Why did the intelligence system apparently fail to forewarn the American government of the attack on Pearl Harbor?

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313 HIS        -  -        Corina Meyer

Why did the intelligence system apparently fail to forewarn the American government of the attack on Pearl Harbor?

“Why, with some of the finest intelligence available in our history, with the almost certain knowledge that war was at hand, with plans that contemplated the precise type of attack that was executed by Japan on the morning of December 7th – why was it possible for Pearl Harbor to occur?”

Report of the Congressional Inquiry, 1946

The attack on Pearl Harbor on December 7, 1941 raises some fundamental questions regarding American Intelligence at that time. The Intelligence system was sufficiently developed by 1941, with the breaking of the Japanese encoding device which is referred to as Purple, and an abundance of broken codes and signals received during the few weeks leading up to Pearl, which should have served as a serious warning to Intelligence that an attack was about to take place. Why is it then that Intelligence failed to recognise the signs and dismissed them as irrelevant?

There are several explanations for this, the first being the largely discussed conspiracy theory, which claims that President Roosevelt withheld vital information from responsible officers, thus keeping the Pacific Fleet in Hawaii open for attack, with the intention of U.S. involvement in the European War. Roosevelt knew it would be impossible to obtain support for war from Congress, and it was obvious that Germany had no intention of declaring war on America. His only alternative was war with Japan, which in turn would constitute a war with Nazi Germany.

The attack could be provoked by increasing hostilities with Japan. Roosevelt provided continued financial and military aid to China, Britain, and the Netherlands, alongside a freezing of Japanese assets and trade in July of 1941, only a few months before the surprise attack. Naval advisors had stated it was not advisable to retain the Pacific Fleet in Hawaii, but President Roosevelt objected to their advice, proclaiming it was necessary to keep the Fleet at their present position to restrict Japanese aggressions in the Far East. However, as Roosevelt was well aware, the hard truth was that the Fleet in Hawaii did not contain adequate power necessary to influence Japanese actions as a Fleet in the Far East would have done. It was obvious that the Pacific Fleet in Hawaii would need a considerable amount of increased strength to protect itself under attack, let alone have any influence over actions in the Far East. Instead of increasing its strength, Roosevelt authorised decisions to weaken the Pacific Fleet in Hawaii, including the removal of three battleships, an aircraft carrier, and several cruisers amongst other essential materials.

The alliance between Japan and Germany provided Roosevelt with an opportunity to involve the U.S. in the war without having to declare war himself and without having to gain consent from Congress or the public. He therefore followed an unrealistic foreign policy toward Japan in order to tempt Japan into an attack, an attack to which he had so kindly guaranteed them a success. An act of aggression on Pearl Harbor for instance, would result in much greater success than an attack against a Fleet based on the American West Coast. The measures taken in March of 1941 to reduce the strength of the Fleet at Pearl only provided the Japanese with more incentives.

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Further evidence supporting the conspiracy theory lies within information received from decodes and the termination of the Washington Conference in November of 1941. The Japanese had made it clear to Roosevelt that this termination would lead to war with the United States and Great Britain. Roosevelt was also aware of Japan’s military history, and their reputation of entering a war with a surprise attack. Shocking evidence of messages received by Intelligence warning of an attack on Pearl Harbor, further support the conspiracy theory. The messages were intentionally kept from responsible officers of the Pacific Fleet at Hawaii in order ...

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