A Staff Report from the Straight Dope Science Advisory Board

Did Roosevelt know in advance about the attack on Pearl Harbor yet say nothing?

February 28, 2001

Dear Straight Dope:

I have just heard the disturbing rumor for the umpteenth time that Roosevelt knew that Pearl Harbor was about to be bombed, and said nothing, because he wanted America to be drawn into the war. Is this the truth?

One is tempted at this point to decry the legacy of Richard M. Nixon, whose actions as President (and, some allege, as a presidential candidate) made generations of Americans unwilling to put any trust whatever in their leaders. In this view, Nixon helped besmirch the character of one of the most capable and beloved Presidents by making it possible to believe that Roosevelt would allow thousands of Americans be killed or wounded in order to further his own political goals.

That temptation evaporates when one discovers that such rumors started almost immediately after the bombing itself. In fact, Thomas Dewey (Republican candidate for President in 1944) tried to turn it into a campaign issue; he and several Republican senators claimed that "certain Japanese codes before Pearl Harbor" had been cracked, and that FDR "knew what was happening before Pearl Harbor, and instead of being re-elected he ought to be impeached." In the end, Dewey dropped the issue; partially because Army Chief of Staff General George Marshall provided evidence to the contrary, and partially because Dewey knew if he were to make such accusations in public, the Japanese government would realize that their codes had been compromised, which would prompt them to change their codes and cause serious hardship to future American operations.

On the face of it, there's a ring of truth to the rumor. The American military had broken some Japanese codes, and had received prior warning of an attack, both from notes they intercepted as well as notes the British cracked and passed on. Given that Marshall warned Pacific army commanders "the United States desires that Japan commits the first overt act," how hard is it to believe that Roosevelt allowed the surprise attack to occur in order to bring a vocally isolationist Congress and public into supporting war with Japan?

But let's look at each of these allegations in detail--you may note some flaws.

The American military had broken Japanese codes.

Yes. However, what they had broken were diplomatic codes. During the pre-war negotiations with Japan, Roosevelt often knew what the Japanese were prepared to offer and willing to settle for. The messages sent on December 6th made it perfectly clear to Roosevelt that the Japanese government was planning to declare war upon the United States.

So the American government knew an attack on Pearl Harbor was coming.

No. The Japanese government was not in the habit of informing its diplomats of planned military strikes in detail. So while the Americans knew that Japanese diplomats had been instructed to deliver a certain message to the U.S. government at 1 p.m. on December 7 and then destroy their cipher machine and secret documents, and from this deduced that something big was about to happen, they did not know where to expect the initial attack. The Pacific Ocean's a big place, and there were lots of targets available to the Japanese--the Philippines, Dutch East Indies, Singapore, etc. Admiral Stark recognized that the Japanese were planning to attack somewhere, but told his subordinates it would be "against either the Philippines, Thai, or Kra Peninsula or possibly Borneo." As is well known, the American military failed to take advantage of what little warning it did have through bad luck and incompetence.

But the carriers were out to sea on maneuvers, leaving behind several outdated battleships. So the Pearl Harbor attack wasn't nearly as successful as it could have been. Doesn't that mean that someone had ordered them to take precautions by sending out the carriers?

Try telling Roosevelt's staff and the navy that the Pearl Harbor attack wasn't nearly as successful as it could have been. Most of them believed that the Pearl Harbor attack had completely obliterated American strength in the Pacific.

As for the carriers, it would be another six months before their importance would be proven beyond a doubt, at the battle of Midway. At the time Pearl Harbor was attacked, nearly all naval leaders--including the Japanese--considered carriers and their aircraft best suited to reconnaissance. The real fighting would be left to the battleships, many of which were sunk or badly damaged after Pearl Harbor.

While the Americans knew some attack was coming, they did not know what type of attack. Had the air raid been followed up with an invasion, Pearl Harbor could not have held out for long, and the United States would have been without one of its major bases in the Pacific, in addition to having lost the fleet.

Even so, without the Japanese attack, America would never have declared war upon Japan.

Not true. Most people point to the August 1941 resolution to keep draftees on duty for more than twelve months, a measure that passed by the narrowest of margins, 203-202. But antiwar sentiment was waning quickly, especially in the wake of German U-boat attacks upon American vessels. In September, a poll showed 67 percent of the American public felt the United States should risk war rather than allow Japan to grow more powerful; 70 percent felt the United States should risk war with Germany. Many in Roosevelt's cabinet and the press felt that the President would have no difficulty in getting a declaration of war against Japan following the breakdown in peace negotiations in late November. But it was Roosevelt who refused to push the issue, instead waiting for Japan to make the first move.

In order to believe that Roosevelt knew about the coming Pearl Harbor attack but kept mum, you have to believe he had better information than any of his subordinates in the government or the military--information that since has been destroyed, since no one has been able to find it. Moreover, you have to believe that Roosevelt was willing to sacrifice most of the Pacific fleet, and possibly one of the most important American naval bases in the Pacific, probably crippling American operations against Japan for the next two years (by which time the Japanese would likely have taken over the Pacific and begun operations against the American West Coast) in order to gain public support for a measure the public already supported by a two-to-one margin. You also have to believe that Roosevelt--who had been Assistant Secretary of the Navy, who always claimed that if he hadn't gotten into politics he would have liked to have been an admiral, whose first campaign song for President was "Anchors Aweigh" (before being replaced by the more appropriate and upbeat "Happy Days Are Here Again")--would countenance the deaths of thousands of U.S. sailors for a few extra votes in Congress--again, for a measure that many observers felt would pass easily.

If you're willing to believe that, I've got some great information on the Vince Foster murder I'm willing to sell you.

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