What expansion plans of the Soviets led initially to which policy of the early Cold War?

The Soviet Union's expansionist policies in Eastern Europe after World War II, particularly its establishment of communist regimes in countries like Poland, Hungary, and East Germany, led to the United States adopting the policy of containment. This strategy aimed to prevent the spread of communism globally, resulting in initiatives such as the Truman Doctrine and the Marshall Plan to support countries resisting Soviet influence. The tensions from these expansionist actions and the containment response marked the early phases of the Cold War.