A sizeable literature has been devoted to determining the effectiveness of United Nations (UN) peacekeeping in ending civil wars. Much less work has attempted to improve our understanding of the force-level commitments made by the UN to ongoing conflicts. We systematically address the issue of UN force commitments to civil conflicts and their relation to conflict hostility. Specifically, we posit that UN force deployments are a product of UN Security Council (UNSC) bias in favor of or against individual conflict factions and the battlefield performance of those combatants. To test our arguments, we employ newly collected data on UNSC resolution bias, monthly peacekeeping personnel commitments, and dynamic monthly-conflict conditions for African civil conflicts over the 1991–2008 period. We find that bias in UNSC resolutions is an important determinant of UN troop-deployment levels when its preferred side is sustaining higher casualties. These findings have important implications for peacekeeping effectiveness.