Born in Austria in 1918 and working as a baker to his late teenage years Bartels joined the "Luftwaffe" after Germany's union with Austria in 1938. Bartels completed his training as a pilot in 1941. He was assigned to "Jagdgeschwader" 26 "Schlageter" (JG 26—26th Fighter Wing) on the Channel Front which was tasked with intercepting Royal Air Force (RAF) incursions over occupied France and Belgium. He achieved his first aerial victory in August 1941. Bartels was transferred to "Jagdgeschwader" 5 (JG 5—5th Fighter Wing) on the Eastern Front where he was awarded the Knight's Cross of the Iron Cross for 46 aerial victories. In 1943 Bartels moved to "Jagdgeschwader" 27 "Afrika" (JG 27—27th Fighter Wing) to serve in the Mediterranean and Balkans theatres and by the years end had 73 victories. In 1944 he returned to the Western Front and fought Normandy Campaign in June to August 1944. Bartel's personal tally rose to 96 and he was nominated for the Oak Leaves of the Knight's Cross.