Scholarship on NATO is often preoccupied with key episodes in the development of the organisation and so, for the most part, has remained inattentive to theory. This book addresses that gap in the literature. It provides a comprehensive analysis of NATO through a range of theoretical perspectives that includes realism, liberalism and constructivism, and lesser-known approaches centred on learning, public goods, securitisation and risk. Focusing on NATO’s post-Cold War development, it considers the conceptualisation, purpose and future of the Alliance. This book will be of interest to students and scholars of international organisation, international relations, security and European Politics.