Is It Possible to Classify World War II?

The Second World War will be studied by historians as long as human civilization endures, since the scope and scale of the conflict puts it in a class by itself, but what kind of war was it? What kind of war was the Second World War? It is a deceptively simple question, since it implies that there is some kind of taxonomy of warfare, and that the Second World War neatly fits into some taxon. Thus the question implicitly appeals to theories of war that remain unstated in the question. One could relativize the inquiry with some formulation like, “According to a Marxist perspective, what kind of war was the Second World War?” This would at least make our theoretical framework explicit, and would narrow the inquiry to a manageable scope. I’m going to tackle the subject in an open-ended way, without doing this.