Key Idea: After beating Hitler together in 1945, the USA and USSR fell out fast because their beliefs were opposite: capitalism and democracy versus communism and one-party rule. That clash hardened into the Cold War — a 45-year rivalry of blocs, alliances and a nuclear arms race that finally ended when the USSR reformed and collapsed in 1991.
🤝 17.1.1 — From allies to rivals
In the Second World War the USA, USSR and Britain teamed up against Nazi Germany. Historians call this the Grand Alliance — but it was a marriage of convenience (a partnership built on need, not trust), and once Hitler was beaten in 1945 the glue was gone.
The two sides saw the world in opposite ways. The USA wanted democracy (free elections) and capitalism (private business, market prices); the USSR wanted a one-party state and communism (the state owns everything, a planned economy). Wartime events deepened the distrust — the delayed Second Front (the West took years to invade Western Europe while Soviets did most of the dying), the US atomic bomb, and Stalin's buffer zone of friendly states in Eastern Europe, which he saw as defence but the West saw as aggression.
Two summits show the friendship cooling. Yalta (February 1945) was still warm — the Big Three agreed a new United Nations, splitting Germany into four zones, and 'free elections'. Potsdam (July–August 1945) was tense: Roosevelt had died (replaced by Truman) and they clashed over Poland and reparations. By 1946 Churchill's 'Iron Curtain' speech declared Europe split in two.
- Grand Alliance — the WWII partnership of USA, USSR and Britain against Nazi Germany; a marriage of convenience, not real trust
- Capitalism vs communism — private ownership + market economy versus state ownership + command (planned) economy
- Buffer zone — the belt of friendly states Stalin wanted in Eastern Europe to protect the USSR from future attack
- Yalta (Feb 1945) — cooperative: UN, four German zones, free elections promised, USSR to fight Japan
- Potsdam (Jul–Aug 1945) — tense: clashes over Poland and reparations; Truman tougher after the atomic bomb test; 1946 = Churchill's 'Iron Curtain' speech
🛡️ 17.1.2 — Containment and the division of Europe
By 1947 the USA decided it would no longer just watch communism spread — it would contain it (stop it spreading further, without rolling it back where it already existed). This came in two arms. The Truman Doctrine (March 1947) promised to support 'free peoples' against takeover, sending about $400 million to Greece and Turkey. The Marshall Plan (1947–48) poured roughly $13 billion into rebuilding Western Europe, because Americans feared poverty was what communism fed on.
Stalin called it 'dollar imperialism' and hit back with Cominform (1947) and Comecon (1949). The sharpest clash came over Germany: when the West merged its zones and launched a new currency, Stalin cut off West Berlin in the Berlin Blockade (June 1948–May 1949). The West beat it with the Berlin Airlift, flying in supplies for almost a year until Stalin backed down. Europe then locked into two armed camps — NATO (1949) versus the Warsaw Pact (1955) — with two Germanys, the FRG (West) and GDR (East), both created in 1949.
- Containment — the US strategy of stopping communism spreading further (not reversing it)
- Truman Doctrine (Mar 1947) — the political promise: ~$400m aid to Greece and Turkey; 'free vs totalitarian' framing
- Marshall Plan (1947–48) — the economic engine: ~$13bn to rebuild Western Europe and starve communism of recruits
- Berlin Blockade (Jun 1948–May 1949) — Stalin cut off West Berlin; defeated by the Airlift
- Action–reaction pattern — Marshall Plan → Comecon; NATO 1949 → Warsaw Pact 1955; FRG & GDR both 1949
☢️ 17.1.3 — Arms race, détente and the end of the Cold War
After 1945 the USA held the only atomic bomb — until the USSR tested its own in 1949, and both built the far deadlier hydrogen bomb (USA 1952, USSR 1953). By the 1960s each side could destroy the other even after being hit first — a grim balance called Mutually Assured Destruction (MAD). Because attacking meant your own certain death, neither ever pressed the button, which may be why the Cold War stayed 'cold'.
In the 1970s tension eased in détente (a relaxing of hostility): SALT I (1972) limited missiles, and the Helsinki Accords (1975) accepted Europe's borders. But the Soviet invasion of Afghanistan (1979) shattered trust, and President Reagan (calling the USSR an 'Evil Empire' in 1983) reopened a Second Cold War. The turning point was Mikhail Gorbachev (from 1985), whose reforms — glasnost ('openness') and perestroika ('restructuring') — plus the INF Treaty (1987) and his refusal to send in troops, unleashed the peaceful 1989 revolutions and the collapse of the USSR in 1991.
- Arms race — US monopoly (1945–49), Soviet A-bomb (1949), H-bomb (USA 1952 / USSR 1953)
- MAD — both sides destroyed in any nuclear war, so neither dares strike first — helped keep the peace
- Détente (1970s) — SALT I (1972) limits missiles; Helsinki Accords (1975) accept borders
- Second Cold War — Soviet invasion of Afghanistan (1979); Reagan's build-up and 'Evil Empire' (1983)
- Gorbachev (1985–91) — glasnost, perestroika, INF Treaty (1987), the 1989 revolutions, USSR collapse (1991)
✍️ Exam-ready answers
Examine the reasons why the wartime Grand Alliance had broken down by 1946.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
To what extent was the Soviet Union responsible for the division of Europe by 1955?
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
🎯 One-glance recall
Why the alliance broke (1945–46) Opposite beliefs (capitalism vs communism) plus wartime mistrust (late Second Front, the atomic bomb, the buffer zone). Yalta (Feb 1945) was warm; Potsdam (Jul–Aug 1945) was tense; by 1946 the 'Iron Curtain' had cut Europe in two.
Containment and the two blocs The Truman Doctrine (Mar 1947) and Marshall Plan (1947–48) contained communism. Stalin replied with Cominform/Comecon and the Berlin Blockade (1948–49), beaten by the Airlift. Europe split into NATO (1949) vs Warsaw Pact (1955), and the FRG vs GDR (1949).
Arms race and MAD US monopoly (1945–49) ended when the USSR got the bomb in 1949; both then built H-bombs (1952–53). MAD meant a direct war would destroy both sides, so the rivalry was fought everywhere except head-on.
How it ended (1970s–1991) Détente (SALT I 1972, Helsinki 1975) eased tension; Afghanistan (1979) and Reagan reopened a Second Cold War. Gorbachev's glasnost, perestroika, the INF Treaty (1987) and non-intervention brought the 1989 revolutions and the USSR's collapse in 1991.