Allies against Hitler

The story begins not with hostility but with alliance. In 1941 both powers were drawn into the Second World War: the USSR when Germany invaded it in June 1941, and the USA after the attack on Pearl Harbor in December 1941.

• They shared one great enemy — Nazi Germany — and fought as members of the Grand Alliance alongside Britain.
• But their ideologies were opposite: the USA stood for capitalism and democracy; the USSR for communism and a one-party state.
• The alliance was one of necessity, not friendship — and it would not survive the peace.

Misconception alert: the USA and USSR were allies from 1941 to 1945. The Cold War grew out of a broken alliance, not out of two enemies who had always hated each other.

Yalta and Potsdam

As victory neared, the "Big Three" leaders met to plan the post-war world — and the cracks in the alliance began to show.

• Tehran (1943) and then Yalta (February 1945) — Roosevelt, Churchill and Stalin agreed to divide Germany into zones, hold free elections in Eastern Europe, and set up the United Nations.
• Potsdam (July 1945) — Truman was now US president. Tensions were clear over Poland, reparations, and the atomic bomb the USA had just tested.

Why it mattered: between Yalta and Potsdam, trust collapsed. A new, tougher US president and disagreements over Eastern Europe turned wartime partners into suspicious rivals.

Friends first?

The atomic bomb and distrust

In August 1945 the USA dropped atomic bombs on Hiroshima and Nagasaki, ending the war with Japan. It also sent a signal about American power.

• Stalin was deeply suspicious that the USA had kept the bomb secret and now held a huge advantage.
• The USSR raced to catch up and tested its own atomic bomb in 1949 — the start of the nuclear arms race.

Key idea: nuclear weapons made the rivalry terrifyingly dangerous — but they also made both sides cautious, because a direct war could destroy everyone.

The Cold War takes shape

Between 1946 and the mid-1950s, Europe split in two and the two sides built rival alliances:

• Churchill's "Iron Curtain" speech (1946) described a divided Europe.
• The Truman Doctrine and Marshall Plan (1947) set out the US policy of containment — stopping the spread of communism, partly through economic aid.
• The Berlin Blockade and Airlift (1948–49) — Stalin cut off West Berlin; the West flew in supplies until he backed down.
• NATO was formed in 1949; the communist Warsaw Pact followed in 1955.

Continuity: the "Cold War" was a war of ideology, threats and rival blocs — not a direct US–USSR shooting war. That is exactly why it was called "cold".

Name the year

Crises and the edge of war

The Cold War produced repeated crises, especially over Europe and the Soviet grip on the East:

• The Hungarian Uprising (1956) was crushed by Soviet tanks.
• The Berlin Wall was built in 1961 to stop people fleeing communist East Berlin.
• The Prague Spring in Czechoslovakia was crushed in 1968, and the Brezhnev Doctrine asserted the USSR's right to intervene in its satellite states.

Pattern to notice: again and again the USSR used force to keep control of Eastern Europe, while the USA protested but did not risk direct war over it.

The Cuban Missile Crisis

In October 1962 the world came the closest it ever did to nuclear war. The USSR had placed nuclear missiles on Cuba, within striking distance of the USA.

• Kennedy and Khrushchev faced off during a tense 13-day standoff, with US ships blockading the island.
• The crisis was resolved by negotiation: the USSR removed its missiles from Cuba; in return the USA promised not to invade Cuba and secretly agreed to remove its own missiles from Turkey.

Why it matters: the crisis showed how a Cold War flashpoint could nearly cause disaster — but also that both sides ultimately chose to step back.

Thirteen days in 1962

Détente, then renewed tension

After the terror of 1962, the 1970s brought an easing of tension known as détente:

• SALT I (1972) limited some nuclear weapons; the Helsinki Accords (1975) improved cooperation and recognised Europe's borders.
• But the Soviet invasion of Afghanistan (1979) shattered détente and began a "Second Cold War".
• US President Reagan took a tougher line and announced SDI ("Star Wars", 1983), a plan for a space-based missile defence.

Change and continuity: relations were not a straight line. They warmed during détente, then chilled again — before the biggest change of all in the later 1980s.

The end of détente

What did each one mean?

Tap an event or figure on the left, then tap its significance on the right.

Gorbachev changes everything

In 1985, Mikhail Gorbachev became Soviet leader. His reforms transformed the Cold War:

• Glasnost ("openness") and perestroika ("restructuring") tried to modernise a struggling USSR.
• He signed the INF Treaty (1987) with Reagan, scrapping a whole class of nuclear missiles.
• Crucially, he abandoned the Brezhnev Doctrine — the USSR would no longer use force to prop up communist governments in Eastern Europe.

Turning point: once Moscow would not send in the tanks, the peoples of Eastern Europe were free to push for change — and they did.

The Wall falls, the USSR dissolves

In 1989, mostly peaceful revolutions swept across Eastern Europe, and on 9 November 1989 the Berlin Wall fell — the great symbol of a divided Europe came down.

• Germany was reunified in 1990.
• The USSR was formally dissolved in December 1991 — and with it, the Cold War came to an end.

Misconception alert: the Cold War ended largely peacefully, through the collapse of the USSR — not through a war between the superpowers.

Gorbachev's reforms

A new world order

With the USSR gone, the USA was left as the world's only superpower — a "unipolar" moment. But the end of one rivalry did not bring lasting peace:

• New conflicts emerged, such as the Gulf War (1991).
• The 9/11 attacks (11 September 2001) triggered the "War on Terror", including the wars in Afghanistan (from 2001) and Iraq (from 2003).
• Relations between the West and a resurgent Russia grew more complicated through the 2000s.

The big shift over time: from a two-superpower Cold War to a US-dominated then increasingly complex, multi-sided world by 2010.

Timeline: 1941 → 2010

Put the events in order

Tap the events in the correct time order, from earliest to latest.

Why relations changed

OCR wants you to explain why superpower relations changed (or stayed tense) across the period. Look for these recurring factors:

• Ideology — capitalism/democracy vs communism drove suspicion on both sides.
• Nuclear weapons — the arms race made war unthinkable, forcing caution and, later, arms-control talks.
• Individual leaders — Truman, Kennedy & Khrushchev, Reagan & above all Gorbachev.
• Crises & the economy — Berlin, Cuba and Afghanistan shifted the mood; a struggling Soviet economy pushed Gorbachev to reform.

Turning points to argue for: the Cuban Missile Crisis (1962) (the brink of war, then a step back) and Gorbachev's leadership from 1985 (which led to the Cold War's peaceful end) are the two strongest "biggest turning point" answers.

Why "cold"?

Using sources on the Cold War

You will handle sources — speeches, cartoons, photographs, posters — about superpower relations. Two habits win marks:

• Ask who made it and why (provenance). A Soviet poster and an American cartoon each push their own side's viewpoint — propaganda was a Cold War weapon.
• Use your own knowledge to judge it. Support or challenge a source with facts you know about the period.

Interpretations differ: historians disagree about who was more to blame for the Cold War, and about why it ended — was it Gorbachev's reforms, Reagan's pressure, or Soviet economic weakness? Being aware that interpretations vary is exactly what the exam rewards.

Name the leader

The Wall comes down

The essentials to remember

You've covered the whole OCR Superpower Relations 1941–2010 study. Press Finish to see your score.