The post-1945 period of bipolarity has been remarkably stable, at least when measured by the standards of the first half of the century. But it has not been a period without tensions and major war stemming from passage through critical points on the power cycles of the major states. Yet, management of crisis internationally, combined with internal constraints on force use, has dampened the instability that followed these abrupt changes in power and role projections. Particularly since the 1960s, the system has found the capacity to assimilate the degree of structural change that has so far occurred.

Before assessing the individual cases of rapid structural change and their consequences for security and stability, three general observations regarding the application of power cycle theory are appropriate. First, the impact of rapid structural change on war is a probability: every instance of a crossing of a critical point will not necessarily lead to major war. Only the likelihood of major war increases.

Second, many manifestations of tension and strain short of war may reveal the onset of trouble for the system nonetheless. These manifestations may be contained, or they may break into confrontations which are violent and major. In either case, they reveal strains in the system that, if not resolved, may accumulate and lead to a more violent and systems-wide confrontation later. But even systems transformation does not have to end in warfare.