifies Kahn’s argument is that he had access to released intelligence documents that Wohlstetter didn't, making his sources more complete and accurate than that of Wohlstetter`s in 1962. In Wohlstetters defence, it is also true that the Japanese 14 part terms of rejection that was sent to Washington helped towards the four important MAGIC (Japanese Diplomatic code) deciphers, that contained messages from Tokyo to the Japanese embassy in Washington, to destroy all documents and cipher machines i.e. war was imminent. This was a failure of analysis as the MAGIC decrypts were collected, but the ludicrous intelligence system that America adopted to decipher, analyse and deliver its decrypts meant that it was at the point of analysis that the failure was made. The conspiracy theories concerning the attack on Pearl Harbor in December 1941, all contain flaws that undermine their own claim. For instance, Rusbridger and Nave`s book “Betrayal At Pearl Harbour”, is littered with claims that are easily disproved when the facts are referred to or as Kahn puts it several flaws destroy this theory.10 Nave's claim that, whilst he was a code breaker for the British in Australia, the Jn25b Japanese Naval code was broken before the attack on Pearl Harbor, is rebuffed when it is realised that he had left Australia a year previous to the attack on Pearl Harbor. This particular conspiracy theory is fatally flawed due to the fact that Churchill wouldn't have withheld information from the Americans in order to draw them into the Pacific war against Japan as he wanted America in Europe to help Britain fight Germany much more. Brian Garfield`s Novel, ‘Palladin’, apparently based on real facts and characters, suggests again that the British knew about the Japanese attack fleet an d withheld the information from Washington. The story goes, that a Dutch submarine spotted the fleet in the Pacific and reported it; the news eventually reaching London who decide to blow the Submarine up to cover up, whilst not telling Washington of the obvious Japanese intentions. Again the theory is flawed by Churchill's real priorities being in Europe rather than Asia, not to mention the author admits that the book is ‘based’ on the facts, rather than being an entirely true story, which leaves its validity in a study of history as doubtful to say the least. However the novel does raise the question; how did the 6 carrier strong fleet manage to travel all the way across the busy Pacific without a sighting ? Nevertheless the fact remains that Churchill would not have withheld information regarding the attack on Pearl Harbor from Roosevelt, as he wanted America in Europe not Asia. Captain Safford's conspiracy theory is particularly interesting as it frames Roosevelt as the one withholding information. Stafford says that the “East Wind Rain” code was sent by the Japanese around the 4th December, and a ‘higher authority’ removed these decrypts and he goes on to say that Roosevelt knew of the attack, but didn't react in order to have the isolationist American people and the senate shocked into war. This theory is also inherently flawed as Even if Roosevelt had wanted to go to war, he would not have wanted to enter it with his fleet badly weakened. 11

Above all, Kahns argument is much more water tight than that of Wohlstetter and very well argued allying the relevant facts with his argument. The conspiracy theories do not counter his argument, but offer various reasons for his conclusion; that there w as no intelligence available to indicate that a Japanese attack was coming, let alone where, but on close analysis they can be seen as The facts as we can see them certainly seem to advocate Kahn’s thesis as little intelligence was available to Washington, which was because intelligence service was under rated and therefore under funded. However, Christopher Andrew does highlight the fact that the Americans were severely disadvantaged by their racial prejudices which blinded them, leading to a fatal underestimating of Japanese capabilities. the failure was indeed one of collection as America's lack of investment and faith in intelligence led to a lack of information on Japanese Naval matters and the failure of the United states to detect the Japanese attack on Pearl Harbor. The simple answer is that the intelligence, good although it was in certain areas, was not good enough.12


1. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 148

2. Christopher Andrew, For The President’s Eyes Only. Page 75)

3. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page144

4. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 141

5. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 144

6. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 139

7. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 145

8. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 152

9. Christopher Andrew, For The President’s Eyes Only. (Page 113)

10. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 149

11. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 150

12. David Kahn, The Intelligence Failure Of Pearl Harbour, Foreign Affairs (Fall 1991) Page 148


Mail Me