Last WW2 question :)?

Yes, you certainly could say that, although as it worked out, FDR didn't have to do much calculating.

Japan was making a move to become the dominant economic player in Asia, and had already invaded vast areas of China. But it was getting 80% of its oil from the US, until Washington turned off the tap. From that point, both sides could see that war was all but inevitable. The Japanese turned their attention to the vast oil fields of the Dutch East Indies, but knew that launching an invasion would almost certainly get a military response from the US. Finally, they reached the conclusion that the best option was to neutralise America's main weapon, the Pacific Fleet, in one fell swoop, thereby discouraging the US from getting involved in a war so far away, and leaving the Japanese more or less free to pursue their goals. With no real weapons left in the Pacific, the Americans would do the pragmatic thing and not interfere with Japanese goals in the region. Or so went the reasoning.

Japan could never have predicted that delivery of its declaration of war would be delayed until after the attack, something that played a huge role both in American public opinion, and in the American military response. An embarrassing defeat AFTER a declaration of war might have brought serious reflection on what to do next, but a "sneak attack" galvanized the whole country and made the military response inevitable.

There have been some fairly silly things written about FDR "knowing" about the Pearl Harbor attack in advance, but certainly he knew, with the breakdown in talks that week, that a Japanese attack -- somewhere -- was very likely. And, yes, in many ways, it solved a problem for him. He could see that sooner or later, the US would have to deal with the sheer evil of Hitler's Germany, but Americans were overwhelmingly against getting involved in "foreign wars". (Charles Lindbergh, for example, the absolute epitome of a beloved American hero, was crossing the country speaking to huge crowds about what a swell guy Hitler was.)

The attack on Pearl turned around American public opinion overnight, and a couple of days later, Hitler was kind enough to declare war on the US, something that staved off any troublesome discussion of whether the US should just focus on Japan.

What film did you watch? Japan attacked the U.S. fleet at Pearl Harbor because the U.S. stopped sending oil to Japan. Read the rest of the explanation in this link written by someone who recalls the events at the time. I agree that the U.S. knew of a pending strike.

I don't know the film you watched but I will recommend two books "Day of Infamy by John Toland and At dawn we Slept by Gordon Prange. Toland speculated that there was knowledge of Pearl HArbor beforehand and that Adm. Kimmel and Gen. SHort were basically thrown under the bus as it were. Prange, one of the preeminent historians focusing on Pearl Harbor, disputed this in several books. The attack was a calculated attack by Japan and I doubt (Much as I like and respect Toland's work) there was a conspiracy to get us into war by ignoring intelligence. Eithere way, read both books.

the u.s never expected the attack of pearl harbor they new that there were going to probley join the war sooner or later but they never thought japan would bomb pearl harbor . the reason why japan bomb pearl harbor was because u.s.a was loaning money and selling army equment to the allies .

Send me the notes you wrote down and a copy of the film you talk about and I'll answer. Cheers.