This is a pretty reductionist view of war. You can't reasonably deny the importance of economic factors, but attributing all of war to economics is a very opinionated view and I would argue pretty specific to a particular academic school of thought. I'm reminded of Stringer Bell in "The Wire," trying to use his business school lessons to evaluate every part of the drug trade. Avon stops him mid-sentence and says, "String, this ain't about your business class. This ain't that part of it. It's that other thing." Sometimes that's true of war, too.