something very much related to this topic is that the modern concept of the Westphalian State was a direct result of the Thirty Years War which was one of the most brutal wars ever waged on European soil (Wikipedia article for one of the worst massacres of the war just to give you a taste. the city of Magdeburg was almost entirely depopulated.). when we learned about it in school it really struck me that the "reasons" we're given for wars are almost always bullshit and put in place to coerce the populace to fight for the interests of their rulers.