Long-Term Rivalry

The Soviet Union and the West were allies during the Second World War, but they had not been natural friends before it. Their wartime partnership was a practical alliance against Nazi Germany, not a deep agreement about politics, economics or the future of Europe.

The long-term rivalry began with the Russian Revolution of 1917. The Bolsheviks created the world's first communist state. Many Western governments feared that communist revolution might spread beyond Russia, threaten private property and weaken capitalist societies. Soviet leaders, in turn, remembered Western hostility to Bolshevik rule and saw capitalist countries as potential enemies.

By the 1930s and 1940s, the ideological contrast was sharp:

This mattered because ideology shaped how each side interpreted the same events. If the Soviet Union supported communists in Eastern Europe, Stalin could present it as protection for socialism and security after German invasion. Western leaders could see the same action as aggressive expansion. If the USA promoted trade, markets and elections, Western leaders could present it as freedom and recovery. Stalin could see the same policy as capitalism trying to surround and weaken the USSR.

The Second World War did not remove these suspicions. It temporarily pushed them into the background.

Wartime Strain

The wartime alliance began because Hitler made it necessary. Germany invaded the Soviet Union on 22 June 1941. The United States entered the war after the Japanese attack on Pearl Harbor in December 1941. From then on, Britain, the USA and the USSR had a shared enemy.

There was real cooperation. The Soviet Union carried the heaviest fighting against Germany on the Eastern Front. Britain and the USA supplied aid and eventually opened a western front in France. Without that cooperation, defeating Nazi Germany would have been far harder.

But cooperation sat beside mistrust. Three tensions were especially important.

First, Stalin was angry about the delay in opening a second front in Western Europe. The USSR wanted Britain and the USA to invade France as soon as possible to relieve pressure on the Eastern Front. The Western Allies did not launch D-Day until 6 June 1944. Stalin saw the delay as evidence that the West was willing to let the Soviet Union bleed.

Second, Poland caused deep disagreement. Poland lay between Germany and the Soviet Union, so Stalin wanted control or at least a friendly government there for security. Britain had gone to war in 1939 after Germany invaded Poland, so Western leaders could not easily ignore Polish independence. Poland therefore became both a strategic issue and a moral issue.

Third, secret diplomacy and military secrecy damaged trust. British and American leaders sometimes excluded Soviet representatives from sensitive negotiations. The Manhattan Project, which produced the atomic bomb, was also kept secret from Stalin during most of the war. Even when the alliance was still functioning, each side was already preparing for a postwar world in which the other might become a rival.

A useful way to think about this part is: the alliance solved the immediate problem of defeating Hitler, but it did not solve the deeper problem of what Europe should look like after Hitler.

Tehran To Yalta

The wartime conferences tried to turn military cooperation into postwar planning. They also exposed how differently the leaders imagined the future.

At Tehran, from 28 November to 1 December 1943, Roosevelt, Churchill and Stalin met together for the first time. The most important military decision was the Western commitment to Operation Overlord, the invasion of northern France, in 1944. Stalin agreed that Soviet forces would launch pressure on the Eastern Front to help. This reduced one major wartime complaint, although the delay had already left bitterness.

Tehran also raised postwar questions. The leaders discussed Poland's borders and the future of Eastern Europe. Stalin wanted the Soviet border with Poland pushed westwards. This was not just a map issue. For Stalin, moving borders and shaping governments were ways to create security after repeated invasions through Eastern Europe. For Britain and the USA, these moves raised the question of whether smaller countries would be free after liberation.

At Yalta, from 4 to 11 February 1945, Germany was close to defeat. Roosevelt, Churchill and Stalin made several important agreements:

Yalta looked like a success at the time because the leaders reached agreements. The problem was that some agreements were vague. The West thought "free elections" meant genuine political choice. Stalin thought a "friendly" Eastern Europe was essential to Soviet security, and he did not trust anti-communist governments on his borders.

That ambiguity was a cause of the Cold War because it allowed each side to accuse the other of bad faith. Western leaders could say Stalin broke the spirit of Yalta by dominating Eastern Europe. Stalin could say he was protecting Soviet security in the zone the Red Army had liberated.

Potsdam

Potsdam, from 17 July to 2 August 1945, was different from Tehran and Yalta because the war in Europe was over. Germany had surrendered on 8 May 1945. Once the common enemy in Europe had gone, the Allies had less reason to hide their disagreements.

The people at the table had also changed. Roosevelt had died in April 1945, so Harry S. Truman represented the USA. Churchill began the conference for Britain but was replaced by Clement Attlee after the British election result. Stalin remained the Soviet leader. This meant Stalin was the most experienced of the three main leaders at Potsdam, while Truman was still learning the details of high-level diplomacy.

Potsdam produced agreements about Germany:

These agreements did not remove suspicion. Stalin wanted Germany weakened and wanted large reparations because the Soviet Union had suffered enormous destruction. Truman and his advisers wanted to avoid punishing Germany so harshly that it became unstable again, as many believed had happened after the Treaty of Versailles.

The atomic bomb also affected the mood at Potsdam. The USA successfully tested an atomic bomb on 16 July 1945. Truman told Stalin during the conference that the USA had a powerful new weapon. Stalin already knew about the bomb through Soviet intelligence, but the episode still mattered. It showed that the USA had a new source of power and that major wartime secrets had been kept between supposed allies.

Potsdam therefore turned wartime suspicion into visible postwar disagreement. The leaders could agree on broad principles, but the practical questions - Germany, reparations, Poland, borders and power in Europe - showed that cooperation was becoming harder.

Eastern Europe

Eastern Europe was central to the reasons for the Cold War because it linked ideology, security and power.

From Stalin's point of view, Soviet control or influence in Eastern Europe could be presented as defensive. Germany had invaded Russia in the First World War and the Soviet Union in the Second World War. The Nazi invasion had caused catastrophic Soviet losses. Stalin wanted a buffer zone of friendly states between Germany and the USSR, especially in Poland, Romania, Bulgaria, Hungary and other countries reached by the Red Army.

From the Western point of view, the same policy looked aggressive. If "friendly" governments meant communist-dominated governments controlled by Moscow, then the promise of free elections had little meaning. Western leaders feared that Soviet control in Eastern Europe would not stop with security. It might become permanent domination and the spread of communism.

This is why Eastern Europe was so explosive:

For this row, the key point is not every later step of Soviet expansion. That comes next in the course. The key point here is causation: Eastern Europe became the place where old mistrust turned into a direct clash over borders, governments and ideology.

This also explains why both sides could claim they were acting defensively. Stalin could say he was preventing another invasion. Truman and Western leaders could say they were defending free countries from Soviet control. A Cold War became more likely when each side saw its own actions as protection and the other side's actions as aggression.

Truman And Stalin

Personal attitudes did not cause the Cold War on their own, but they made the existing causes sharper.

Roosevelt had believed that he could work with Stalin if the USA recognised some Soviet security concerns and brought the USSR into international cooperation through the United Nations. Truman was more suspicious. When he became president in April 1945, he inherited a complicated situation: Yalta promises were already disputed, the Red Army was already across Eastern Europe, Germany had to be controlled, and the USA was close to having an atomic bomb.

At first Truman still hoped he could deal with Stalin. During Potsdam, he even felt some confidence after meeting him. But his attitude hardened as disagreements over Poland, Germany and Soviet behaviour grew. Truman came to see firmness as necessary. That mattered because a leader who expects cooperation will interpret problems differently from a leader who expects confrontation.

Stalin's attitude was also shaped by deep suspicion. He led a one-party communist state and distrusted capitalist powers. The delayed second front, Western secrecy and the atomic bomb all fitted his belief that the West might try to weaken the Soviet Union. At the same time, Stalin was not simply reacting. He used the Red Army's position in Eastern Europe to build Soviet influence and reduce the chance of anti-Soviet governments near his borders.

You can organise the causes like this:

A strong exam judgement avoids blaming everything on one person. It weighs the causes. For example:

The most important reason for the Cold War was the clash over Eastern Europe because it turned ideological suspicion into a practical dispute about who would control governments and borders after 1945. However, this clash was made worse by long-term rivalry between communism and capitalism and by wartime tensions such as the delayed second front. Truman and Stalin mattered because their attitudes made compromise harder, but those attitudes were powerful because they were attached to real disagreements over security, ideology and postwar Europe.

Misconception check: the Cold War was not inevitable in a simple, automatic way. The Allies did cooperate against Hitler and did reach agreements at Tehran, Yalta and Potsdam. But each agreement carried unresolved questions. By 1945, those unresolved questions were serious enough that the alliance began to unravel.