AbstractScholars and policymakers agree that major powers have leverage over their more junior partners. Giving security assistance or providing arms is supposed to increase this leverage. However, major powers often hit roadblocks when trying to influence the behaviour of their junior partners. This article demonstrates that junior partners are often successful in constraining the behaviour of the major power partners, and have particular success in extracting additional resources from their major partners. This article develops the concept of loyalty coercion to explain that leverage is based on rhetorical and symbolic moves, rather than material preponderance. It then uses cases of US arms sales to show that weapons transfers did not lead to US leverage, instead opened opportunities for junior partner influence. The article contributes to scholarly and policy perspectives on alliance management and reputation, and leverage in world politics.