Hegemonic Stability Theorists believe that a dominant power preserves peace by dampening down potential conflicts. However, critics say that the dominant power often uses the system to advance its own interests, sometimes starts wars for its own purposes, supports proxy wars or is challenged by a rising power. For instance, Britain was dominant in the 1800s, but it had one big war with Russia in Crimea and constant wars in its colonies. The U.S. was dominant after the USSR collapsed in 1991, but it got bogged down in the Afghanistan and Iraq wars.
There are similar arguments about bipolar systems. For instance, in 1945 the U.S. was the only major power not destroyed by WWII and the only power possessing the atomic bomb. With everyone else in ruins, the U.S. economy accounted for 50% of world industrial and agricultural production. However, the USSR had occupied Eastern Europe during the war, had three times as many troops in Europe as the U.S., and obtained the atomic bomb through its spies within a few years.
Each side tried to steal allies away from the other and hang on to their own. However, Hegemonic Stability Theorists point out that each side also worked to prevent an outbreak of outright war between them because of the huge casualties that would result from the probable use of nuclear weapons. HST advocates say that this is the usual behavior of dominant powers, who generally work to prevent major conflicts. However, critics point out that during the Cold War, each side also supported proxies in various conflicts, notably the Korean War (1950-2) and the Vietnam War (1964-73), not to mention Angola, Mozambique and other conflicts.
After the USSR collapsed in 1991, the ‘stability’ of the Cold War era was followed by a short period in which the U.S. enjoyed military, economic and political dominance. Some U.S. commentators predicted a long period of unipolar American-enforced peace. However, countervailing forces quickly arose. As China’s economy boomed, it began to improve its military, build overseas bases and claim territory more aggressively. Without the threat of the USSR, NATO and other allies increasingly developed independent policies reflecting their own national interests.
Arguments about the configuration of current world system reflect that the U.S. military, albeit weakened by the Iraq war, is still far more powerful than anyone else. However, the political opposition of rivals (China, Russia, Iran) and sometimes even nominal allies like France, and the economic problems facing the U.S., such as big trade and budget deficits and economic competition from China, suggest an emerging multipolar system.