Do birds of a feather deter better? Cultural affinity and alliance deterrence

Using a new latent measure of cultural affinity in military alliances (1816–2011), this study shows that states are less likely to be targets of militarized disputes or wars if they are members of defensive alliances with more culturally similar states. The theory posits that alliances between culturally similar states are designed with rules and norms that reflect the community's shared interests, which helps the members handle intra-alliance conflicts, and strengthens the overall credibility of the agreements, deterring attacks on outside members. Empirical analyses of politically relevant dyads with alliance ties shows that cultural affinity provides deterrence benefits in alliances between democracies (e.g., NATO) or between autocracies (e.g., Arab League, Gulf Cooperation Council) and that the deterrence results are strongest for potential targets that are non-democratic.