A lot of people on here are making the point that war is profitable in many cases. They aren’t wrong, but it’s much simpler than that and has nothing to do with money. The entirety of the sovereign state based system we live in is predicated on the premise that to consolidate power you have to have a monopoly on use of force. And when you have a bunch of individual states claiming sovereignty over a bunch of individual territories, the only way that sovereignty is actually worth anything is if that state is willing to put up a right to prove it. I think the only way we will ever get away from war in the way we see it now is by moving onto an Earth-encompassing single state. We are a long, long way off from that.