 In 1945 the frontier between Poland and Germany moved west and Brünner was one of the millions of Germans obliged to relocate as part of this militarily and politically driven process, ending up in the Soviet occupation zone of Germany which was in the process of becoming the German Democratic Republic (East Germany).In 1947 he switched to railway construction work.He joined the FDJ in 1946, and the new country's ruling SED (party) in 1948.