The aftermath of World War II was dominated by the Cold War (1947–1991), a geopolitical rivalry between the United States and its Western allies and the Soviet Union and its Eastern bloc. Winston Churchill famously described the ideological division as an "Iron Curtain" in 1946. The Marshall Plan (1948), a U.S. program providing over $12 billion in economic aid, helped rebuild Western Europe after WWII and prevented the spread of communism. Tensions reached flashpoints in conflicts like the Korean War (1950–1953), which ended in an armistice but no peace treaty, leaving Korea divided at the 38th parallel, and the Cuban Missile Crisis of October 1962, a 13-day confrontation over Soviet nuclear missiles in Cuba that was the closest the Cold War came to nuclear war. The two superpowers also competed in the Space Race (1957–1969), which saw milestones such as Sputnik (1957), Yuri Gagarin's flight (1961), and the Apollo 11 moon landing (1969). The fall of the Berlin Wall on November 9, 1989, the barrier that had divided East and West Berlin since 1961, symbolized the end of the Cold War.
While the Cold War raged, the world was transformed by decolonization (1940s–1970s), as European colonial powers granted independence to colonies in Africa, Asia, and the Caribbean, driven by nationalist movements, war exhaustion, and changing international attitudes. In India, Mahatma Gandhi (1869–1948) led a nonviolent independence movement against British rule through civil disobedience and peaceful protest, methods that inspired civil rights movements worldwide. India gained independence in 1947, but partition divided British India into Hindu-majority India and Muslim-majority Pakistan, causing massive communal violence and displacing 10–20 million people. Meanwhile, the Chinese Communist Revolution (1949) brought Mao Zedong (1893–1976) and the Communist Party to power, establishing the People's Republic of China, while the Nationalists under Chiang Kai-shek fled to Taiwan. Mao's policies, including the Great Leap Forward and the Cultural Revolution, transformed China into a major communist power but caused millions of deaths. The Vietnam War (1955–1975) between communist North Vietnam and U.S.-backed South Vietnam ended with communist victory and reunification in 1975.
The late 20th century also saw profound social and political change. In the United States, the Civil Rights Movement of the 1950s and 1960s fought to end racial segregation and discrimination against African Americans. Led by Martin Luther King Jr. (1929–1968), who advocated nonviolent protest and delivered the famous "I Have a Dream" speech, the movement achieved the Civil Rights Act (1964) and the Voting Rights Act (1965). In South Africa, the apartheid system of racial segregation (1948–1994) was dismantled through internal resistance and international pressure, leading to Nelson Mandela's (1918–2013) election as the country's first Black president in 1994. The Middle East was repeatedly reshaped by conflicts like the Six-Day War (1967), the Iranian Revolution (1979), and the Camp David Accords (1978), which produced the first peace agreement between Israel and an Arab state.
Catastrophes like the Chernobyl disaster of April 26, 1986, the worst nuclear accident in history, and the Rwandan Genocide (April–July 1994), which killed approximately 800,000 Tutsis and moderate Hutus over roughly 100 days, exposed the fragility of international institutions. The Soviet Union itself collapsed in 1991 under the weight of economic stagnation, the failed August coup, nationalist movements within its republics, and the reforms of Mikhail Gorbachev (glasnost and perestroika). New institutions like the European Union, formally established by the Maastricht Treaty in 1993, sought to bind nations together economically and politically. Yet the modern era also brought new terrors: the September 11, 2001 attacks, in which al-Qaeda hijackers killed nearly 3,000 people at the World Trade Center and Pentagon, triggered the U.S. War on Terror, invasions of Afghanistan and Iraq, and sweeping global security changes that continue to shape the world today.