How do networks shape civil conflict? In this dissertation, I explore this question through new concepts, new data, and new techniques. First, I examine the effects of networks that link members of different identity groups during genocide, authoritarian repression, and civil war. Drawing on 160 qualitative interviews, census data, and a nationwide survey in Bosnia & Herzegovina—the first nationwide survey on rescuers during conflict—I show how cross-group social capital led people to assist outgroup contacts during the 1992-1995 war in Bosnia. Second, I turn to the role of road networks in connecting antagonistic populations and armed groups. Combining weather data, conflict event data, and historical road maps of Africa, I examine how disruptions in a country’s road network due to heavy rainfall affect levels of violence. Third, I develop new techniques for causal inference in weighted networks and show how they can be used to measure interventions that either spread conflict or reduce it. Together, these projects—one observational, one quasi-experimental, and one methodological—seek to guide academics in measuring the role of networks in civil conflict in order to help policymakers prevent future bloodshed.