In 1945 , near the end of World War II , Mehlsack , including its castle , was 90 per cent destroyed by fighting and was conquered by the Soviet Red Army . The town was placed under Polish administration under border changes demanded by the Soviet Union at the postwar Potsdam Conference . Most of the remaining German-speaking residents were expelled and replaced with Poles , many of whom had themselves been expelled from Polish areas annexed by the Soviet Union . The town was renamed from Mehlsack to '' ' Pieniężno ' '' after Seweryn Pieniężny ( 1890-1940 ) , an editor for the Polish-language newspaper '' Gazeta Olsztyńska '' in Olsztyn , imprisoned and murdered by the Germans during World War II
Potsdam Conference
Potsdam Conference
Pieniężno