Over the next two decades, international politics will be shaped by whether the international system remains unipolar or is transformed into a multipolar system. Can the United States sustain its primacy? Or will the emergence of new great powers reorder the distribution of power in the international system?

The United States is the sole superpower in a unipolar world. How long this situation will last, however, is unclear. Although no new great military powers have emerged to balance against the United States, second-tier states are engaging in subtle, nontraditional forms of balancing that could lead to the end of unipolarity. Analysts who focus exclusively on traditional forms of balancing should not be surprised when the United States finds itself unable to maintain its unipolar position in a changing world.