Su, MingyangThis thesis addresses puzzles related to violence against civilians in civil wars. Specifically, the thesis emphasizes civilians’ roles in influencing rebel groups’ decisions to escalate indiscriminate violence against civilians in conflicts. Previous literature on violence against civilians suggest that rebel groups in civil wars may kill selectively or indiscriminately. These studies argue that indiscriminate violence is counter-productive since it eliminates incentives for civilian collaboration with the perpetrator. Yet, indiscriminate violence remains a common phenomenon. Why do rebels use indiscriminate violence when doing so is counterproductive? What explains the occurrence and intensity of indiscriminate violence? The thesis answers the puzzle by focusing on civilian mobilizations against rebel groups. It argues that civilians’ resolve to mobilize against rebel groups is important in influencing rebels’ decisions to escalate indiscriminate violence. Civilians can signal this resolve by engaging in violent and nonviolent risky mobilization against rebels. Statistical tests, which are based on conflict event data collected from civil wars in Africa, reveal that the occurrence, long duration, and high frequency of civilian mobilization negatively correlate with violence. The thesis further traces a detailed single case study on Boko Haram and four cross comparison cases to provide qualitative evidence on the mechanisms of the theory. The thesis makes two theoretical contributions to the field of conflict. First, when explaining indiscriminate violence, the thesis shifts the attention to civilians’ decisions and resolve to reduce violence. Second, the theory provides novel mechanisms on how civilians mobilize to deter rebel groups from using indiscriminate violence. The mechanisms also link specific predictions on the conditions under which civilians are likely to be successful in deterring rebels from using violence.enDissertationInternational relations