Some people would argue even in the early 30s you could consider some of that World War II because of the Holocaust beginning around that era. So let's take a look at it and see what we can learn, alright? Causes and effects of World War II. There's a lot of causes, there really are. Imperialism and nationalism, economic reasons. But we're going to try to give you one term to kind of hang your hat on so if you have to write about World War II you don't have to think too hard because you know what the cause was. I would argue that the cause of World War II is World War I.