After World War II the region fell into the Soviet Union 's Zone of Occupation . They then illegally placed it under their puppet Polish administration , with Stalin simply announcing this at the Potsdam Conference under territorial changes demanded by the Soviet Union . Most Germans fled or were expelled leaving behind their town , homes and virtually all their belongings . They were then replaced with Poles , some of whom expelled from the Polish areas annexed by the Soviet Union or Ukrainians forced to settle in the area through Operation Vistula in 1947
Potsdam Conference
Potsdam Conference
Olecko