Barry, I didn't get to the end yet, but according to John Dewey's, President Roosevelt and the Coming of the War, 1941, the U.S. was privy to the attack 24 hours before it occurred but they decided to warn them by a much slower process than they could have because, as you wrote, Roosevelt wanted to get us in the war to fight Hitler. Churchill had been told Roosevelt in secret meetings aboard some naval ships that if the U.S. didn't get into the war, then England would likely be conquered by the Germans who had overrun France.