According to an essay by Hagen Dirck Sanders, which details what Beuys' experiences may have been like during World War II, military experts argue whether the Stuka JU 87--the type of airplane in which Beuys flew as a radio operator during the first years of the war and which was widely used by the German Luftwaffe was highly operational--"successful"--or not. Also according to Sanders, near the end of the war the need for new German pilots and the development of new flight technology caused the airforce to retrain pilots to fly a new kind of airplane.