I have not so far read any of the books upholding that theory, so my opinion on this cannot be objective for want of information. From what I do know about the attack as such however I do agree with F-22's estimation.
Germany rather than Japan was the main concern of the US and had it not (mercifully) been for Hitler's idiocy to declare war on the US without any obligation to do so, the attack on Pearl Harbor would not have been a casus belli against Germany.
Of course the attack on Pearl Harbor provoked a readiness for war which had not occurred in US history since Fort Alamo (when the US were not officially involved) and had not been heard again until 9/11. But in spite of the tendency of western hemisphere isolationism that dominated US foreign policy until WW2 the US were not in need to pay such high a price to get the country into war after all. The attack on Pearl Harbor had in one respect been unprecedented in history. There had always been surprise attacks in military history, but none that involved the attacker secretly sneaking a significant distance round the globe before delivering their blow. While the unlikelihood of a success of such a surprise attack may have fueled the arguments for those claiming that FDR knew it also explains why the many warnings were so easily discarded. It was just considered to be unlikely or even impossible to sneak undetected for so large a distance.
With regard to the radar warning of the attack it is also important to keep in mind that apart from the misinterpretation of the Japanese attackers as the B17s expected from California there was not too much faith in the radar technology at that time as (in spite of its success during the Battle of Britain) it had been introduced to the US military rather recently.
As for the submarine sunk near the entrance of Pear Harbor, it should be noted that even more than 20 years later US ships fired according to president LBJ on fish (which still made a good casus belli against Vietnam in 1964). Reports of a submarine being sung in peacetime at so unlikely a place would have been prone to be considered likely to be similar "fish shootings" rather than a sign for a surprise attack unprecedented in human history.
Moreover, the whole battleship fleet in Pearl Harbor would have been quite a big sacrifice to be made deliberately. We often tend to fail to realize that the rethinking of aircraft carriers rather than battleships as the main naval force had not yet happened (or at the very least not yet been accepted by most) prior to the attack on Pearl Harbor. Of course the British had demonstrated at
Mers-el-KÈbir and
Taranto what aircraft carriers were capable of, but only after Pearl Harbor and the following carriers only battles in the Coral Sea and Midway it became widely realized that carriers were now the way to go. America's largest (and last) ever battle-ships, the Iowa class were all completed after the attack on Pearl Harbor (rather than being turned into carriers instead) and the last one of them to be completed, the USS Wisconsin was laid down even after Pearl Harbor (and also the sinking of the British battle ships Prince of Wales and Repulse three days later) which goes to show that the claims that FDR realized battleships would not be of primary importance in a war to come and could hence be sacrificed are not very credible. Also, the US were (cynical as this may sound) "lucky" at Pearl Harbor and I'm talking of chances here which (unlike the absence of carriers in the harbor) could not have been influenced by FDR. If the Japanese had launched a third attack wave (most pilots insisted on another attack to be launched but were overruled by admiral Nagumo) to destroy the repairing docks and the fuel tanks in Pearl Harbor the US fleet in the Pacific would have been paralyzed much worse than it was. It would have been way too much of a prize to pay for a casus belli (the war against Spain of 1898 goes to show that it is much cheaper than Pearl Harbor was to give a sufficient cause for war). Another such stroke of "good luck" in disaster was that no ship was sunk in the narrow inlet of the harbor (though the USS Nevada almost was) in which case the fleet would have been locked up for quite a while.
But let us for the sake of the argument assume for a moment that FDR was so foresighted as to anticipate the importance of carriers and the unimportance of battleships in the war to come and that he did know about the Japanese approaching. Would he not have ordered an attack from US carriers (which in this case he would have posted close enough to launch such an attack but far enough from Pearl Harbor to be out of harms way)? An attack on the Japanese carriers at the return of their first attack wave would have been an absolute disaster for the Japanese. Imagine their carriers Akagi, Kaga, Soryu, Hiryu, Shokaku, and Zuikaku to be sunk right there on December 7th 1941. I guess it is safe to say that that Pacific war would have become a much shorter affair, that FDR would have been intelligent enough to see this, and that this would have been the likely procedure if indeed FDR would have known about the impending attack and was ready to accept a strike at Pearl Harbor in order to have a casus belli against Japan.
With all this in mind I think that even though I have not read the actual books about the theories that FDR knew, I guess I have good reasons to be very skeptical about those theories. Moreover, how many people would have known if the US had been aware of such an attack? It would have hardly been the president and one trusted adviser only. The intelligence offices, the president, advisers on strategy etc. would have all known about it. How likely is it that every single individual in such a group of people knowing that thousands are about to die and that they could prevent it to keep mum before and after the attack? Not very likely I would say. There are the same theories about 9/11 and alleged awareness of the US government. Everyone knows my opinion of G. W. Bush and his advisers, but for the same reasons as given above I do not believe they knew (though one can argue that with some of the information they had been given in the months before they ought to have anticipated something and reacted accordingly). Such conspiracy theories are very interesting to read, but they rarely stand a careful check.
Once again an interesting historical topic from you F-22. Thanks for these threads
