• Capitalism (USA) vs Communism (USSR) — two totally opposed ideologies that were only allies "of convenience" during WWII
• The Grand Alliance broke down after Germany's defeat in 1945 — nothing left to hold the USA and USSR together
• Yalta (Feb 1945) went smoothly; Potsdam (Jul–Aug 1945) was tense — new leaders, the atomic bomb, and mistrust changed everything
• The atomic bomb (Hiroshima & Nagasaki, Aug 1945) terrified and angered Stalin, accelerating the arms race
• The Long Telegram (Kennan) and Novikov Telegram show both sides secretly believed the other wanted their destruction
• Churchill's "Iron Curtain" speech (March 1946) publicly declared the divide between East and West
• Stalin turned Eastern Europe into "satellite states" (Poland, Hungary, Romania, Bulgaria, Czechoslovakia, East Germany) as a buffer zone
• Truman Doctrine (1947) — the USA would help any country resist communism; ended US isolationism
• Marshall Plan (1947) — $13 billion in US economic aid to rebuild Western Europe and stop the appeal of communism
• The Berlin Blockade (1948–49) — Stalin's attempt to starve the West out of Berlin, defeated by the Berlin Airlift
• Consequences: NATO (1949), the Warsaw Pact (1955), and a permanently divided Germany (East/West)
• Orthodox historians blame Stalin; Revisionist historians blame the USA — there is no single "correct" answer

Here's the core problem in plain English: imagine two people who fundamentally disagree about how the world should be run — one believes everyone should own their own business and property (capitalism), the other believes the state should own everything so wealth is shared fairly (communism). Now imagine forcing them to be best friends and work together only because they have a mutual enemy trying to kill them both. That's the USA and USSR in World War II. The moment the enemy (Nazi Germany) was gone, there was no reason left for the friendship to survive.

Capitalism — the ideology where individuals can own property and businesses to make money. By 1941 the main capitalist powers were the USA (led by Franklin D. Roosevelt) and Britain. Roosevelt was fairly tolerant of Stalin and the USSR — he wanted to keep the peace.

Communism — the ideology where the state owns all property so everyone gets a fair share. By 1941 the USSR, led by Joseph Stalin, was the main communist power. Stalin's own domestic policies (forced collectivisation and rapid industrialisation) had already killed millions of his own people in the 1930s — which is exactly why the West was deeply suspicious of him even before the Cold War started.

This debate runs through the entire chapter, so get it clear now:

The Grand Alliance was made up of the USA, the USSR, and the UK, united to defeat the Axis powers of Germany and Japan. Even while working together, they were deeply suspicious of each other — the UK and USA were wary of communism and Soviet strength. Once the Axis powers were defeated by August 1945, the political map of the world shifted: the "old powers" like the UK and France declined in influence, while the USA and USSR emerged as the two new global "superpowers."

Held in Yalta (a city in the USSR) in the final months of WWII, while Roosevelt, Churchill and Stalin still needed each other to finish the war. This meeting went relatively smoothly.

What they agreed: Germany would pay $20 billion in reparations and be split into 4 zones; the USSR would fight Japan; the USSR agreed to free elections in Eastern Europe (this became the main area of disagreement later); Poland would hold free elections; the UN would be established.

Only a few months after Yalta, but everything had changed by the time the Big Three met again in Potsdam, Germany:

• Roosevelt had died — replaced by Harry S. Truman, who wanted a much tougher approach to Stalin
• Churchill lost the UK election — replaced by Clement Attlee
• Germany had now fully surrendered
• The USA had successfully tested the atomic bomb

This meeting was far more hostile. Stalin wanted harsher reparations from Germany; Truman wanted to protect the German economy instead. Truman was alarmed by Soviet control over Eastern Europe and believed Stalin was actively spreading communism. Stalin, meanwhile, wanted to keep his Red Army stationed in Eastern Europe as protection against future threats from the West.

In August 1945 the USA dropped two atomic bombs on Japan — the first on Hiroshima (6 August) and the second on Nagasaki (9 August). Roughly 120,000 Japanese civilians were killed.

Truman believed using the bomb would persuade Western Europe to support the USA, and encourage Eastern European countries to resist Soviet expansion and ally with America instead.

The atomic bomb increased Cold War tension because Truman wanted to flex American power to deter war and protect Eastern Europe from communism — but Stalin saw this as pure aggression, confirming his belief that the USA wanted to destroy communism, and making him willing to do whatever it took to protect the USSR, including tightening his grip on Eastern Europe.

George Kennan, the USA's ambassador in Moscow, sent an 8,000-word telegram back to Truman (hence the name — it was far longer than a normal telegram). His assessment: Stalin wanted to destroy capitalism because it threatened communism; the USA should aim to "contain" the USSR and communism; and peace would never be possible between the two nations. This telegram effectively became the intellectual foundation for the entire US policy of containment that followed.

The Soviet mirror image. Nikolai Novikov, the Soviet ambassador in Washington, sent his own report back to Stalin: the USA wanted to build up military strength to achieve world domination; after Roosevelt's death the USA no longer wanted to cooperate with the USSR; and the American public would support a war against the USSR.

Winston Churchill was no longer British Prime Minister, but was still hugely influential. In a speech delivered in the USA in March 1946, he declared:

The "Iron Curtain" referred to the impenetrable divide between capitalist countries in the West and communist countries in the East. Stalin believed the speech reflected the true beliefs of the US government (even though Churchill was no longer in office), and it increased tensions further — both sides built up their militaries, kicking off an arms race.

From 1943-45 the Soviet Red Army liberated much of Eastern Europe from Nazi control. After 1945, Stalin refused to leave — he wanted these countries to act as a buffer zone between the USSR and any future Western invasion. These countries became known as satellite states: they stayed in the "orbit" of the USSR, meaning they relied on the Soviet Union and had their politics and actions directly influenced by Moscow.

As each Eastern European country fell to communism, it confirmed Truman's fears about the spread of communism, heightened US anti-communist attitudes, and further encouraged the kind of thinking behind Churchill's Iron Curtain speech.

Greece and Turkey were struggling to hold off communist takeovers — Greece specifically was fighting a civil war between monarchists and communists. When Britain announced in 1947 it could no longer afford to militarily support the Greek government, Truman decided America had to step in.

On 12 March 1947 Truman announced the USA would send $400 million to Greece and Turkey. In his speech, he described nations as having two alternative "ways of life":

General George Marshall visited Europe and reported back to Truman that almost every country in Europe was at risk of turning to communism — WWII had caused massive destruction, and many desperate people saw communism as an appealing way to redistribute wealth and rebuild their lives. Marshall's solution: provide these countries with economic aid so they wouldn't feel forced to turn to communism.

The US Congress passed the Marshall Plan after Czechoslovakia became communist in 1948 — that event was the final push needed to get it approved. In total, the Marshall Plan gave $13 billion to 16 Western European countries (on top of $12.7 billion already given before the plan). The amount each country received was based on its population and pre-war economy. British Foreign Secretary Ernest Bevin called it a "lifeline to sinking men."

The Marshall Plan was technically offered to the Eastern European satellite states too — but Truman knew perfectly well that Stalin would never allow them to accept American money.

Stalin saw the Truman Doctrine and Marshall Plan as a direct threat to communism and the USSR, and accused them of taking over a role that should belong to the United Nations. He called the Marshall Plan "dollar imperialism" — arguing the USA was simply using money to expand its own empire and push free-market capitalism and democracy onto Europe.

The result: the Marshall Plan permanently divided the West from the East. Satellite states supported the USSR; recipients of Marshall Aid supported the USA. Together, the Truman Doctrine and Marshall Plan significantly increased Cold War tensions.

At Potsdam, Berlin (like Germany itself) was split into zones — the USA, Britain and France controlled the western zones, the USSR controlled the eastern zone. Even though Berlin sat physically deep inside Soviet-controlled East Germany, it was jointly run.

Stalin believed the West had no right to be in Berlin at all, since it fell within East Germany. Trizonia's new currency (the Deutschmark) threatened Soviet power in Germany — it split Berlin into two economic zones, and since capitalist Trizonia had a much stronger economy, this would make the USSR look weak in comparison.

By 1948 Stalin had decided that blockading Berlin — cutting all road, rail and canal links — would starve the West out of the city entirely.

West Berlin only had enough food for 36 days and lacked fuel and medicine. The West faced a genuine trap: fight to break the blockade and risk war, or do nothing and simply hand Berlin over to the USSR.

The West chose the air route — a genuinely clever tactic, because it wasn't an aggressive action, and the USSR would clearly be starting a war if it shot down the planes.

• The USA and Britain flew in around 1,000 tons of supplies every single day
• By January 1949, 170,000 tons of supplies were being sent into Berlin in a single month
• At Berlin-Tempelhof airport, a plane landed roughly every 45 seconds at the height of the airlift
• At least 78 people died in aircraft accidents — but the Soviet military caused no casualties, because they never shot a single plane down
• Stalin offered to let West Berliners move to East Berlin to receive food — most refused
• The Allies refused Stalin's offer to lift the blockade in exchange for removing the Deutschmark from West Berlin

The blockade badly damaged Stalin's position. He couldn't stop the airlift — shooting down planes carrying supplies would mean starting a war he wasn't ready for — and simply doing nothing while the West succeeded made the USSR look weak and humiliated. On 12 May 1949, Stalin lifted the Berlin Blockade (the West kept flying supplies until 30 September, just to be safe). It was a huge propaganda victory for the West.

Several major consequences followed directly from the crisis:

This is the essay-style question this whole chapter builds towards. There's no single "correct" answer — historians genuinely still disagree, and the Cambridge IGCSE wants to see you weigh up evidence on both sides and reach your own supported judgement.

• I can explain the difference between capitalism and communism as ideologies
• I understand why the Grand Alliance was only a "marriage of convenience"
• I can compare the outcomes of Yalta and Potsdam and explain why Potsdam was more difficult
• I can explain why the USA used the atomic bombs on Japan (official and unofficial reasons)
• I understand how the atomic bomb damaged the US-Soviet alliance
• I can explain the content and impact of the Long Telegram and Novikov Telegram
• I understand what the "Iron Curtain" speech meant and why it mattered
• I can describe how the USSR took control of at least three Eastern European countries
• I can explain the Truman Doctrine and the shift from isolationism to containment
• I understand the purpose and impact of the Marshall Plan
• I can explain why Stalin started the Berlin Blockade
• I understand why the West chose to respond with an airlift rather than by land
• I can list the consequences of the Berlin Crisis (NATO, Warsaw Pact, divided Germany)
• I can present both the Orthodox and Revisionist arguments on who was to blame
• I can write a balanced essay conclusion using "fully" or "partially" to weigh blame