In the context of a global security framework that mitigates interstate conflicts, nation-states establish a reputation for resolve by supporting foreign insurrections. Our theoretical predictions indicate that states with a greater number of co-ethnic groups abroad are more inclined to endorse foreign uprisings, resulting in higher political inclusion for such groups. With a dataset comprising over 280,000 ethnic group × sponsor state × target state × year observations, our analysis corroborates the role of reputation-building through co-ethnicity narratives as a determinant of sponsor state engagement. We argue that this mechanism engenders political concessions within target states, ultimately benefiting groups associated with reputed potential sponsors.