Later that year, Eupen was declared to be a city "Free from Jews" as its entire Jewish population is killed in concentration camps. In September 1944, American forced reached Eupen which became a centre of fierce fighting in the Battle of the Bulge. The following year Eupen was returned to Belgian control and tried its first Nazi for war crimes relating to the extermination of Jews. Trials continued until 1952.
In 1949, the left tower of the St Nikolaus Church burnt down. The city centre was affected by flooding in 1953 and demolished in 1973 to create car parks. Eupen merged with the municipality of Kettenis in 1976, amidst protest from that town. In 1980, following a state reform ten years earlier, the German-Speaking Community of Belgium was established and Eupen was named as its capital
