As a result of Joseph Stalin 's policy of expansion to the west , it was decided during the Yalta Conference that the Polish eastern border shall be set along the so-called " original " Curzon Line . Based on this decision , the left-bank part of Grodno town would be kept within the borders of Poland . It is actually not clear till today , how the original Curzon Line near Grodno has been moved by around 20 km to the west . When the so-called " mistake " ( today regarded rather as deliberate sabotage within British ministry structures ) became obvious to negotiators , Stalin refused to correct the mistaken line . Despite multiple and desperate appeals from Polish citizens of Grodno , the whole Grodno region , ( including ethically Polish till today ) Sapotskin Triangle , was incorporated to the Soviet Belarus and many Poles emigrated or were expelled
Yalta Conference
Yalta Conference
Grodno Region