Even in long-running civil conflicts, governments may permit rebels to recruit and gather resources freely during years-long truce periods. Scholars and policy makers assume that these periods of forbearance allow rebel organizations to gather strength unchecked. Instead, with innovative evidence from five conflict zones in Northeast India, I show how leniency can actually undermine rebel organizations in the long run. Despite rebel leaders' best efforts, safety and comfort attract selfish opportunists who may later desert in battle, defect to the enemy, or abuse civilians. First, I show experimentally that the benefits of leniency disproportionately attract low-commitment recruits. By sampling in local recruitment hot spots, I gathered nearly 400 likely rebel recruits, testing their motivations with attitudinal questions and a conjoint survey experiment. Second, I conducted dozens of qualitative interviews with rebel leaders, rebel soldiers, and civilian observers, tracking how truce periods altered rebel recruitment and behavioral patterns over time.Verification Materials: The materials required to verify the computational reproducibility of the results, procedures, and analyses in this article are available on the American Journal of Political Science Dataverse within the Harvard Dataverse Network, at: https://doi.org/10.7910/DVN/CL0RU2. R ebellion is a dangerous business, but some times are more dangerous than others. During a government crackdown, rebel soldiers may risk life and limb and live in squalor and discomfort. In many long-running civil conflicts, however, rebel groups may be largely left alone by government forces for extended periods. In the most extreme cases, governments may permit rebel groups-either explicitly or tacitly-to recruit new soldiers, gather resources, and prepare for coming battles, as long as they do not attack government forces. Truce periods like this are surprisingly common and can be quite durable; in more than two dozen civil conflicts (generally separatist conflicts), rebels and government forces have transitioned from active conflict to periods of toleration lasting years (Table 1). Even if neither side has any intention of negotiating disarmament or formal autonomy, warring parties may face substantial pressure from international observers or domestic constituencies to halt the bloodshed. As a result, rebels and government forces may agree to an indefinite cease-fire that freezes hostilities but leaves both sides armed and core issues unresolved. The terms may vary substantially, but they reflect the same basic trade-off: Rebels are allowed to gather recruits and resources largely unchecked so long as they do not fight the government. These deals are neither bridges to a permanent settlement nor attempts to "divide and conquer" rebels; they are generally offered to all rebel factions at once and rarely lead to later disarmament.How do rebel organizations change when the government permits them to operate in relative safety? It seems logical that toleration should monotoni...