This book is about national security strategy: what it is, what its objectives are, what problems it seeks to solve or at least manage, and what kinds of influences constrain and create opportunities for the development and implementation of strategies. The heart of the problem with which national security strategy deals is the series of threats-normally military, but increasingly semi- or nonmilitary in character-that the country must confront and somehow overcome or contain. When the original version of this book1 was published in 1988, the set of threats facing the United States was reasonably static-those problems associated with the Cold War confrontation with a communist world led by the Soviet Union-even if there were signs of change on the horizon. In the ensuing decade and a half, that configuration of problems largely dissolved, along with the concrete parameters within which we operated. In its place is a much more diffuse, shifting, and controversial set of problems that is simultaneously simple, compelling, and arguable. Making strategy is no longer a simple, straightforward process, if it ever were. The making and implementation of strategy at the national level is largely an exercise in risk management and risk reduction. Risk, at that level, is the difference between the threats posed to our security by our adversaries and our capabilities to counter or negate those threats. Assessing risk and resolving it has two primary dimensions. The first is the assessment of risk itself: what conditions represent threats to our security, and how serious are those threats relative to one another and to our safety? The answers to these questions are not mechanical and obvious but are the result of subjective human assessments based on different political and philosophical judgments about the world and our place in it. The other dimension is the adequacy of resources to counter the threats that we identify. In circumstances of plenty, where there are adequate resources (manpower, materiel, perceived will, etc.) to counter all threats, this is not a problem. In the real world, each of these dimensions presents a real set of issues, which we must acknowledge up front.