Abstract Amidst a tense geopolitical environment and a rapidly evolving security landscape, this study investigates the determinants of alliance cohesion within NATO from its founding in 1949, examining both micro (dyadic) cohesion and macro (systemic) cohesion. The analysis employs an original dataset of more than 22,000 observations and introduces a novel operationalization of alliance political cohesion. A central finding outlines the role of trade asymmetry, which is strongly associated with alliance political cohesion. The results indicate that the structure of economic interdependence reflects a hierarchical structure within the alliance, enabling dominant actors to exert influence and sustain alignment through asymmetric dependence. Simultaneously, regime similarity, while it enhances cohesion in the full NATO sample, it is associated with greater divergence in US–ally relations. This pattern reflects the constraining role of domestic political processes, public opinion, and societal preferences in democratic states, which can limit alignment with US strategic choices. Overall, the findings contribute to the political economy of alliances by providing new evidence on how hierarchies, economic structure and political institutions jointly shape alliance behavior.
Palaios et al. (Thu,) studied this question.