system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What was Japan thinking when it attacked Pearl Harbor? Did they actually believe they could beat the U.S. in a war?
gpt
The Japanese leadership most definitely didn't think they could win the war decisively. A member of the leadership even said something along the lines of "fighting the US would be like fighting the whole world" (the US alone had a larger GDP than the entire axis). 

The thing is, the war had very much already preordained by the time pearl harbor happened. The oil embargo, aid to China, lend lease, etc. War with the US was already inevitable. Pearl Harbor was an attempt to seriously hamper the US navy and, in the end, fight long enough to win a truce that would allow Japan to keep at least some of its gains.