All of Eastern Europe.
When the Soviets marched through eastern Europe they occupied it and therefore it was communist.
Europeans did not favor communism after world war 2. Communism was forced on the people of Eastern Europe by thd Soviets.
The Eastern Front of World War Two was in the Soviet Union and Eastern Europe.
The Soviet Union's aggression after World War II was especially focused in Eastern Europe. Winston Churchill claimed the Soviet Union was extending the Iron Curtain.
Stalin Refused to allow free elections in eastern Europe World War 2
Most of Eastern Europe was occupied by Soviet Russia after the Second World War. They then set up puppet governments in those countries. (You can argue about if the Soviets in the 1940's-1990's were actually Communists or not else where)
russia
The western allies on the western front, and the Soviets on the Russian Front.
For a few years after World War 2, the Americans had nuclear weapons, and the Soviets did not. It was agreed before the war ended that the Soviets would administer Eastern Europe, and it was hoped that these countries would be given their freedom, but the Soviet acquirement of the nuclear secret changed everything.
Communism
USSR .