Two ideas motivated this anthology of articles published in our quarterly, the Naval War College Review. First, the U.S. Navy is today at a critical point in its history. At a time when the nation is at war-with campaigns in two countries and engagements across the globe as part of the war on terror-the roles and missions traditionally assigned to the Navy have been called into question. Budget pressures have forced the service to reevaluate shipbuilding plans for several ships, including the DD(X) family. Second, it has been nearly ten years since selections from the Review have been compiled in a single, easily accessible volume; in that time there have appeared a number of articles that particularly deserve a second or third look by those who study and practice national security and naval affairs. The articles in this volume speak directly to the Navy's evolving role in the national and military strategies. The collection should serve as a handy reference for scholars, analysts, practitioners, and general readers interested in naval issues, and also that it will be useful for adoption as a reading by national security courses both in the United States and abroad. While the articles here certainly do not exhaust the range of views and important issues involving naval operations, strategy, or tactics, they do form a foundation for those interested in learning more. Moreover, they have enduring value; the perspectives and analyses they offer will not go out of fashion. The articles are reprinted exactly as they originally appeared, except that: proofreading errors noticed since original publication have been silently corrected; biographical notes have been updated; copyrighted art has been omitted; citation format (which evolved over the years) has been standardized in certain respects; and one author has appended a brief commentary. The volume is divided into three sections. The first introduces the changing security environment facing the United States and, by extension, the U.S. Navy. The articles examine both the external position of the nation and the emerging internal political and institutional contexts that constrain military and naval policies and decision making. The second part looks specifically at the roles and missions of the Navy at the beginning of the twenty-first century. Its articles cover both long-standing issues, such as forward presence, and the new missions the Navy has assumed in recent years-from projecting power far inland to providing theater and national missile defense, especially against opponents armed with nuclear, biological, or chemical weapons. The last part of the volume concentrates on military and naval transformation. The articles in this section provide some perspective on, perhaps even ballast for, the claims of proponents of the revolution in military affairs. Finally, I supply a conclusion reviewing the main themes of the articles and the avenues to which they point. The Naval War College Review remains one of the premier journals dedicated to publishing articles and essays with a naval and maritime focus. The chapters in the volume provide many of the intellectual building blocks for a maritime strategy designed to maintain American primacy and, if mandated by political leaderships, support a liberal empire that helps protect and spread the ideals of democracy and markets. The Navy's role will be arduous, and the need for continuous adjustments to the prevailing international security environment great. By reading or rereading the chapters that follow, specialists and nonspecialists alike can gain greater insights into the challenges ahead.