Cold War

1945: February 4-11-- Yalta Conference Cold War Begins

1945: August 6 -- United States first used atomic bomb in war

1945: August 8 -- Russia enters war against Japan

1945: August 14 -- Japanese surrender End of World War II

1946: Potsdom Conference Stalin refusing to pull out of Iran

1946: March -- Winston Churchill delivers "Iron Curtain" Speech

1947: March -- Truman Doctrine announed. Truman declares active role in Greek Civil War

1947: June -- Marshall Plan is announced

1948: February -- Communist takeover in Czechoslovakia

1948: June 24 -- Berlin Blockade begins

1949: July -- NATO ratified

1949: May 12 -- Berlin Blockade ends

1949: September -- Soviets explode first atomic bomb

The Big Three further agreed that democracies would be established, all liberated European and former Axis satellite countries would hold free elections and that order would be restored. The Western Powers soon realized that Stalin would not honor his free elections promise regarding Poland.

Is that expansionist?

Soviet was willing to compromise on the promises it made to maintain influence in Poland. This could be seen as expansionist. However, it can also be seen as a defense tactic as Poland could act as a 'buffer state'

Entering Iran was something both the UK and Russia did together, as a preventive measure against Germany. So that initial takeover cannot be seen as expansionist. However, the delay in Russia pulling out can be seen as so. But the fact that they did leave in 1946 shows that they Russia had no intention of establishing a long-lasting communist influence on Iran.

The Truman Doctrine can be seen by some as the start of the Cold War. This is because:

US was implying an unprecedented commitment to resist communism throughout the world. Policy of containment made the divide even clearer. So as to justify Soviet policies that were in reaction to this and the Marshall Plan: Comecon and Comintern.

Communist Party of Czech with Soviet backing, assumed undisputed control over the government of Czechoslovakia. 

This can be seen as expansionist.

By the Americans, this was seen as an expansionist policy by Russia. Why? Because they thought they'd use this to take over West Berlin. However, to the Soviets it was just a reaction to the newly introduced Deutchmark in Germany, a new currency, by the West. 

Soviet policy: Took over most of Eastern Europe. Although this can be seen as expansionist, it wasn't really. Soviet was taking over Eastern Europe to make a buffer zone. This prevented direct military intervention by a foreign nation. Soviet was devastated after the second world war, and had been attacked twice in that century alone. Allowed it to fear another attack and thereby protect itself.