As the Soviet forces began their westward offensive with the victory at Stalingrad , it had become increasingly apparent that Stalin 's vision of a future Poland and of its borders was fundamentally different from that of the Polish government in London and the Polish Underground State ; the Polish-Soviet relations kept deteriorating . Polish communist institutions rival to those of the main national independence and pro-Western movement were established in Poland in January 1942 ( the Polish Workers ' Party ) and in the Soviet Union ( the Union of Polish Patriots ) . Early in 1943 , the Polish communists ( their delegation led by Władysław Gomułka ) engaged in Warsaw in negotiations with the Delegation of the Government-in-Exile , but no common understanding was arrived at and the Delegation terminated the talks after the Soviet-Polish breach in diplomatic relations caused by the dispute concerning the Katyn massacre . The Polish Workers ' Party formulated its separate program and from November was officially under Gomułka 's leadership . On the initiative of the Union of Polish Patriots , presided by Wanda Wasilewska , in the spring of 1943 the Soviets began recruiting for a leftist Polish army led by Zygmunt Berling , a Polish Army colonel , to replace the " treacherous " Anders ' army that left . The Kościuszko Division was rushed to its first military engagement and fought at the Battle of Lenino on 12 – 13 October . The Soviet-based communist faction , organized around the Central Bureau Communists of Poland ( activated January 1944 ) , directed by such future Stalinist Poland 's ruling personalities as Jakub Berman , Hilary Minc , and Roman Zambrowski , was increasingly influential . They also had a prevailing sway on the formation of Berling 's First Polish Army in 1943 – 44
Katyn massacre
Katyn massacre
History of Poland (1939–1945)