Civilian displacement is a regular, massive feature of civil war violence. This book provides a new way to think about displacement, by connecting it to how armed groups target violence against civilians, and how civilians respond. Individuals escape selective violence, civilians relocate together to avoid indiscriminate violence, and groups experience political cleansing following collective violence. Political cleansing is the expulsion of civilians from their communities based on a shared identity or trait. While it is difficult to detect civilians’ loyalties, the book shows that elections can both facilitate and incentivize displacement by revealing civilians’ political preferences; and giving elites a stake in the electoral composition of a community, motivating them to ally with armed groups. The book traces how democratic reforms triggered both processes in Colombia, leading to a major intensification of the war and to one of the highest populations of internally displaced people in the world. Combining evidence collected from remote archives, interviews with ex-combatants and displaced people, and quantitative data from the government’s displacement registry during nearly two years of fieldwork, the book connects Colombia’s political development and the course of its civil war to displacement.