The principal characteristic of twenty-first-century international relations is turning out to be nonpolarity: a world dominated not by one or two or even several states but rather by dozens of actors possessing and exercising various kinds of power. This represents a tectonic shift from the past.
The twentieth century started out distinctly multipolar. But after almost 50 years, two world wars, and many smaller conflicts, a bipolar system emerged. Then, with the end of the Cold War and the demise of the Soviet Union, bipolarity gave way to unipolarity -- an international system dominated by one power, in this case the United States. But today power is diffuse, and the onset of nonpolarity raises a number of important questions. How does nonpolarity differ from other forms of international order? How and why did it materialize? What are its likely consequences? And how should the United States respond?
NEWER WORLD ORDER
In contrast to multipolarity -- which involves several distinct poles or concentrations of power -- a nonpolar international system is characterized by numerous centers with meaningful power.
In a multipolar system, no power dominates, or the system will become unipolar. Nor do concentrations of power revolve around two positions, or the system will become bipolar. Multipolar systems can be cooperative, even assuming the form of a concert of powers, in which a few major powers work together on setting the rules of the game and disciplining those who violate them. They can also be more competitive, revolving around a balance of power, or conflictual, when the balance breaks down.
At first glance, the world today may appear to be multipolar. The major powers -- China, the European Union (EU), India, Japan, Russia, and the United States -- contain just over half the world's people and account for 75 percent of global GDP and 80 percent of global defense spending. Appearances, however, can be deceiving. Today's world differs in a fundamental way from one of classic multipolarity: there are many more power centers, and quite