Affective ties encompass a broad family of emotional phenomena, including love, affection, attachment, and devotion. Affective ties may appear deeply personal, and they most certainly are. But they are also important resources for the exercise of political power in international politics – not only as vulnerabilities that can be exploited for coercion but also, and more significantly, as means to mobilise action and sacrifice. Viewed from the vantage point of political agents, affective ties are thus power resources whose distribution in the international system shapes their strategies and choices. Viewed from the perspective of the system, the international realm is not only characterised by struggles over material capabilities or ideas but also competition over affective ties. Correspondingly, nationalism is not simply an identity. It is a collection of techniques and practices for generating and capturing affective ties that has emerged as a highly effective contender in this contest, with crucial implications for how the international system is organised. That being said, other forms of eliciting affective ties also persist.