1951
On February 15, 1951 Aleksander Zawadzki, the president of the Polish Republic, and Andrey Vyshinsky, the Presidium of the Supreme Soviet of the Union of Soviet Socialist Republics, signed Treaty No. 6222. Agreement between the Polish republic and the Union of Soviet Socialist Republics concerning the exchange of sectors of their state territories. The treaty was a border adjustment, with Poland and the Soviet Union exchanging 480 square kilometres (190 sq mi).
Read more about this topic: Territorial Evolution Of Poland