Does military intervention affect civilian death tolls? Existing research has focused on international actors’ ability to limit ongoing slaughter but has not examined their ability to prevent the emergence or escalation of such killing. I develop a theory of government killing that accounts not only for the government’s decision to kill civilians but also for the transference of the killing order from leader to perpetrator, and for the perpetrator’s implementation of that order. Focusing on the principal–agent relationship produces new expectations about the effects of military intervention on government killing. I find that international actors are well equipped to limit civilian slaughter: intervention supporting the government decreases the likelihood that a government orders civilians killed. Intervention against the government leads to a decrease in death tolls when killing occurs. Ultimately, supportive intervention is a useful means of preventing government killing, while oppositional intervention limits its escalation once it begins.