Your turn
Each lab is one step from the video. Open the border, drag the years, stack the causes.
Each lab isolates one idea from the video. The pressure gauge and the cause tower are simple models, not measurements.
Tap and slide, and watch what happens.
Tap the barrier or the button. What happens on the night of 9 November 1989?
East Germany opens its borders: the checkpoint that stood since 1961 lifts.
Tap the gate. Where do the people go?
Drag the years. When does the Iron Curtain appear, and when does it go?
NATO (1949), the Warsaw Pact (1955), the Wall (1961–1989), reunification (1990).
Slide it. Watch Europe split into two sides, then join again.
The curtain line is drawn roughly, as on Cold War maps.
Tap a year. How fast did the piles grow?
Strategic warheads in 1956; national peaks in 1967 (US) and about 1986 (USSR); world total about 70,300 in 1986.
Tap the buttons. Watch the piles grow!
Each disc is about 2,000 weapons. Sources: Britannica (arms race), Federation of American Scientists.
Switch the pressures on and off. Which push the needle hardest?
Economic strain plus glasnost and perestroika: reform released demands the system could not contain.
A simple model: the weights are illustrative, not measured.
Tap Poland and watch the row fall. Or knock them one by one.
Poland (June), Hungary's open border, East Germany (Nov), Czechoslovakia (Dec), Bulgaria, Romania.
Tap the first domino!
Stack the causes. Which would you give the most weight?
Historians remain divided over the underlying causes; most see several working together.
There is no single right answer: this is a debate historians still have.
Long ago, after a big war, two very big countries stopped trusting each other: America and the Soviet Union. Europe split into two sides, East and West.
The two sides never fought each other. A fight would have hurt everyone. So instead they raced: to build more weapons, and even to reach space.
A long wall split the city of Berlin in two. People on one side could not visit the other side.
A new Soviet leader, Mikhail Gorbachev, let people speak freely. He and America's President Reagan agreed to get rid of lots of weapons. Then, one after another, countries in the East chose new leaders, like dominoes falling. One night the Berlin Wall opened, and people hugged and cheered!
Germany became one country again. Then the Soviet Union split into lots of new countries. Leaders on both sides, and lots of ordinary people, helped end it.
The Cold War ended between 1989 and 1991, mostly without shots being fired between the two sides. The Soviet economy was failing.413 A new Soviet leader, Mikhail Gorbachev, allowed more free speech and reform, signed arms deals with US President Ronald Reagan, and decided the Soviet army would no longer prop up communist governments in Eastern Europe.414 In 1989 those governments fell one after another, and the Berlin Wall opened on 9 November 1989.14 Germany reunited in 1990, and on 25 December 1991 the Soviet Union itself broke apart into 15 countries.615
That's the surprise at the heart of the story: a rivalry between two superpowers armed with tens of thousands of nuclear weapons ended without the two of them ever going to war with each other.19
The Cold War was a long rivalry, from about 1947 to 1991, between the United States and its allies and the Soviet Union and its allies.1 Each side believed its way of running a country was right: the US stood for elections and a free-market economy, while the Soviet Union was a one-party communist state where the government ran the economy.
It was called "cold" because the two superpowers never fought each other directly. Instead the rivalry was fought with politics, money and propaganda,1 with an arms race, a space race, and proxy wars, where each superpower backed opposite sides in someone else's war.10
In World War II, the United States, Britain and the Soviet Union fought on the same side. But after Germany surrendered in May 1945, that uneasy alliance came apart.1 The Soviet army had pushed the Nazis out of Eastern Europe, and by 1948 the Soviets had set up communist governments across the region. The Soviets wanted a buffer against any future attack from Germany; the Americans and British feared Soviet control would spread into Western Europe.1
On 5 March 1946, in a speech in Fulton, Missouri, former British prime minister Winston Churchill said that "from Stettin in the Baltic to Trieste in the Adriatic, an iron curtain has descended across the Continent."2 In March 1947, President Truman promised US help to countries resisting communist takeovers (the Truman Doctrine).16 By 1947–48, with American Marshall Plan aid in the West and communist governments in the East, the split had hardened.1
| Year | What happened |
|---|---|
| 1945 | World War II ends in Europe; the wartime alliance starts to unravel1 |
| 1946 | Churchill's "iron curtain" speech2 |
| 1947 | Truman Doctrine; the East–West split hardens16 |
| 1948–49 | Soviet blockade of West Berlin; NATO is founded (1949); first Soviet atomic test (1949)1 |
| 1950–53 | Korean War1 |
| 1955 | Warsaw Pact is formed8 |
| 1957 | Soviet Union launches Sputnik 1, the first satellite11 |
| 1961 | Berlin Wall is built3 |
| 1962 | Cuban missile crisis1 |
| 1969 | Americans land on the Moon17 |
| 1979 | Soviet troops enter Afghanistan1 |
| 1985 | Gorbachev becomes Soviet leader4 |
| 1987 | Reagan and Gorbachev sign the INF Treaty7 |
| 1989 | Revolutions across Eastern Europe; the Berlin Wall opens (9 Nov)14 |
| 1990 | Germany reunites (3 Oct)20 |
| 1991 | Warsaw Pact ends (July); failed coup (Aug); Soviet Union dissolves (Dec)815 |
Mostly because of fear. Once both sides had nuclear weapons (the Soviets tested their first in 1949), a war between them could have destroyed both.1 Strategists called this mutual assured destruction: an attack by one would be met with a counterattack so large that attacker and defender would both be wiped out.10 The Cuban missile crisis of 1962 brought the superpowers to the brink, and showed that neither was ready to use nuclear weapons for fear of the other's response.1
So they competed in other ways, and proxy wars became the "acceptable" way to fight for influence.10 The Korean War (1950–53) and the Vietnam War were the biggest; the Soviet war in Afghanistan (from 1979) was another.1
| Year | United States | Soviet Union |
|---|---|---|
| 1956 (strategic warheads) | 2,123 | 84 |
| 1967 | more than 31,000 (US peak) | rising |
| about 1986 | falling | more than 40,000 (Soviet peak) |
US and Soviet figures from Britannica.9 Worldwide, the number of nuclear weapons peaked at roughly 70,300 in 1986. Most of the big cuts came in the 1990s, after the Cold War ended.18
On 4 October 1957 the Soviet Union launched Sputnik 1, the first artificial satellite. It shocked many Americans, who had assumed they were ahead, and started the space race.11 The race peaked on 20 July 1969, when American astronaut Neil Armstrong stepped onto the Moon.17
By the 1980s the Soviet economy was in deep trouble. It had drifted with low growth for years under Leonid Brezhnev (leader 1964–82).4 On top of that, the war in Afghanistan and a renewed arms race strained the budget, and by the early 1980s the government was quietly running large hidden deficits.13
In March 1985 the Communist Party chose Mikhail Gorbachev, then the youngest member of its ruling Politburo, as leader.4 His main goal was to revive the stagnant economy. When small changes didn't work, he tried two much bigger reforms:4
The reforms opened a door that was hard to close. Once people could speak freely, many asked for much more, including, in some Soviet republics, full independence.4
Gorbachev also wanted calmer relations with the West. In December 1987 he and Ronald Reagan signed the Intermediate-Range Nuclear Forces (INF) Treaty, the first arms-control deal to scrap an entire type of weapon: 2,619 missiles were dismantled over three years.7 In 1988–89 Soviet troops left Afghanistan.4
The biggest change was quieter. In the past, Soviet tanks had crushed protests in East Germany (1953), Hungary (1956) and Czechoslovakia (1968). Now Gorbachev made it clear, first secretly and then openly, that the Soviet Union would no longer use its army to keep communist governments in power.14 Then, in 1989, communist governments fell "like dominoes":14
In December 1989, US President George H. W. Bush and Gorbachev met at Malta; one of Gorbachev's staff later said they "buried the Cold War at the bottom of the Mediterranean."14 On 3 October 1990 East and West Germany became one country again,20 and Gorbachev even accepted the reunited Germany joining NATO.4 He won the Nobel Peace Prize that year.4
Inside the Soviet Union, the Baltic states and others demanded independence. In August 1991, hard-line Communists tried to seize power from Gorbachev. The coup failed within days, but it left him badly weakened and boosted Boris Yeltsin, the leader of Russia.15 Ukraine and Belarus declared independence days later. On 25 December 1991 Gorbachev resigned, and the Soviet flag was lowered over the Kremlin for the last time.15 The Soviet Union was replaced by 15 independent countries.6 The Warsaw Pact had already been declared "nonexistent" that July.8
The United States and its allies are usually called the winners: the Soviet Union disappeared and communist rule ended across Eastern Europe. But historians still argue about why it happened, and even about the exact date it ended.20 The main explanations are:
| Explanation | The argument |
|---|---|
| US pressure | Reagan's arms build-up and firm stand against communism pushed a strained Soviet economy past its limits. Britannica notes his policies "have been credited with contributing to the demise of Soviet communism."1213 |
| Gorbachev's choices | He chose reform, arms control and, above all, not to send in the tanks. Britannica calls him "the single most important initiator" of the changes of 1989–90.4 |
| A failing economy | Decades of slow growth, costly wars and the arms race left the Soviet system unable to keep up.413 |
| Ordinary people | Workers in Poland's Solidarity movement, marchers in East Germany and crowds in Prague took the risks that actually toppled their governments.14 |
Most historians combine these: the pressures built up over decades, and the choices made in the late 1980s decided how and when it ended. You can build your own answer with the cause tower in the last chapter of the explainer above.
Want to compare with another great power that came apart? See why the Roman Empire fell, a story that also had many causes instead of one.
There wasn't just one. The Soviet economy was failing, and the arms race and the war in Afghanistan made it worse. Mikhail Gorbachev's reforms (glasnost and perestroika) gave people the freedom to demand change, and he decided the Soviet army would no longer prop up communist governments in Eastern Europe. US pressure under Ronald Reagan and arms-control deals between the two leaders also mattered. Most historians say it took all of these together.
The United States and its allies are usually described as the winners, because the Soviet Union broke up in December 1991 and communist rule ended across Eastern Europe. But the end came mostly through reforms, treaties and peaceful protests, not a battle. Many historians also give credit to Gorbachev and to ordinary people in Eastern Europe.
Historians usually date it from about 1947, when the split between the Western allies and the Soviet Union hardened, to 1991, when the Soviet Union dissolved. Some mark the end at the fall of the Berlin Wall (9 November 1989) or the Malta summit between George H. W. Bush and Gorbachev (December 1989).
After World War II ended in 1945, the United States and Britain and the Soviet Union stopped trusting each other. The Soviets set up communist governments in the Eastern European countries their army had freed from the Nazis, while the US helped rebuild Western Europe. In 1946 Winston Churchill said an 'iron curtain' had come down across Europe, and by 1947–48 the continent was split into two camps.
Because the two superpowers, the US and the Soviet Union, never fought each other directly. The rivalry was 'cold': fought with arms races, the space race, propaganda and proxy wars, where each side backed opposite sides in someone else's war, as in Korea and Vietnam.
The United States and its allies (from 1949 organised as NATO) on one side, and the Soviet Union and its allies in Eastern Europe (from 1955 organised as the Warsaw Pact) on the other. Each side believed its system was better: democracy and free markets versus communist one-party rule and a state-run economy.
The Wall was the most visible symbol of a divided Europe. When East Germany opened its borders on 9 November 1989, it showed that the Soviet Union would not use force to keep Eastern Europe communist. Within months, communist governments across the region fell, Germany reunited in October 1990, and the Soviet Union itself broke up in December 1991.