Joseph Stalin wanted to prevent future threats from Germany.
Joseph Vissarionovich Stalin was a Georgian revolutionary and Soviet politician who ruled the Soviet Union from the mid–1920s until 1953 serving as General Secretary of the Communist Party of the Soviet Union as well as Premier. Stalin ruled dictatorially the Soviet Union and changed it into a major world power.
Stalin together with the Soviets felt that they needed the Eastern European nations as satellites to protect their own interests.