What did Roosevelt think he was accomplishing by waiting to let the Japanese attack Pearl Harbor?

Answer 1

He needed a reason to get the Americans involved with the war.

AnswerIt will long be debated if Roosevelt knew of Pearl Harbour and let it happen. He had the intelligenc reports, knew the Japanese Plan for future conquest, and the carriers just happened to be out while the rest of the fleet was sleeping on Sunday morning. He had been secretly supplying the allies with planes, ships, and other war materials, for awhile. He also knew the American People wanted no part of war and they felt it was none of our business. Pearl Harbor united the American People and mobilized America for war far better than he ever could.

There is also no evidence that Roosevelt (or any other ranking American) knew of a specific plan to attack Pearl Harbor, let alone even an approximate date that it would happen. American planners had long recognized that Pearl Harbor would be a logical attack point for the Japanese, but had discounted the effectiveness of such an attack. In particular, it was thought that aerial torpedoes could not be used in the shallow waters of Pearl, and that aerial bombing would prove only modestly effective, not enough to seriously threaten the Pacific Fleet.

The modern historical perspective is that Roosevelt and senior advisers recognized the possibility of an attack on Pearl Harbor and did nothing to specifically discourage the Japanese from such a plan; however, this can be said about a large number of other potential targets that the Japanese might have attacked also. The absence of the U.S. carriers was simply bad luck for the Japanese - they had left port several days before on scheduled errands. In order to schedule that the carriers would be missing on purpose, Roosevelt would have had to know of the exact date of the attack a month or so in advance, and there is not a shred of archival evidence to support such a conspiracy theory.