On 12 March 1945 during World War II , refugee-crowded Swinemünde suffered heavy destruction by the USAAF , an estimated 5,000 to 23,000 were killed , most of whom are buried on the Golm War Cemetery west of the town , on the German side of the border . The unfinished was scuttled in the harbor in an attempt to prevent its capture by the advancing Red Army ( it was nevertheless refloated by the Soviets later ) . The German battleship had also participated in the defence of the city , before it too was scuttled . After the German forces defending the city were evacuated , Soviet forces occupied the city on the night of 4 – 5 May 1945 . After Germany 's defeat in the war , the Soviet Union imposed new borders in eastern Europe at the Potsdam Conference , which made Świnoujście part of Poland once again . The German – Polish Border Treaty of 1990 officially affirmed the existing borders after the fall of the Iron Curtain . In the winter of 1945 , some members of the communist Polish Security Forces who had been victims of German concentration camps and other German atrocities acted in revenge against local Germans . An investigation in 2008 estimated that over 40 German civilians were killed . Nine men were charged with the murder and maltreatment of Germans , and in 1947 , after one escaped and one hanged himself , seven of them stood trial . The harshest sentence given in that trial was 4 years imprisonment , for theft . In another trial , the town 's chief of police , Jan Zientara , was sentenced to eight years , for organizing robberies of German civilians
Potsdam Conference
Potsdam Conference
Świnoujście