Since I wrote my initial chapter on national security for this volume more than twenty years ago, the concept's utility for studying American foreign policy has grown. Increasingly linked to the proliferating scholarship on and interest in grand strategy, the attractiveness of the national security paradigm stems from its synthetic qualities; its synthetic qualities arise from the fact that it is not a specific interpretation that focuses on a particular variable as much as a comprehensive framework that relates variables to one another and allows for diverse interpretations in particular periods and contexts.

National security policy encompasses the decisions and actions deemed imperative to protect domestic core values from external threats. This definition is important because it underscores the relation of the international environment to the internal situation in the United States and accentuates the importance of people's ideas and perceptions in constructing the nature of external dangers as well as the meaning of national identity and vital interests. Like grand strategy, the national security paradigm takes cognizance of the fluidity and contingency of events at home and abroad, encourages efforts to identify goals, priorities, and tradeoffs, and focuses on means, resources, and ends.

By encouraging students of American foreign policy to examine both the foreign and the domestic factors shaping policy, by obligating them to look at the structure of the international system as well as the domestic ideas and interests shaping policy, the national security approach seeks to overcome some of the great divides in the study of American diplomatic history. Heretofore, the most influential studies have stressed the moralistic or legalistic or idealistic strains in American foreign policy, or, alternatively, the quest for territorial expansion, commercial empire, and geopolitical influence. Recent accounts tend to reinforce such binaries, pitting America's quest for freedom, democracy, and human rights against its drive for hegemony and empire, although sometimes these divergent interpretive frames are reconciled by discussions of “empire for liberty” or “empire of liberty.” Generally, realist historians believe that diplomatic behavior responds (or should respond) to the distribution of power in the international system; most revisionist and corporatist scholars, and most historians who dwell on ideas and ideology, assume that domestic economic requirements, social and cultural forces, and political constituencies are of overwhelming importance.