High School World History · 1945–1991
How the allies who beat Hitler became rivals, divided the world, built enough nuclear weapons to end it, and then, almost without a shot, stopped.
For more than forty years after World War II, the United States and the Soviet Union never fought each other directly. Yet their rivalry split Europe with a wall, sent rockets into space, and fueled wars in Korea, Vietnam, Afghanistan, and many other places where millions of people died.
I am Herodotus. In my day, the Greeks and Persians fought with spears. In this conflict, the two greatest powers on Earth fought with alliances, money, spies, propaganda, and the threat of weapons so terrible that neither dared to use them. Why did they become enemies? How close did they come to nuclear war? And why did it all end so suddenly?
The Cold War was a rivalry, from about 1945 to 1991, between the United States and its allies, who favored democracy and capitalism, and the Soviet Union and its allies, ruled by communist parties. It was "cold" because the two superpowers never fought a full war against each other. Instead they raced to build nuclear weapons, competed for allies, and backed opposite sides in "hot" wars around the world.
It ended when communist rule collapsed in Eastern Europe in 1989, Germany reunified on October 3, 1990, and the Soviet Union itself broke apart in December 1991.
The United States, Britain, and the Soviet Union fought together to defeat Nazi Germany, but they had never trusted each other. The Soviet leader, Joseph Stalin, ran a communist dictatorship in which the state owned farms and factories and one party ruled. The Americans and British wanted democracies with free elections and open markets. Once their common enemy was gone, those differences came to the surface.
Meeting in the Crimea while the war was still on, the "Big Three" agreed to divide a defeated Germany into zones of occupation, to set up the United Nations, and that the Soviet Union would join the war against Japan. Stalin promised free elections in the lands his armies freed from the Nazis, including Poland. Those elections were never truly free.
After Germany's surrender, the leaders met outside Berlin. They confirmed the four zones of Germany (American, British, French, and Soviet), with Berlin, deep inside the Soviet zone, also split four ways. They argued over reparations and over Poland's new borders. President Harry S. Truman told Stalin that the United States had a powerful new weapon.
The Red Army stayed in the countries it had occupied. With Soviet backing, communist parties took over Poland, Romania, Bulgaria, Hungary, and, in February 1948, Czechoslovakia. On March 5, 1946, at Fulton, Missouri, Winston Churchill warned that "From Stettin in the Baltic to Trieste in the Adriatic an iron curtain has descended across the Continent."
In a long telegram from Moscow in February 1946, and in an anonymous 1947 article signed "X," Kennan argued that the Soviet Union would keep pushing outward unless it was firmly resisted. He called for "long-term, patient but firm and vigilant containment" of Soviet expansion. Containment became the basic US strategy for the rest of the Cold War.
In early 1947, Britain told the United States it could no longer afford to support the governments of Greece, which was fighting a civil war against communist guerrillas, and Turkey, which was under Soviet pressure. On March 12, 1947, Truman asked Congress for $400 million in aid for the two countries. He declared that the United States must "support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures." This promise became known as the Truman Doctrine.
Western Europe was still in ruins, and leaders feared that hunger and unemployment would help communist parties win power. On June 5, 1947, Secretary of State George C. Marshall proposed a huge recovery program. Under the Marshall Plan, signed into law on April 3, 1948, the United States gave Western European countries about $12 billion to $13 billion in aid over four years. Stalin refused to let the Soviet Union or the countries it controlled take part.
In June 1948, the Americans, British, and French introduced a new currency, the Deutsche Mark, in their zones of Germany and West Berlin, a step toward a separate West German state. Stalin answered on June 24, 1948, by cutting every road, rail, and canal link between West Berlin and the West. More than two million West Berliners were left with only about a month's supply of food.
Rather than force their way in by land and risk war, the Western allies supplied the city by air. In the Berlin Airlift, American and British planes flew in food, coal, and medicine around the clock. At the busiest times, a plane landed in West Berlin about every minute. The Soviets lifted the blockade in May 1949, and the airlift continued until September 30, 1949. In all, the planes carried about 2.3 million tons of supplies.
The crisis made the division of Germany permanent. The Federal Republic of Germany (West Germany) was founded on May 23, 1949, with its capital at Bonn. The Soviet zone became the German Democratic Republic (East Germany) on October 7, 1949.
On April 4, 1949, twelve countries signed the North Atlantic Treaty, creating NATO. Its key promise, in Article 5, was that an armed attack on one member would be treated as an attack on them all. For the United States, it was the first peacetime military alliance outside the Western Hemisphere. West Germany joined NATO on May 9, 1955. Five days later, on May 14, 1955, the Soviet Union and seven communist states in Eastern Europe signed the Warsaw Pact.
Some European countries joined neither alliance, including Sweden, Finland, Switzerland, Austria, Ireland, and Yugoslavia, a communist state that broke with Stalin in 1948.
After Japan's defeat, China's civil war resumed between the Nationalists of Chiang Kai-shek, backed by the United States, and the Communists of Mao Zedong. The Communists won. On October 1, 1949, Mao proclaimed the People's Republic of China in Beijing, and Chiang's government fled to the island of Taiwan. With the world's most populous country now communist, many Americans asked angrily who had "lost China." In February 1950, Mao and Stalin signed a treaty of alliance.
Korea had been split at the 38th parallel in 1945, with Soviet troops in the north and American troops in the south. With Stalin's approval, North Korea's Kim Il Sung invaded the South. The UN Security Council, which the Soviets were boycotting, called on members to help South Korea. US-led UN forces under General Douglas MacArthur landed at Inchon in September 1950 and pushed north toward the Chinese border. In October, hundreds of thousands of Chinese troops crossed into Korea and drove them back. The war became a stalemate near the 38th parallel. An armistice was signed in 1953, but no peace treaty ever followed, and Korea is still divided.
Korea changed the Cold War. In 1950, the secret US policy paper NSC-68 had called for a huge military buildup to contain communism everywhere. The Korean War made that buildup happen: between 1950 and 1953, US defense spending almost tripled as a share of the economy, from 5 to 14.2 percent of GDP, and the United States took on new commitments to defend Taiwan, Japan, and the French war against communist forces in Indochina.
The United States dropped the first atomic bombs on Japan in August 1945. Its monopoly lasted only four years: the Soviet Union tested its own atomic bomb on August 29, 1949, helped by information from spies inside the American bomb project. Both sides then built hydrogen bombs, hundreds of times more powerful. The United States tested the first one, "Ivy Mike," on November 1, 1952, and the Soviets tested their own H-bomb designs in 1953 and 1955.
Next came the means to deliver them: long-range bombers, then intercontinental ballistic missiles (ICBMs) that could cross the world in about half an hour, then missiles fired from submarines. By the 1960s, each side could destroy the other even after being hit first. This situation became known as mutually assured destruction, or MAD. It was terrifying, but many historians think it also made both sides more careful.
US figures are official counts of the active and inactive stockpile from the US Department of Energy and Department of State. The Soviet Union never published its numbers, so its figure is an estimate by independent researchers; published estimates range from about 40,000 to 45,000. The Soviet bar is drawn at the middle of that range.
The Soviets launched Sputnik 1, the first artificial satellite, a metal ball about the size of a beach ball that circled the Earth about every 98 minutes, beeping a radio signal. Americans were shocked: a rocket that could put a satellite in orbit could also carry a nuclear warhead. In 1958, Congress created NASA and passed the National Defense Education Act to pay for science and math education.
Gagarin orbited the Earth once in his Vostok 1 capsule, another Soviet first. Six weeks later, on May 25, 1961, President John F. Kennedy asked Congress to commit the United States to landing a man on the Moon and returning him safely to Earth before the decade was out.
On the Apollo 11 mission, Armstrong and Aldrin landed on the Moon while Michael Collins orbited above. Hundreds of millions of people around the world watched on television. In 1975, an American Apollo spacecraft and a Soviet Soyuz docked in orbit, a symbol of the easing of tensions called détente.
Stalin died in March 1953. In February 1956, the new Soviet leader, Nikita Khrushchev, shocked communists by denouncing Stalin's crimes in a "secret speech." Many people in Eastern Europe hoped that Soviet control would loosen. They soon learned its limits.
Students and workers rose up against Hungary's communist government. The reform communist Imre Nagy became prime minister and announced that Hungary would leave the Warsaw Pact. On November 4, Soviet tanks crushed the revolution. About 2,500 Hungarians were killed, some 200,000 fled abroad, and Nagy was later executed. The United States, which had encouraged resistance to Soviet rule in its radio broadcasts, did not intervene.
Between 1949 and 1961, more than 2.5 million East Germans fled to the West, many of them young and skilled, most through the open border in Berlin. Overnight on August 13, 1961, East German troops and police sealed it with barbed wire, soon replaced by a concrete wall with watchtowers and a "death strip." For 28 years, the Berlin Wall was the most famous symbol of the Cold War.
Czechoslovakia's new communist leader, Alexander Dubček, promised "socialism with a human face": freer speech and less censorship. On the night of August 20–21, 1968, Warsaw Pact troops invaded and ended the reforms. Soviet leader Leonid Brezhnev claimed the right to intervene wherever communist rule was threatened, a claim the West called the Brezhnev Doctrine.
In 1959, Fidel Castro took power in Cuba, just 90 miles from Florida, and soon allied with the Soviet Union. In April 1961, a CIA-trained force of Cuban exiles landed at the Bay of Pigs to overthrow him and was quickly defeated. Khrushchev then secretly sent nuclear missiles to Cuba, partly to protect Castro and partly to balance American missiles near the Soviet Union, including in Turkey.
On October 14, 1962, an American U-2 spy plane photographed missile sites under construction. After a week of secret debate, Kennedy announced on October 22 that the US Navy would "quarantine" Cuba, stopping ships carrying weapons. For the next six days, the world came closer to nuclear war than ever before or since. On October 27, a U-2 was shot down over Cuba and its pilot killed. On October 28, Khrushchev agreed to remove the missiles in return for a US promise not to invade Cuba. In a secret part of the deal, the United States also agreed to remove its missiles from Turkey.
Both sides were shaken. In 1963, they set up a direct "hotline" between Washington and Moscow and signed the Limited Test Ban Treaty, which ended nuclear tests in the atmosphere, in space, and under water.
After 1945, the old European empires broke up. Between 1945 and 1960, about three dozen new countries in Asia and Africa won independence, and by the 1970s most of the rest had followed. Both superpowers competed for the friendship of these new states, offering aid, weapons, and advisers. Many new nations refused to pick a side: at Bandung, Indonesia, in 1955, Asian and African leaders met to chart their own course, and in 1961 they founded the Non-Aligned Movement.
Where the superpowers did take sides, local struggles often became proxy wars, in which each superpower armed and funded one side while avoiding direct war with the other.
Vietnamese communists led by Ho Chi Minh fought French colonial rule and won at Dien Bien Phu in 1954. A peace conference at Geneva split Vietnam at the 17th parallel, with a communist North and a US-backed South. Elections to reunite the country were promised for 1956 but never held. American leaders believed in the domino theory: if South Vietnam fell to communism, its neighbors would fall one after another.
The United States sent money, then advisers, then, after the Gulf of Tonkin Resolution of August 1964, combat troops. By 1968, more than 500,000 Americans were in Vietnam. The North Vietnamese and Viet Cong Tet Offensive, launched in January 1968, failed militarily but convinced many Americans the war could not be won quickly. Protests grew at home. President Richard Nixon withdrew US troops gradually, and the Paris Peace Accords of January 1973 ended direct American fighting. On April 30, 1975, North Vietnamese forces captured Saigon, and Vietnam was reunited under communist rule. Laos and Cambodia also came under communist rule in 1975.
The Congo won independence from Belgium on June 30, 1960, and quickly fell into civil war. Prime Minister Patrice Lumumba asked the Soviets for help. He was overthrown and, in January 1961, murdered. The army officer Joseph Mobutu, backed by the United States, seized power in November 1965 and ruled for 32 years.
When Portugal gave up Angola in 1975, rival independence movements fought for power. The Soviet Union and thousands of Cuban troops backed the Marxist MPLA, while the United States and South Africa backed its rivals. In the Ogaden War of 1977–1978, Soviet weapons and Cuban troops helped Ethiopia's Marxist government drive back an invasion by Somalia.
The United States treated Latin America as its own sphere. The CIA helped overthrow elected governments it saw as leftist, in Guatemala in 1954, and supported opponents of Chile's socialist president, Salvador Allende, before a military coup in 1973. In Nicaragua, the United States armed the "contra" rebels against the leftist Sandinista government from 1981 until a 1990 election ended the war.
In late December 1979, Soviet troops invaded Afghanistan to prop up its communist government. The United States, Pakistan, Saudi Arabia, and others armed the Muslim guerrilla fighters, the mujahideen. About 15,000 Soviet soldiers died before the last troops left on February 15, 1989. Estimates of Afghan deaths, most of them civilians, start at about 1 million, and about 5 million Afghans fled abroad.
By the late 1960s, both superpowers had reasons to ease tensions. The United States was worn down by Vietnam, and the Soviet Union had split bitterly with China, its former ally. This period of relaxed tensions is called détente, a French word for loosening.
Nixon, long known as a fierce anticommunist, became the first US president to visit the People's Republic of China. He and Mao used the split between China and the Soviet Union to their advantage. The two countries set up full diplomatic relations in 1979.
Nixon and Brezhnev signed the first Strategic Arms Limitation Talks agreements. One froze the number of long-range missile launchers each side had; the Anti-Ballistic Missile Treaty limited defenses against missiles, so that neither side could hope to survive a nuclear war by shooting down the other's missiles.
Thirty-five countries, including the United States, Canada, the Soviet Union, and almost every country in Europe, signed the Helsinki Final Act. The West accepted Europe's postwar borders. In return, the Soviet bloc promised to respect human rights. Dissidents in the East, such as the writers of Czechoslovakia's Charter 77, used those promises to hold their governments to account.
Détente did not last. The Soviets kept building missiles and backed revolutions in Africa. SALT II, signed in Vienna on June 18, 1979, was never ratified by the US Senate after the Soviet invasion of Afghanistan that December. President Jimmy Carter stopped grain sales to the Soviet Union and led a boycott of the 1980 Moscow Olympics.
President Ronald Reagan, elected in 1980, called the Soviet Union an "evil empire," greatly increased military spending, and in 1983 proposed the Strategic Defense Initiative, a plan for space-based missile defenses that critics nicknamed "Star Wars." Tensions rose higher than at any time since the early 1960s.
On March 11, 1985, Mikhail Gorbachev became leader of the Soviet Communist Party. At 54, he was much younger than the old men who had led before him, and he knew the Soviet economy was failing. Military spending, including the war in Afghanistan, was eating up money the country could not spare. Gorbachev tried two big reforms:
Gorbachev also wanted to end the arms race. After several summits, he and Reagan signed the Intermediate-Range Nuclear Forces (INF) Treaty on December 8, 1987, the first treaty to eliminate a whole class of nuclear weapons. Most important for Eastern Europe, Gorbachev let it be known that the Soviet Union would no longer send tanks to keep communist governments in power.
After talks with the government, Solidarity was legalized again and won almost every seat it was allowed to contest in Poland's elections of June 4, 1989. By September, Poland had its first non-communist prime minister since the 1940s. Hungary began taking down its border fence with Austria in May, and in September it let thousands of East Germans cross to the West.
In China, students and workers filled Beijing's Tiananmen Square for weeks to demand democracy and an end to corruption. On the night of June 3–4, the Communist government sent in the army, which fired on crowds in the streets around the square. Estimates of the dead range from several hundred to several thousand; China's government has never allowed an independent count. In China, unlike Europe, the Communist Party kept power.
After weeks of mass protests in East Germany, a confused announcement suggested that East Germans could travel freely, starting immediately. That night, huge crowds gathered at the Wall's checkpoints until the guards opened the gates. Berliners from both sides climbed onto the Wall and began chipping it apart.
In Czechoslovakia, the peaceful Velvet Revolution, begun by students on November 17, ended with the dissident playwright Václav Havel elected president in December. Bulgaria's longtime leader was pushed out. Only in Romania did the revolution turn bloody: the dictator Nicolae Ceaușescu was overthrown and, on December 25, executed.
Germany reunified on October 3, 1990, after the two German states and the four wartime Allies signed the Two Plus Four Treaty on September 12, 1990. United Germany remained in NATO. The Warsaw Pact was dissolved on July 1, 1991.
Inside the Soviet Union, nationalities long ruled from Moscow demanded independence, starting with Lithuania, Latvia, and Estonia. In August 1991, hard-line communists tried to overthrow Gorbachev. The coup collapsed in three days, in part because Boris Yeltsin, the elected president of the Russian republic, rallied crowds in Moscow against it. The republics then broke away one after another. Gorbachev resigned on December 25, 1991, and on December 26 the Soviet Union formally ceased to exist, replaced by 15 independent countries.
The Cold War ended without the nuclear war so many people had feared. But it left a long shadow. Korea is still divided, and China, Vietnam, Laos, Cuba, and North Korea are still ruled by communist parties. NATO did not disappear; since 1999 it has taken in many former Warsaw Pact countries and three former Soviet republics, a source of lasting tension with Russia. Thousands of nuclear weapons still exist. Many countries where proxy wars were fought, such as Afghanistan and Angola, faced years more of war after the superpowers left. Historians still debate whether the Cold War was won by Western strength and pressure, lost by a failing Soviet system, or ended by the choices of leaders like Gorbachev and Reagan, and of ordinary people in places like Gdańsk, Leipzig, and Prague.
Follow the Cold War from the meetings of the wartime allies to the end of the Soviet Union. Use the buttons to show one kind of event or one decade at a time.
Roosevelt, Churchill, and Stalin plan the occupation of Germany and the United Nations.
Truman, Stalin, and the British leaders confirm the four zones of Germany.
The United States uses the first atomic bomb; Nagasaki is bombed three days later.
A US diplomat in Moscow argues that Soviet expansion must be firmly resisted.
In Fulton, Missouri, Churchill warns that Europe has been divided.
Truman asks Congress for $400 million in aid for Greece and Turkey.
Secretary of State Marshall offers US aid to rebuild Europe.
The last democracy in Eastern Europe falls under communist rule.
Stalin cuts land routes to West Berlin; the Western allies start the Berlin Airlift.
Twelve countries sign the North Atlantic Treaty in Washington.
Land routes to West Berlin reopen; flights continue until September 30.
The American monopoly on the atomic bomb is over.
Mao Zedong proclaims a communist state in Beijing.
North Korea invades South Korea.
Chinese troops cross into Korea and drive UN forces south.
The United States tests "Ivy Mike" in the Pacific.
The fighting stops near the 38th parallel. No peace treaty is signed.
Vietnamese forces defeat the French, ending French rule in Indochina.
The Soviet Union and seven Eastern European states form an alliance.
About 2,500 Hungarians are killed and some 200,000 flee.
The Soviet Union launches the first artificial satellite.
Fidel Castro's rebels overthrow the dictator Fulgencio Batista.
The Congo Crisis begins within days.
He is the first human in space.
A CIA-trained force of Cuban exiles fails to overthrow Castro.
East Germany seals the border through Berlin.
Kennedy announces Soviet missiles in Cuba and a naval quarantine.
The United States promises not to invade Cuba.
Nuclear tests in the atmosphere, space, and under water are banned.
Congress gives the president broad power to wage war in Vietnam.
North Vietnamese and Viet Cong forces attack cities across South Vietnam.
Countries without nuclear weapons agree not to acquire them.
Warsaw Pact troops end the Prague Spring.
Apollo 11 astronauts Neil Armstrong and Buzz Aldrin walk on the Moon.
The first visit by a US president to the People's Republic of China.
Nixon and Brezhnev sign the first nuclear arms limits.
Direct US fighting in Vietnam ends.
North Vietnam conquers South Vietnam.
Thirty-five countries accept Europe's borders and promise to respect human rights.
Civil war follows, with Cuban troops on one side and South African troops on the other.
The US Senate never ratifies it.
Soviet troops enter the country in the last days of December.
Poland's government accepts the first independent trade union in the Soviet bloc.
Solidarity is banned and its leaders arrested.
Reagan proposes a missile defense system nicknamed "Star Wars."
He soon launches glasnost and perestroika.
A reactor explodes in Soviet Ukraine.
Reagan and Gorbachev agree to destroy a whole class of nuclear missiles.
The last Soviet troops leave.
The Chinese army fires on protesters in Beijing.
Solidarity wins almost every seat it is allowed to contest.
East Germans cross freely into West Berlin.
Peaceful protests end communist rule in Czechoslovakia.
Romania's communist dictator is overthrown in a violent revolution.
East Germany joins the Federal Republic.
The Soviet bloc's military alliance formally ends.
Hard-liners fail to overthrow Gorbachev.
A day after Gorbachev resigns, 15 independent countries take its place.
A primary source was made by people who lived through the events. Read each one closely and ask: Who made this? When? Why? Who was the audience?
"I believe that it must be the policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures."
Why it matters: Truman was asking for $400 million for Greece and Turkey, but he described the choice in global terms: "nearly every nation must choose between alternative ways of life." The National Archives notes that later presidents used similar reasoning to justify actions in Korea, Cuba, and Vietnam.
Think: Truman never names the Soviet Union in this sentence. Who do you think he meant by "armed minorities" and "outside pressures"? Why might he have avoided naming them?
"In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military-industrial complex. The potential for the disastrous rise of misplaced power exists and will persist."
Why it matters: Eisenhower, a five-star general who had commanded the Allied armies in World War II, warned that the arms race had created "a permanent armaments industry of vast proportions," something "new in the American experience." He believed it was necessary but dangerous.
Think: Why might this warning carry more weight coming from a former general than from a peace activist? Is the "military-industrial complex" a useful idea today?
"Freedom has many difficulties and democracy is not perfect, but we have never had to put a wall up to keep our people in, to prevent them from leaving us."
Why it matters: Kennedy spoke less than two years after the Berlin Wall went up, to a huge crowd in West Berlin. He ended with the famous words "Ich bin ein Berliner" ("I am a Berliner"), declaring that "all free men, wherever they may live, are citizens of Berlin."
Think: How does Kennedy turn the Wall into an argument for the West? Is it fair to judge a political system by whether its people are allowed to leave?
"General Secretary Gorbachev, if you seek peace, if you seek prosperity for the Soviet Union and Eastern Europe, if you seek liberalization: Come here to this gate! Mr. Gorbachev, open this gate! Mr. Gorbachev, tear down this wall!"
Why it matters: Reagan spoke 24 years after Kennedy, at a time when Gorbachev's reforms were beginning. In the same speech, he said East and West "do not mistrust each other because we are armed; we are armed because we mistrust each other." The Wall opened two and a half years later.
Think: Did Reagan's words help bring down the Wall, or did the Wall fall for other reasons? What evidence from this page supports your answer?
Ten questions. Choose an answer for each, then press Check my answers to see your score and an explanation for every question.
Credits: All illustrations, diagrams, and maps on this page are original artwork made for Jugami. Map coastlines and borders are based on public-domain Natural Earth data; Cold War borders, alliances, and conflict areas are approximate and simplified. Death tolls and other figures that vary by source are given as ranges, with the institutions whose estimates we use. The speeches by Presidents Truman, Eisenhower, Kennedy, and Reagan are US government works in the public domain. Churchill's "iron curtain" phrase is quoted briefly for teaching.