What's common knowledge about WWII in Japan?

Watched a movie last night called "Emporer" (starring Tommy Lee Jones, Matthew Fox etc). It wasn't a bad movie, it is about finding Japanese war criminals and if the Emporer was involved. One line made me giggle "we need to find who started the war". Uh yea you are in the wrong country.

 

I'm following the "someone forgot their hanko that day" theory. I think Martin proposed that one in another thread.