Is Alliance Credibility Interdependent?

Do changes in the credibility of one alliance impact the credibility of other alliance commitments? Some observers believe that weak credibility in one alliance will undermine others, while others expect that allies pay more attention to their particular circumstances. This debate has continued for decades in part because systematic empirical evidence is rare. We address the debate with a new measure of alliance credibility based on expert surveys. We then test credibility interdependence in U.S. alliances with Gaussian process regression. We find that allied credibility perceptions within regions are strongly correlated, but there is little correlation between regions. These correlations reflect common unobservales and a small impact of shared perception of past U.S. behavior. Our findings advance scholarship on alliances and reputation by using a direct measure of alliance credibility, rather than indirect proxies that are often causes or effects of credibility.