Existing research suggests that rebel groups with aspirations for international legitimacy avoid practices that harm their reputation. This study asserts that this logic does not necessarily apply to forced recruitment of fighters. Unlike other coercive practices, recruitment is not a mere tactical choice but a foundational requirement for organizational survival. The indispensable need for fighters compels rebels to weigh recruitment needs against aspirations for legitimacy and balance the imperative for survival against the potential for international backlash. I argue that pre-war social origins condition the recruitment practices of legitimacy-aspiring rebels by boosting both voluntary and materially-motivated recruitment. Pre-war ties to civilian-led organizations provide groups with networks for disseminating ideological appeals, fostering trust, and cultivating collective convictions favoring violent mobilization, thereby enhancing the ability to attract voluntary recruits. The boost in voluntary recruitment demonstrate rebels’ organizational capacity and serve as humanitarian justifications for external supporters. External support, which can be used for monetary incentives, attracts recruits motivated by tangible benefits, further reducing the need for forced recruitment. Thus, rebel organizations best positioned to refrain from forced recruitment are those with both aspirations for international legitimacy and pre-war ties to civilian-led organizations. Using cross-national data on 115 rebel organizations, I find strong empirical support for this hypothesis. My work builds on the growing body of research on rebels’ engagement with international audiences, highlights the role of social origins in shaping future behavior, and suggests that the constraints they face in galvanizing domestic support limit legitimacy-aspiring rebel groups’ adherence to international humanitarian laws.