The trouble started when they started flying combat missions together. Grislawski immediately noted that the newcomer was one of those who thought they were going to "shoot together a Knight's Cross" in no time. Hartmann barely had started to leave his place behind Grislawski's aircraft to direct his Bf 109 against an I-16, when his earphones seemed to explode:
"You bloody idiot! What the hell are you think you're doing? I'm your leader! Get back in place or I'll shoot you down!"
Grislawski kept cursing over the R/T all the way back to base, and when they had landed, the Oberfeldwebel gave the Leutnant a dressing down that he would never forget. Then - in front of the sweating Hartmann - Grislawski turned to his friend "Paule" Rossmann and said:
"Oh man, this is too much! What a baby they have sent us! Just look at his face - like a cute little boy!"
From then on, Grislawski never addressed Hartmann otherwise than as Bubi, "Little boy."