This handbook provides a comprehensive analysis of the contemporary theory, practice and themes in the study of national security. Part 1: Theories examines how national security has been conceptualised and formulated within the disciplines international relations, security studies and public policy. Part 2: Actors shifts the focus of the volume from these disciplinary concerns to consideration of how core actors in international affairs have conceptualised and practiced national security over time. Part 3: Issues then provides in-depth analysis of how individual security issues have been incorporated into prevailing scholarly and policy paradigms on national security. While security now seems an all-encompassing phenomenon, one general proposition still holds: national interests and the nation-state remain central to unlocking security puzzles. As normative values intersect with raw power; as new threats meet old ones; and as new actors challenge established elites, making sense out of the complex milieu of security theories, actors, and issues is a crucial task - and is the main accomplishment of this book.