Structural realism and the problem of polarity and war
The demise of the Soviet Union between 1989 and 1991 and the continuing and even growing material pre-eminence of the USA throughout the 1990s and into the new millennium is thought by some to have caused a funda- mental shift in the structure of the international system from bipolarity to unipolarity. This presumed shift in structure, it is also sometimes believed, means that, since bipolarity between 1945 and 1989/91 showed itself to be more conducive to peace than had multipolarity prior to 1945, unipolarity might be an even stronger force for peace among the great powers in the years ahead.1 American foreign policy itself seems to reflect the idea that US unipolarity is a force for global peace and is something, therefore, that needs to be preserved and, indeed, enhanced.2 In light of this presumed relationship between polarity and the likelihood of war, scholars and policy analysts have devoted themselves to three key questions: will American unipolarity produce an even more peaceful world than that achieved during the Cold War, will US unipolarity be undermined by the counteractions by individual lesser states or by balancing coalitions of such states, and can American policy itself extend US unipolarity or will it bring into being counter-balancing by other states?3
