Detente, Gorbachev, and the fall of the Iron Curtain

By the 1970s, US-Soviet relations entered a period of detente, or eased tension: President Nixon's surprise 1972 visit to Communist China opened relations with Beijing and exploited a growing split between China and the Soviet Union, while SALT treaties began limiting the two superpowers' growth in nuclear arsenals. Tensions rose again in the late 1970s and early 1980s after the Soviet Union's costly 1979 invasion of Afghanistan (sometimes called "the USSR's Vietnam") and President Reagan's more confrontational stance, including sharp "evil empire" rhetoric, a major defense buildup, and the proposed Strategic Defense Initiative missile-defense program.

Everything changed after Mikhail Gorbachev became Soviet leader in 1985 and introduced glasnost ("openness," allowing more free speech and press) and perestroika ("restructuring," market-oriented economic reforms), intended to save and strengthen the Soviet system -- but instead, by allowing open criticism and encouraging independence movements, these reforms accelerated its collapse. In 1989, revolutions swept largely peacefully across Eastern Europe: Poland's Solidarity movement under Lech Walesa negotiated a transition to democracy, Czechoslovakia's "Velvet Revolution" removed communist rule almost bloodlessly, and the Berlin Wall itself fell on November 9, 1989, as crowds from both sides tore it down by hand. Not every 1989 movement succeeded, however: that June, Chinese pro-democracy protesters in Beijing's Tiananmen Square were crushed by their own government rather than achieving reform, a stark reminder that the same year produced sharply different outcomes in different places. The Soviet Union itself formally dissolved in December 1991, Gorbachev resigned, and the Cold War that had shaped world affairs and threatened nuclear catastrophe for over four decades came to an end.