The Tehran Conference was held in November 1943 at the Russian Embassy in Tehran. It was to discuss the strategy to win the war and in particular the opening of a 'Second Front' in Western Europe.

The 'Second Front' opened with the Allied invasion of Normandy on 6 June ('D-Day'). This followed the surrender of German forces in Italy on 2 May 1944. Stalin thought that the Normandy Invasion had been delayed in order to weaken the USSR and this was a source of tension between the Allies.

The Yalta Conference was thought to be a success at the time, with some areas of agreement. However, there were tensions under the surface. One dispute was the position of the Western border of Poland. Stalin wanted to move the Polish border to the Rivers Oder and Neisse,  the 'Oder-Neisse Line'. Churchill and Roosevelt refused to agree.

This conference was much less successful. Truman told Churchill about the atom bomb but not Stalin. Stalin had gone ahead and occupied the area to the Oder-Neisse Line, expelling 5 million Germans.

The counting of the votes for the July election did not start until 26 July because so many votes had to be brought from servicemen overseas. Stalin was bemused that the war leader Churchill, whom he respected, could be so easily removed from power! Stalin was less impressed by the quietly spoken Attlee.

We now know that Stalin's spies had infiltrated the top secret 'Manhattan Project' and so had probably kept Stalin informed of the progress of the atom bomb. This shows that even when they were fighting the war together, the allies were still spying on each other!

The first atom bomb was followed by a second one on Nagasaki on 9th August and the war with Japan came to an end on 10th August. This meant that the Americans defeated Japan without Russian aid and so Russia was allowed no part in the occupation of Japan.

The USSR army stayed as an army of occupation in the Eastern European states they had liberated from the Germans. The Eastern zone of Germany, Poland, Hungary, Czechoslovakia, Rumania, and Bulgaria. By contrast, the American troops returned home as quickly as they could in 1945. This created an inbalance of power, temporarily.

The force of the Red Army was used to impose Communist regimes. Elections were held in some cases, for example Hungary. The Communists won 20% of the vote but the government was made up of a majority of Communists. Czechoslovaka was the most westerly of these states and elected a coalition government in 1946, which included non-Communists.

He spoke at a High School in Fulton, Missouri, which was significant because it was Truman's home state and Truman invited him. Truman was seated on the platform behind him. The speech was a direct attack on the Soviets. In calling for a western alliance against the threat of Communism this speech divided the wartime allies.

There is some truth in all of these answers perhaps, but the 'Long Telegram' is seen as decisive. George Kennan was a diplomat based in Moscow. He had been asked to report on Soviet intentions in Europe and he concluded that The USSR would continue to be expansionist and aggressive and would only respond to 'the logic of force'.

The purpose of the Cominform was to unite European communist parties. All the Russian sattelite states in Eastern Europe were members and were to be turned into states like Russia, with industrialisation and collectivisation of agriculture, and central control.

This was the 'coup' by which the Soviets took control of Czechoslovakia. Masaryk was a leading non-Communist member of the government. His murder echoed the 'defenestration of Prague' which triggered the Thirty Years' War in 1618. At the May election voters were presented with a list of only communists to vote for.

The division of Germany into zones of occupation was meant to be temporary, but in the years to 1948 the two parts of the country, western zones and eastern zones, developed very differently. Stalin refused to cooperate in the recovery of Germany and made it impossible for the zones to be jointly administered. 

The Truman Doctrine was a response to the Greek Civil War. Britain had helped to restore the monarchy in Greece after the war but this was now threatened by a communist uprisng which was supported by neighbouring communist states. Bevin, the British foreign minister, wrote to Truman to ask for help. America sent aid and the communists were defeated by 1949.

Molotov, the Russian foreign minister denounced this aid as 'dollar imperialism'. Czechoslovakia was interested in accepting it, before the coup of 1948. Of course the USA wanted to bind the countries more closely to themselves and to support capitalism. Marshall Aid was the economic extension of the Truman Doctrine.

Supported by Marshall Aid, the new currency was introduced to West Berlin and rationing was ended. The Soviets were annoyed by the prosperity of the capitalist West Berlin in the the middle of the communist zone. The new currency was the last straw. (NATO was a consequence of the Berlin Blockade.)

The population of Berlin included many refugees. The supplies needed for the winter included coal for heating and electric power generation, medical supplies as well as food. Stalin had calculated that there was no way that the people could be supplied by air and that they would have to turn to the communists for help, so ending the Western occupation of Berlin.

General Clay was convinced that the Communists had to be stopped from expanding, he feared that communism would become 'rampant' in Europe. It was President Truman who said 'we stay'. The comment about Siberia was made by West Berliners, explaining why they could put up with the hardship.

The policy of containment developed from 1946 with the recognition that the Soviet expansion in Europe must be met by force. The west did not feel powerful enough to drive the Soviets back, but believed they must stop any further expansion. The 'Cold War' had begun and the political map of Europe became fixed. Cold War rivalries then moved to other parts of the world, especially Asia.