In a civil conflict, how does one actor’s choice to victimize civilians affect the chance that other actors do the same? In this paper, we first derive implications about the strategic interdependence of victimization choices from the most prominent existing theories of violence against civilians in civil war. We show that these theories lead to distinct conclusions about whether one group’s choice to victimize civilians has a positive, negative, or zero effect on whether other groups do so. This suggests that empirical evidence about strategic interdependence can be used to discern among these competing bodies of theory. To uncover such evidence, we analyze municipality-level data from the civil conflict in Colombia. We structurally estimate a formal model of the strategic interaction between the conflict actors: the left-wing guerrilla groups (FARC and ELN) as well as the right-wing paramilitaries. We find that there are strategic complementarities, which is consistent with theories of victimization as a means of forcing civilian cooperation or of signaling a group’s strength.