Recent research on violence against civilians during wars has emphasized war- related factors over political ones. For example, factors such as control of territory or characteristics of the armed groups have been prioritized at the expense of factors such as ideological alignments or local political competition. In this paper, I argue that the emphasis on war-related factors is conditioned by the scope conditions of previous theories, which have focused on irregular civil wars. I switch the locus of attention to so- called conventional civil wars, and I introduce a theoretical framework that takes into account both political and war-related factors. Hypotheses are tested using data on 1,377 municipalities during the Spanish Civil War. I find that levels of prewar electoral competition explain variation in levels of direct violence from both the left and the right in the areas they controlled at the beginning of the war, but that war-related factors gain explanatory relevance after the onset of conflict, when control changes from one group to the other. In particular, there is a clear endogenous trend whereby subsequent levels of violence are highly correlated with initial levels of violence. I argue that the mechanism behind this is civilian collaboration with armed groups. In short, the paper demonstrates that an understanding of the determinants of violence requires a theory combining political cleavages and wartime dynamics.