Call it revisionism, but Day Of Deceit: The Truth About FDR and Pearl Harbor, by Robert Stinnett, and Pearl Harbor: The Seeds and Fruits of Infamy, by Percy L. Greaves Jr. make a worthy case that FDR and his associates knew of the impending attack on Pearl Harbor. Most likely, they expected the attack to be easily repulsed, unaware of the combat strength of Japanese naval aviation and of the lack of defensive readiness at Pearl.
Although the extent and reason for the tactical surprise that Japan achieved at Pearl Harbor remain disputed, Japan's strength and daring clearly were a strategic surprise for the US -- a development that FDR and his associates must take the blame for. They underestimated Japan's potential as an adversary and the US paid heavily for that error.
Notably, with pertinent intelligence files in US and British archives still secret, the case for a revisionist view of the Pearl Harbor attack cannot be definitively rejected. Let us hope that we both live long enough to be around when those files are finally released to public view and the issues addressed on a more informed basis.
Until presented proof otherwise, I’ll maintain for those saying FDR, George Marshall and Cordell Hull had a unique foreknowledge of a Pearl Harbor attack requires looking backwards and piecing together specific data points to prove their thesis. They have had to ignore the fact that these men were living out history forwards. The information the country received from traffic analysis, informants, investigations, and code braking swam in a sea of 10,000’s of data points each month. Remember a few years ago you could buy pictures that seemed a mass of random color pixels, but a single picture emerged if you stared at it in the right way? In this case a host of pictures emerged each week. To make some sense of this data it had to fit probable alternatives.
The population of the probable (in the fall of 1941 we had too few resources to deal with the possible as well) had to fit into War Plan Orange and the corresponding Japanese plan, which was generally known to the U.S. Both plans envisioned the supreme naval battle would be fought in the Western Pacific. Both navies were disciples of Alfred Thayer Mahan who wrote the outcome of war at sea would always be decided by the “decisive naval battle”. Past history had borne that out at Trafalgar, Tsushima, and Jutland. For Jutland Churchill said, “Jellicoe was the one man who could have lost the war in an afternoon”.
When Yamamoto proposed his radical departure from Japanese strategic principles only his firm commitment to resign at a meeting in October 1941 sealed the deal. The Naval General Staff could either find a new commander of the fleet at this late date, or accept his radical departure from existing plans.
In this country Plan Orange continued to determine the most probable interpretation to place on intelligence and events. That may have been an important factor for ignoring the implication of the data point called the “bomb plot” message. In September 1941 the U.S. decrypted a message sent to the Japanese Honolulu consulate asking for reports of ships anchoring or tying to wharves in five specific areas. Some thought this a departure from the ordinary while others thought this a normal interest in ship movements that could help them understand how quickly the fleet could sortie for that “decisive naval battle”.
It seems that only after the war started were men appreciated who could think outside normal channels. In the Pacific I think of men like Nimitz, Rochefort, and Doolittle.