Abstract. Violence against civilians in civil war is widely thought of as a strategic choice by combatant groups. We argue that a common strategic logic of competition underlies diverse theories of civilian victimization. We develop a theory of strategic complements in victimization, hypothesizing that an armed group’s propensity to victimize civilians will increase with its expectation that its competitors will act likewise. We test this argument by structurally estimating a formal model of strategic interdependence between armed groups using data from the Colombian civil war. Our findings indicate that strategic expectations are responsible for a substantial amount of violence against civilians: the two major combatant groups would have systematically victimized civilians in 12–15% fewer municipalities if they had expected no violence by their rival. Examining causal mechanisms, we also find that victimization in the Colombian case was more likely aimed at controlling civilians than at influencing peace negotiations.