This edition of the U. S. Army War College Guide to National Security Policy and Strategy continues to reflect the structure and approach of the core national security strategy and policy curriculum at the War College. The fourth edition is published in two volumes that correspond roughly to the Department of National Security and Strategy’s core courses: “Theory of War and Strategy” and “National Security Policy and Strategy.” Like previous editions, this one is largely an expansion of its predecessor rather than a major rewriting. About a quarter of the chapters are new, and several others have undergone significant rewrites or updates. However, approximately half of the book remains unchanged. Although this is not primarily a textbook, it does reflect both the method and manner we use to teach strategy formulation to America’s future senior leaders. The book is not a comprehensive or exhaustive treatment of either strategic theory or the policymaking process. Both volumes are organized to proceed from the general to the specific. Thus the first volume opens with general thoughts on the nature and theory of war and strategy, proceeds to look at the complex aspect of power, and concludes with specific theoretical issues. Similarly, the second volume begins by examining the policy/strategy process, moves to a look at the strategic environment, and concludes with some specific issues. This edition adds several short case studies that can be used to illustrate the primary material in the volume.