Already before the Red Army entered Poland , the Soviet Union was pursuing a strategy of eliminating pro-Western resistance as an organized force to ensure that Poland would fall under its sphere of influence . In 1943 , following the revelation of the Katyn massacre , Stalin suspended relations with the Polish government-in-exile in London . At the February 1945 Yalta Conference , the Soviet Union agreed to allow the formation of a coalition government composed of the communists , including the Polish Workers ' Party ( '' Polska Partia Robotnicza '' , PPR ) , as well as Polish pro-Western elements in exile and in Poland , and subsequently to arrange for free elections to be held
Yalta Conference
Yalta Conference
History of Poland (1945–1989)