Following the collapse of the old communist regimes, 28 post-communist countries chose from among three main foreign security arrangements: commonwealth of independent states (CIS)/collective security treaty organization (CSTO) membership, north atlantic treaty organization (NATO) membership, or neutrality. What explains these choices? We are most interested theoretically in the role played by regime type. The alliances literature typically uses a narrow institutional theory of the effects of regime type, which implies that more democratic regimes are more attractive alliance partners than more authoritarian regimes. Post-communist area specialists will be aware that this institutional theory fails to explain the apparent tendency of more authoritarian post-communist regimes to join the CIS/CSTO. We develop a broader ideological theory of how regime type affects alliances, in which political institutions are complemented by substantive ideological and policy goals. Applying the ideological approach to the...