Both nations, however, were working within a framework conditioned by the past. Ultimately, the rivalry between the two superpowers stemmed from their different historical perspectives and their irreconcilable political ambitions. Intense competition for political and military supremacy had long been a regular feature of Western civilization. The United States and the Soviet Union were the heirs of that European tradition of power politics, and it should not surprise us that two such different systems would seek to extend their way of life to the rest of the world.