This article offers an explanation for the failures of US military assistance programs in some countries. The author argues that the effects of military aid are conditional upon the vulnerability of the recipient regime. Power consolidation by an insecure leader often provokes violent opposition. However, because military aid strengthens the security forces of the recipient state, it generates a moral hazard that encourages exclusionary power consolidation, with the expectation that continued military aid will help manage violent blowback. Using proxies for regime vulnerability and an instrument for US military aid, the study shows that military aid increases anti-regime violence in new regimes (particularly new democracies) and in all personalist regimes. In contrast, military assistance has no effect on violence in established, non-personalist regimes. The article develops a novel theory of how regime characteristics condition responses to external military support, and identifies a distinct mechanism through which military aid increases domestic political violence.
