The book is a timely investigation into the European security policy dynamic from the perspective of actors engaged in the contentious policy process. Instead of looking at security actors in isolation from one another, the book enquires into the practice of the policy process and maps out the constellations of formal and informal actors sponsoring concrete ideas on what European security should be about. The understandings of security shift and advocating a particular reading of security involves entering the political contest with actors advancing different conceptions. The contributors analyse these different modalities, overlapping scenes and shifting meanings that bring about EU security policies. Our case studies illustrate how these processes unfold both at the intra-EU level, where different institutions supply and endorse their security framings, and vis-à-vis the EU and its neighbours. The purpose of the book is to uncover, by pluralistic means, the rules of the game that structure the field of the EU’s security making. That way, rather than impose a rigid theoretical model, the editors structure the inquiry around three concepts: security, politics, and policy. This book was published as a special issue of Perspectives on European Politics and Society.