[jaguar]

to echo what griff stated, the key turning point was oil, an oil embargo was a huge provocation agains't the japanese and virtually forced their hand. Point safely proven.

The second point is that the administration wanted to enter the war(a german owned Eurpoe wasen't a too preasent reality), but public opinion was agains't such action, by provoking Japan into war, it opned the route to supporting the European war too.

Mabye on top of some high collage reading, you could have alook on the theory behind how a nations national interest and therefore, its foreign policly is formed.