What action did the Western Allies take after World War 2 that caused the Soviets to strengthen their hold on East Germany?

After World War II, the Western Allies implemented the Marshall Plan to aid in the economic recovery of Western Europe, including West Germany. This move was perceived by the Soviets as a direct threat to their influence in Eastern Europe. In response, the Soviets tightened their grip on East Germany, solidifying their control and establishing a more repressive regime to counter Western influence and prevent the spread of capitalism. The division of Germany became a focal point of the broader Cold War tensions.