Uniting the contributions to this volume is a common perspective on contemporary national security. While the types of participation in security activities are changing, the main purposes of actors making such a contribution remain largely consistent with one general proposition: that although security policy-making now features more actors, their agendas tend to be instrumentalised through conventional rubrics about the national interest. At the same time, normative values are intersecting with material considerations; non-traditional threats are meeting old ones; and new actors are challenging established elites in ways that often seem mystifying. Making sense out of the complex milieu of national security theories, actors and issues policy is therefore a main objective of this volume.