Why did Stalin decline to participate in the Marshall Plan?

Stalin declined to participate in the Marshall Plan because he viewed it as a tool for the United States to expand its influence in Europe and to undermine Soviet power. He believed that accepting aid would compromise the communist regimes in Eastern Europe by fostering dependency on Western capitalism. Additionally, Stalin sought to maintain control over Eastern Bloc countries and wanted to promote his own economic model, which was based on state control and central planning. Thus, he actively discouraged Eastern European nations from participating in the plan.