I've tried to do some Google sleuthing on the subject but I'm afraid I may have to search for specific wars rather than the general term.
I'm wondering if anyone knows of any sources that look at the philosophy of war, common tropes of why wars being, the "powder kegs" of history, or similar? I'm not concerned with religious war because those reasons are pretty obvious. I'm looking for like some in-depth studies on why medieval or ancient societies would have wages wars with neighbors that go beyond "well, Side A had x-resource so Side B decided 'hey, we want that!' and went to war."
Maybe the War of the Roses is a good candidate for possibly getting a good idea for how relations sour and escalation with certain events cause a string of events to unfold? It seems that a wide variety of events happened that kept the war up for 4 decades. I'm looking for like an analysis of the escalation; not necessarily for this war, but how escalations lead to one side declaring war on another. Maybe what I'm looking for are specific wars that had complex reasons for beginning? I know feudal Japan and China had some conflicts like this.
Maybe I'm shooting for the moon and this doesn't exist...
This question is too wide for a good answer but i´ll try my best. For a start i would recommend the book The dictator´s handbook (2011) to understand the basics of power. In summary power is the distribution of wealth. Every war has a casus belli, but usually the reasons are power and economy, even the religious wars. If you think religious wars are about ideology, check out Martin Jan Mansson map with the comerce routes in the 11th-12th century and you will see that the middle east comerce was far more developed than western europe. If you want to study about war and causes of war, i would recommend you to learn about the hundred years war, politics, family economy and society unite, and i think is the best test ground for learning about war. If you want something more recent, maybe Henry Kissingers diplomacy can be a good start read for war and diplomacy in the 20th century, with the obvious pro-american bias.