Here's the thing. 1. War is a topic, not a problem. 2. Nothing is a problem until you make it a problem. And 3. Dramatica is best used when looked at as describing the SOURCE of the problem, NOT the problem itself.
So as a topic, 'war' is not a problem. You can make it a problem by having it be the result of a problematic Activity, Situation, Psychology, or Mind. You've been given that advice above. But the thing is, war as a topic can also be made the source of the problem rather than what we've made to be the problem. Look at @LunarDynasty's example. Did the war lead to famine, or did the famine lead to war?
My point is that when you are trying to determine which throughline something falls in, it's important to know whether you are asking about the problem or the source of the problem. The difference is that stories that show how war leads to what those characters see as a problem probably fall under one of the external quads (assuming war is referring to multiple parties engaged in combat and not somehow referring to some kind of internal war). But stories that show how something leads to the war that the characters see as a problem can fall into any quad. Without knowing what that something that leads to war is, there's not enough information to know.