UC Merced

Abstract: Any act of battlefield violence results from a combination of organizational strategy and a combatant's personal motives. To measure the relative contribution of each, our research design leverages the predictable effect of ambient temperature on human aggression. Using fine-grained data collected by US forces during the Afghanistan and Iraq conflicts, we test whether temperature and violence are linked for attacks that can be initiated by individual combatants, but not for those requiring organizational coordination. To distinguish alternative explanations involving temperature effects on target movements, we examine situations where targets are stationary. We find that when individual combatants have discretion over the initiation of violence, ambient temperature does shape battlefield outcomes. There is no such effect when organizational coordination is necessary. We also find that ambient temperature affects combat-age males’ endorsement of insurgent violence in a survey taken during the conflict in Iraq. Our findings caution against attributing strategic causes to violence and encourage research into how strategic and individual-level motivations interact in conflict.