I used to blame religion for mass warfare, and I'm sure that before the 20th century they were an effective tool for organized violence. But it seems that once we hit WW1, way more death was wrought by appeals to national identity, statehood, and complex interjurisdictional treaties.
Discussion
National identity was a huge vehicle for the push for brexit, not related to war I know. I'm not sure there are too many complicated inter-jurisdictional treaties nowadays. Statehood is the big one, we don't need to look too far outside of MSM to see that happening right now 🇺🇦