This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book introduces some of the core ideas surrounding development and security in the contemporary world. The truism that development requires security and security requires development has become firmly entrenched in the lexicon of statebuilding. The book focuses on the best of recent academic theory, field research and policy developments to provide an overview of the connections between security and development, before, during and after conflict. It explores the implications of these connections for the theory and practice of development and the ways different actors have sought to manage and resolve conflict in the South. The book focuses on the politics of development actors and how people 'doing development' operate in conflict and post-conflict areas, concentrating on non-combat organisations operating in these areas and the process of 'securitisation'.