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. So at the end of World War I, let's see how you guys are with vocabulary here. There's a treaty that ends the war. It's called the Treaty of Versailles.