Countries interested in the promotion of political development often provide aid in the form of democracy assistance. However, some regimes resist these attempts to promote democracy, introducing repressive measures to counteract their effectiveness. Hence, democracy assistance sometimes has the unintended consequence of curtailing democracy. This article explains how the size of the targeted regime’s military determines the effectiveness of democracy assistance and why it can sometimes result in lower levels of political freedom. Large militaries, often holding a privileged position in authoritarian regimes, will be threatened by political liberalization and its associated redistribution of resources. They will thus work with the regime to limit the effect of democracy assistance, while their size makes this repression more feasible. In states with smaller militaries, regimes have less incentive and capacity for repression, and democracy assistance is more successful at empowering democratic opposition. Cross-national statistical analysis of the United States Agency for International Development democracy assistance supports the argument.