Why did the Soviet union set up communist states in the eastern Europe?

The Soviet Union established communist states in Eastern Europe primarily to create a buffer zone against potential Western aggression following World War II. By installing pro-Soviet regimes in countries like Poland, East Germany, and Hungary, the USSR aimed to spread communist ideology and secure its influence in the region. This expansion was also motivated by the desire to ensure economic and military security, as well as to counterbalance the presence of NATO and Western powers.