After the Second World War, Pierre and his family spent several years in Düngenheim, Germany. It seems that his family's pro-German attitude made their departure from Luxembourg inevitable. In the summer of 1945, Pierre was arrested by French soldiers and taken to Luxembourg, where he was arrested in October by the gendarmerie in Wassertbillig. After more than 100 days in the Grund prison, Pierre was released by the juvenile court on the condition that a family member would take care of him. In the end, it was Camille Possing, an unrelated baker from Ettelbruck, who took him in as an apprentice.
Despite living abroad for some time, Pierre remained a Luxembourg citizen and had to do his military service in the Luxembourg army. He was drafted from November 1949 to May 1950. On 30 September 1950, he re-enlisted and joined the first contingent. As Soldat de 2e Classe, he fought alongside the UN troops in Korea until he fell ill at the end of March/beginning of April 1951. When his health deteriorated and he could no longer fight, he was sent home on sick leave. He spent the remainder of his military service receiving treatment in Luxembourg.

After his official discharge in September 1951, he returned to his home town of Wasserbillig, where he worked for the local tile manufacturer Cerabati. It was here that he met his future wife, Claire Ries, whom he married on 31 May 1952. Like most war veterans, "Korea Pir" preferred not to talk much about his personal Korea experiences.