What is/are a central theme(s) of World War II?

Answer 1

Power, Revenge, Idiocy, and Pseudo-gods.

Oddly enough, World War II was just a continuation of WW I. During the Treaty of Versailles, after WWI, Germany lost a great deal of land. Hitler was determaned to take revenge and retake what he thought was his own. On top of that, even though or possibly because of, he was practically a peasant growing up, once in power he began to believe he was the god of the perfect race. He had even went to jail in his youth, because of his beliefs which coinside with the Germany of that day. But with his charisma, he was able to gain followers which grew and grew and empowered him. He never lost his beliefs, but rather allowed them to possess him, as if he was the bride of a demonic illusion of his own desire. And thus it began.
As for Japan's decision to get caught up in it, I could not give you any exact details. But I am sure it would still fall under the power and pseudo-god syndrome. As you research this further, do not forget Fat Man. So much detail is given on Little Boy, Which of course was the bomb that destroyed Hiroshima, but Nagasaki only gets a few details given to her attack. It's still an extreamly important event, which deserves more time given to it.
Hope you get lots of good info on all of this tragic experience that stupid humans did to themselves, and to all humans, and to the animals, and Earth herself.

Answer 2

A central theme of the war was fighting against fasicst / Imperial regimes that sought to impose their own political will on other people.

Answer 3

It was an attempt to re-allocate natural resources.