Postulating grievance‐based mechanisms, several recent studies show that politically excluded ethnic groups are more likely to experience civil conflict. However, critics argue that endogeneity may undermine this finding since governments’ decisions to include or exclude could be motivated by the anticipation of conflict. We counter this threat to inference by articulating a causal pathway that explains ethnic groups’ access to power independently of conflict. Focusing on postcolonial states, we exploit differences in colonial empires’ strategies of rule to model which ethnic groups were represented in government at the time of independence. This identification strategy allows estimating the exogenous effect of inclusiveness on conflict. We find that previous studies have tended to understate the conflict‐dampening impact of political inclusion. This finding suggests that grievances have been prematurely dismissed from conventional explanations of conflict, and that policy makers should consider conflict resolution methods based on power sharing and group rights.