The view is here advanced that war is a political institution in process-an institution whose function has not been defined, whose structure is not yet fixed. The attempt to put war into a biological category errs not so much from a failure to distinguish between social and biological aspects of war as from failure to distinguish between competition and conflict as different aspects of the “struggle for existence.” Competition may be regarded as an individuating or analytic process; conflict as an integrating process. Wars have provided the necessity for an organization of society which, for the purpose of collective action at least, has become immeasurably superior to the primitive horde. The state not only had its origin in war, but its chief function continues to be preparation for and execution of war. Where no common interests or “constitutional understandings” exist to make compromise possible, wars seem inevitable. Ideological wars turn out to be struggles for land because political control and sovereignty of territory is necessary to maintain the different ways of life represented by the parties to these conflicts. The function of war has been (i) to extend the area of peace, (2) to create within that area a political power capable of enforcing it, and(3) to establish an ideology which rationalizes and a cult which idealizes the new political and social order.