Intelligence has never played a more prominent role in international politics than it does at the opening of the twenty-first century. National intelligence services are larger than ever and play a more public role than ever before in policy making process of most states. Public discussion of intelligence has become commonplace in political discourse on international issues.This major reference collection covers all aspects of the role of intelligence in national as well as international politics, as a tool to inform decision-making as well as a tool in the execution of policy. Volume One introduces a range of key concepts and theories that lie at the centre of the study of intelligence. Volume Two focuses on the challenges of intelligence analysis. Volume Three addresses issues related to security intelligence, deception and the increasingly prominent issue of international intelligence cooperation. Volume Four addresses the legal and ethical implications of intelligence practices for liberal democracies in particular. Volume Five introduces readers to the nature of military intelligence before examining in detail the role of intelligence in military command.