The idea that war is unprofitable and best avoided if possible was already a big theme in Sun Tzu's Art of War. War is insanely expensive, both in terms of the

The idea that war is unprofitable and best avoided if possible was already a big theme in Sun Tzu's Art of War. War is insanely expensive, both in terms of the people, resources and infrastructure lost, and in terms of the opportunity cost of what you could have done instead. Sure, in principle putting in some fixed amount of resources to get a piece of land forever is worth it eventually. But that's not how it usually works out. If you conquer land from somebody, they don't roll over and accept that. Chances are you will be back on the same battlefield, fighting over that same land a couple decades later. Or if it's large enough empires fighting each other you fight over a different piece of land in a couple years. But either way, the country that can maintain peace without too many concessions and focus on their economy tends to be better off. The only major exception is colonization, where you fight against people who don't have a cohesive country that could retaliate later on. The cost of war has arguably gone down a lot in the last two centuries or so, since we can now fight total war and have farmers ploughing the field at the same time, due to the insane efficiency gains in agriculture. At the same time the benefits of gaining land have gone down. Doubly so the benefits of gaining bombed-out land where the population was displaced by said war.