A model of world affairs is defined which identifies two interacting systems. The first system is called a nation state system, in which nations are the only actors. The second system is called an international system, in which there are many actors, from individuals to nations to international organizations and corporations. The world system is defined as the amalgam of these two. Within nations, the four functional requirements of Parsons are used to identify the economy as representative of the adaptation subsystem, the culture as representative of the integrative subsystem, individuals and families as representative of the pattern maintenance subsystem, and government as representative of the goal attainment sub system. An internation system is then specifically defined as interaction between the goal attainment subsystems of nations. A similar procedure is adopted for the inter national system. The three world arms races are then interpreted in the light of the model using the idea that the international component has been greater in each arms race than in the previous one. In this way it is possible to interpret the differences in behavior in each of the arms races in terms of the model. It is also found that the linkage between trade and defense has increased in each successive arms race. It is suggested that future analysis of world affairs should take into account other actors, such as international organizations and international corporations, as well as nations. Further, the importance of the integrative system is stressed and some sugges tions for strengthening it are put forward.