His training had qualified him to fly 17 different types of powered aircraft, and, following his graduation, he was posted on 21 August 1942 to "Ergänzungs-Jagdgruppe Ost" (Fighter Supply Group, East) in Gleiwitz, Upper Silesia, where he remained until 10 October 1942.
Hartmann je pozneje povedal, da mu je ta dogodek rešil življenje:Potem se je Hartmann popolnoma posvetil študiju.