Joseph Stalin
Stalin invaded Poland on 18 September 1939. In the subsequent World War II, Stalin stayed neutral but signed a peace deal with Germany's leader Adolf Hitler. He then led a bloody war after Germany invaded the Soviet Union known as Operation Barbarossa, and after the end of the war Stalin gained control of all Eastern Europe including part of Germany. There, a series of loyal Marxist-Leninist single-party states were set up, extending his power and making the Soviet Union a superpower.