The cold war and the global balance of power. Post cold war era is shaped by the era that came before it. A lot of ir theory developed by studying the cold war. The rise and spread of nuclear weapons as a game changer . Us-russia relations are probably more tense now than they have been since the collapse of the ussr. Best recent example of a bipolar international system. Most common comparison: ancient greeks with athens and sparta. Rise of china, potential for new us-china bipolar system. The us and the ussr (soviet union) were allied against hitler during wwii. Estimated 60 million people dead -> 26 million soviets. Even with such enormous casualties, the war left the ussr the strongest military force on the european continent. Only force that could deter the ussr was the us. Ussr was the only force that stood in the way of american global hegemony. Rivalry was characterized by many different dimensions.