A number of changes had taken place in the five months since the Yalta Conference that greatly affected the relationships among the leaders. The Soviet Union occupied Central and Eastern Europe, and the Red Army effectively controlled the Baltic states, Poland, Czechoslovakia, Hungary, Bulgaria, and Romania. Refugees were fleeing from those countries. Stalin had set up a puppet communist government in Poland, insisted that his control of Eastern Europe was a defensive measure against possible future attacks, and claimed that it was a legitimate sphere of Soviet influence.