Trautmann joined the Luftwaffe as a radio operator in 1941. During training, he showed little aptitude for radio work, and transferred to Spandau to become a "Fallschirmjäger" (paratrooper). He served first in Occupied Poland, though being stationed far behind the front line resulted in boredom for his regiment, which resorted to sports and practical jokes to pass the time. One such practical joke involving a car backfired on Trautmann, resulting in a staff sergeant burning his arms. Trautmann was court-martialled, and received a three-month prison sentence. At the start of his confinement, Trautmann came down with acute appendicitis, and spent the remainder of his sentence in a military hospital.