Abstract: What role does transportation infrastructure have in shaping the trajectory of violence in civil wars? While an extensive literature has examined how transportation infrastructure such as roads and railway influence political and economic development and the propensity for conflict initiation, less work has considered how such infrastructure molds the way ongoing wars are actually fought. We argue that roads influence the behavior of insurgents in civil wars by bestowing strategic value on cities and towns with higher levels of road infrastructure. Attacking these locations imposes high costs on the state, while also presenting insurgents with opportunities to engage in road-based looting. We find support for our argument using a rich variety of data and empirical strategies from a period of intense fighting in the Colombian civil war (1988-2005), which includes conflict event data, an instrumental variables strategy, and a survey of inter-city trade. The results suggest transportation infrastructure molds insurgent tactics and raises caution about the potential of such infrastructure projects to reduce conflict occurrence.