Introductory. At this time nearly all serious minds are preoccupied with the problem how, after the European war, peace may be most effectively promoted and maintained. Thoughts are turned toward the question what is the best international system for the sustenance of higher international justice—a revitalized Concert of Europe, or of the world, or some new application of the “balance of power” principle. There are those who consider the “balance of power” doctrine to have outlived its usefulness, and to have shown itself productive of mischief; others would retain or reconstruct existing alliances in a form more efficacious for the preservation of international peace. Statesmanship will have to face many other difficult problems of international relationship after the war, and internationalists will be impelled to give a greatly increased share of their attention to the sanctions of international law and to the political conditions essential to its maintenance and development. Such questions call for an understanding of aspects of the life of the international community that are now much more strongly accentuated than they were before the war, and that can scarcely fail to attract scientific study to factors in the general situation the importance of which till recently was underrated. These practical problems demand in some degree philosophical study of the structure of the international community; as pure science precedes applied science, the communal life of States must be analyzed before light can be thrown on the issues of practical statecraft. The question how international force is to be organized, so as to render most effective aid to the cause of justice, presupposes for its satisfactory solution an inquiry into the actual constitution of the international society. States, moreover, can wisely order their future only by acting with full knowledge of the lessons of history. The interpretation of history is a necessary point of departure for the statesman and the publicist, if they are to offer sound proposals for practical action. But one is powerless to extract any meaning from history without understanding the social processes of which conspicuous historical events are but the surface manifestations. One must read history in the light of political science to grasp its meaning. Thus we are led inevitably, as a preliminary to any practical program, or to any interpretation of recent history, to the task of surveying the actual distribution, transformation, and organization of international force, and of stating in analytical terms the relation between these processes and the maintenance of international right—that is, order and justice. The conceptions of international force and of international power are so closely related as to be almost identical, but in this investigation we prefer the concept of force as something more positive and more tangible than power, which is latent force, or that which may develop actual force. For this reason the propositions here elaborated apply equally to the organization of international power—to the establishment of that authority through which the supremacy of law is effectuated and secured.