Border Agreement between Poland and the USSR of 16 August 1945 established the borders between the Union of Soviet Socialist Republics ( USSR ) and the Republic of Poland . It was signed by the Provisional Government of National Unity ( Tymczasowy Rząd Jedności Narodowej ) formed by the Polish communists . According to the treaty , Poland officially accepted the ceding its pre-war Eastern territory to the USSR ( Kresy ) which was decided earlier in Yalta already . Some of the territory along the Curzon line , established by Stalin during the course of the war , was returned to Poland . The treaty also recognised the division of the former German East Prussia and ultimately approved the finalised delimitation line between the Soviet Union and Poland : from the Baltic sea , to the border tripoint with Czechoslovakia in the Carpathians
in Yalta
Yalta Conference
Polish–Soviet border agreement of August 1945