This article examines the relationship between mass resettlement and political conflict. The author theorizes that states can use mass resettlement to extend control over contested frontiers. Settlers whose land rights are politically contested will disproportionately participate in violence to defend the incumbent regime. The theory is tested using data on resettlement and violence in postcolonial Rwanda. The author shows that the Hutu revolutionary regime resettled some 450,000 Hutus after independence to frontier and Tutsi-dominated areas to defend itself against external Tutsi militias. The author contends that the invasion of the Tutsi-led Rwandan Patriotic Front (RPF) in the 1990s threatened the Hutu settler population because the RPF sought the repatriation of Tutsis onto redistributed land and that consequent land insecurity incentivized violence against Tutsis in 1994. The article identifies the positive effect of resettlement on locality violence during the genocide via a geographic regression discontinuity design. A process tracing of one notoriously violent resettled commune supports the theorized causal sequence. In light of these findings, the author suggests that research should refocus on the way that conflict shapes ethnic demography and that, to understand participation in state-sponsored violence, scholars should attend to the threat posed by regime change to individual livelihoods.