Why did the Soviets occupy Eastern Europe at the end of World War II?
At the end of World War II, the Soviet Union occupied the countries of Eastern Europe. They had reasons for wanting to have influence over these countries.
The Soviet Union knew they were going to have conflicts with the United States and with Great Britain over the spread of communism. The Soviet Union wanted to spread communism throughout the world, and they were prepared to do that, even if it meant breaking agreements they had made with the United States and with Great Britain. As a result, the Soviet Union viewed the Eastern European countries as a buffer against any possible attack by the noncommunist world. The Soviet Union understood the Eastern European countries could serve as a form of protection if a war occurred in the future.
The Soviet Union took actions to be sure that Eastern Europe was communist. For example, the Soviet Union pressured the King of Romania into having a communist government, even though it violated the Declaration of Liberated Europe. The Soviet Union also didn’t hold free elections in Poland to include some members of the pre-war Polish government in the post-war Polish government. The Soviet Union was determined to have a buffer against a potential attack by the noncommunist world. They also were determined to spread communism wherever they could do that.
After being surprised by an all-out attack by Germany in 1941 that exacted a vast toll in terms of Russian lives lost and devastation rendered, the Soviets were determined to put a well-fortified buffer between themselves and capitalist western European states after the war. Therefore, under the direction of Stalin, the USSR moved relentlessly to bring the Eastern European nations under its sphere of influence into what was called the Warsaw Pact, a group of nations not a part of NATO, and to ensure that these countries installed socialist governments sympathetic to Soviet aims.
While Stalin moved ruthlessly to establish dominance in Eastern Europe after World War II, these plans were also part of his pre-war goal to spread communism farther in Europe. From the 1920s, Stalin had seen the USSR as an "island" of communism "encircled" by capitalist countries and hence vulnerable to attack: he wanted very much to change that balance of power to ensure the survival of his state and to turn the tables on the west so that it would feel vulnerable. Being part of the winning side in World War II gave him his opportunity to do so.