Poland 's eastern borders had not become a major international issue , as the Western powers accepted the Soviet position in this regard . Decisions concerning the Polish – German border were made at the Potsdam Conference , where Stalin lobbied for Poland 's maximal extension in the west , arranged for the Polish government delegation to present their point of view and in the end thwarted the long-standing British policy ( aimed at keeping some of the lands in question for the future German state ) . In Poland , the PPR led the massive " Recovered Territories " propaganda campaign , the Allied-authorized expulsion of ethnic Germans and the repopulation of the region by Poles " repatriated " from the lost Kresy eastern areas . The exact eastern boundary was determined in the Polish – Soviet treaty signed on 16 August 1945 , which finalized the contested issue of Lviv ( the city stayed on the Soviet Ukrainian side of the border ) . The resettlement of Ukrainians who lived on the Polish side followed
Potsdam Conference
Potsdam Conference
Polish Workers' Party