During the era of détente, Soviet and US leaders pursued common interests in controlling the spread of nuclear weapons, limiting the cost of the arms race, and expanding trade. Summit meetings brought agreements on nuclear non-proliferation, arms limitation, and space exploration. Yet, after a high point of friendly negotiation in the early 1970s, friction and competition overshadowed cooperation. While the unraveling of détente has often been blamed on Soviet adventurism in the “Third World,” this chapter presents a more balanced explanation. It notes that the United States too intervened around the world, argues that geopolitical competition was not the sole cause of tension, and highlights how domestic political dynamics disrupted relations between the superpowers. After the divisive and destructive US war in Vietnam, many Americans yearned to recover faith in their moral superiority. Denunciations of Soviet human rights violations, including restrictions on Jewish emigration and repression of dissidents, contributed to a revival of confidence in American virtues while irritating Soviet leaders. Long before the USSR invaded Afghanistan in 1979, acrimony eclipsed partnership.