Unipolar, Bipolar, and Multipolar World Orders

International relations scholars classify the structure of the international system according to the number of great powers, or "poles," that dominate it at a given time, a framework most systematically developed by Kenneth Waltz in Theory of International Politics (1979). A unipolar system is one in which a single state possesses preponderant power across military, economic, and political dimensions with no comparable rival, a condition many scholars, including Charles Krauthammer in his 1990 Foreign Affairs essay "The Unipolar Moment," argued characterized the international system in the immediate aftermath of the 1991 collapse of the Soviet Union, when the United States possessed unmatched military reach, the world's largest economy, and no peer competitor across the full range of national power.