Why was FDR happy? He believed the Nazis had to be defeated to save democratic Western Civilization. Until the invasion of Russia in Spring 1941, Britain had been holding on alone, barely. In 1941, the Germans were rolling across Russia and it would not be for another year that we would learn Russia would survive the attack. A Japanese attack on the US would finally create a consensus that the US had to enter the war and allow us to give the British full support.
Roosevelt did not need to trick the Japanese into attacking us. They had already taken the decision to seize SE Asia, which meant attacking the Philippines and the US Asiatic Fleet, Far East Air Force, and Army ground units. They had already decided on war against the US.
Thanks, Tanker, but I think we are not talking of the same points. I am not saying we shouldn’t have gone to war. I am not saying the Germans and the Nazis didn’t need to be stopped and I am certainly not saying FDR ‘tricked’ the Japanese into attacking us. My point is that circumstantial evidence shows that FDR knew Pearl was going to be hit and he knew when and to what extent, and that he let it happen and augmented the effect by delaying the Japanese diplomat’s presentation of the war declaration. While this did get us riled up like hornets, with Americans RUNNING to the enlistment offices, it killed thousands of sailors at Pearl Harbor that could have at least defended themselves with the advance warning that was withheld.
A) Recall event of 22June1941.
B) Japan needed oil, and after a world-wide embargo became effective (thank you FDR and Churchill at Placentia Bay).
C) Japan always "gamed" their moves. The gaming of their move south (say NEI and oil), Pearl Harbor as a threat to their flank is seen. Hart and his "Asiatic Fleet" was not seen as a major force - largest warship is CA.
D) Japan knows, via the captured Blue Funnel streamer, from the COS papers that Britain is in no position to sustain a naval offensive in the Far East. (See Chapman's The Price of Admirality). The only worry - the Pacific Fleet, now lessened because FDR move major elements to Altantic - that convoying thing. Puzzle - how many fleet oilers remain at Pearl Harbor?
E) The US via FDR, committed to the armed support of British and Dutch terrority - unconstitutionally and not revealed until the Pearl Harbor Hearings
F) There was no treaty to defend Britain or the Dutch - nothing ratified by the US Senate.
G) Consider international law as well as the US being a declared neutral country at the time. And what that meant.
... And so on.
Timing is everything.