A useful anticipation of defense economics must rest upon the dramatic, continuing, and confusing upheaval in the functions of military forces in the world of the coming century. This essay tries to reflect the staggering array of new features which impact on the provision of national defense and international security; as these profoundly shape the discipline of “defense economics,” they will elevate in importance the social, cultural, developmental, and legal interactions between economics and defense so that the subject will fit far more comfortably into the realm of political economy than it did when it originated decades ago. With this perspective in mind, this introduction is focused on categories defining the core of “defense economics” in the coming decades.