Answer:
America and resources
Step-by-step explanation:
The reason is America and resources. Japan is an island nation with minimal resources such as oil. So, they have to conquer other nations to get the resources. China was relatively weak back then so they took Manchuria. They also wanted the Dutch West Indies (Now Indonesia) which was plentiful in oil. To do that, they would have to invade the the colony which was owned by the Netherlands, dragging Japan into war.
America, seeing Japan so expansive and getting more and more powerful, set tariffs and sanctions on it, which did not help at all, as a lot of their oil came from America.
That's what made Japan different, they were kind of forced to invade different colonies and nations (but that still does notmake it right to kill and massacre people like they did.).