He was subsequently shipped to the European Theater, and first posted in England in Army camp hospitals. Just before D-Day, Fleck was posted to Bournemouth, England, to await transport over the channel with the medical (ambulance) corps. While in Bournemouth, he met Louise Harlan, an American Red Cross volunteer. Fleck stayed with ambulance corps attached to the 72nd and 76th Divisions as they moved through Belgium. He was present at the Battle of the Bulge and afterward was briefly in charge of the medical needs of some 30,000 captured German soldiers. Subsequently, he was involved in interrogating POWs and evacuating and treating concentration camp prisoners; he also traveled to several camps to search for records or other signs of surviving friends and extended family.