Poland's Post‑World War II Border Changes and Loss of the Kresy

After World War II, Poland lost its historic eastern territories—Lviv, Vilnius and Volhynia—known collectively as the Kresy. The German invasion in 1939 followed by the Soviet attack ended the Second Polish Republic’s pre‑war borders. Allied conferences in Tehran, Yalta and Potsdam redrew the map of Central and Eastern Europe, assigning the Kresy to the Soviet Union and granting Poland new lands taken from Germany in the west. The border shift forced the displacement of thousands of Poles from the east and prompted a large‑scale migration to the newly acquired western territories. The loss of the Kresy remains a point of historical debate and continues to influence Poland’s regional relations.