Although some rebel groups work hard to foster collaborative ties with civilians, others engage in egregious abuses and war crimes. We argue that foreign state funding for rebel organizations greatly reduces incentives to "win the hearts and minds" of civilians because it diminishes the need to collect resources from the population. However, unlike other lucrative resources, foreign funding of rebel groups must be understood in principal-agent terms. Some external principals-namely, democracies and states with strong human rights lobbies-are more concerned with atrocities in the conflict zone than others. Multiple state principals also lead to abuse because no single state can effectively restrain the organization. We test these conjectures with new data on foreign support for rebel groups and data on one-sided violence against civilians. Most notably, we find strong evidence that principal characteristics help influence agent actions.Wartime atrocities are often portrayed as irrational, depraved, and senseless. However, recent research in this area has increasingly viewed violence as strategic, adopting Arendt's argument that violence is rational to the extent it assists actors in attaining their goals. 2 Scholars have suggested that actors resort to victimizing civilians to improve their bargaining position over their adversary's, expedite war termination, and generate resources. 3 This vein of research also claims that attacks on civilians are intended to alter the behavior of the targeted groups 4 and to eliminate disloyal or threatening populations. 5 We focus on the manner in which rebel groups obtain resources and how this influences their behavior toward civilians. All rebel organizations, regardless of their ideology and putative grievances, need to secure resources to finance their operations. 6 Guns, uniforms, and other war supplies are expensive to procure. However, as Weinstein has shown, rebel organizations differ greatly with respect to the resource environments in which they operate, and this often shapes their behavior toward civilian populations. 7 Resource-poor rebels without easy access to commodities such as drugs and gemstones must rely on the goodwill of the population. By fostering deep local ties and protecting the interests of ordinary people, rebel organizations can both secure goods and ensure "moral commitments and emotional engagements" to their cause. 8 By contrast, resource-rich rebels are less dependent on civilians for their needs and their survival-a condition that may lead to abuse and mistreatment of civilians.