Bases, Bullets, and Ballots: The Effect of U.S. Military Aid on Political Conflict in Colombia

Does foreign military assistance strengthen or further weaken fragile states facing internal confict? We address this question by estimating how U.S. military aid affects violence and electoral participation in Colombia. We exploit the allocation of U.S. military aid to Colombian military bases, and compare how aid affects municipalities with and without bases. Using detailed political violence data, we find that U.S. military aid leads to differential increases in attacks by paramilitaries (who collude with the military), but has no effect on guerilla attacks. Aid increases also result in more paramilitary (but not guerrilla) homicides during election years. Moreover, when military aid rises, voter turnout falls more in base municipalities, especially those that are politically contested. Our results are robust to an instrument based on worldwide increases in U.S. military aid (excluding Latin America). The findings suggest that foreign military assistance may strengthen armed non-state actors, undermining domestic political institutions.