command of the wing. By the end of May, all of JG II's squadrons except Jagdstaffel 19 (Jasta 19) had new Staffelführern (squadron commanders). Berthold also fulfilled a request from 18th Armee headquarters for an appreciation of the new wing's operations. His 28 April memorandum delineated the differences between the earlier ad hoc Jagdgruppe and the more recent Jagdgeschwader. The Jagdgruppe, consisting of several squadrons temporarily grouped together, concentrated its efforts on shielding nearby German reconnaissance and artillery direction two-seaters from Allied attacks. On the other hand, an Armee headquarters could launch a Jagdgeschwader anywhere along the Armee's front to counterattacking Allied flights, whether fighters or bombers. Berthold proposed having air defense officers trail along with the front-line infantry to report incoming enemy aircraft to JG II. He also asked for, and received, sufficient motor transport for JG II to quickly shift bases as it followed the ground fighting. On 8 May, Berthold's aggressive leadership led to him being entrusted with deploying all of the fighter aircraft attached to 18th Armee. Indeed, by 20 May, JG II had 57 confirmed victories while in support of Operation Michael. However, on 26 May, Jasta 12 and Jasta 19 were both grounded for lack of aircraft. And, by late May, the new Siemens-Schuckert D.IIIs supplied to the wing had been returned to their factory for modification. Their departure left the already understocked wing very short of serviceable aircraft, but the Siemens-Schuckert D.IIIs were experiencing engine failures in as little as seven hours running. Their Siemens-Halske Sh.III 11 cylinder counter-rotary engines were lubricated with synthetic castor oil, and failing for lack of actual, organic-base castor oil. Berthold's return On 27 May, the depleted JG II was detailed to cover the start of the Aisne Offensive with high altitude patrols against invasive Allied aircraft, ending in trench strafing. On 28 May, Rudolf Berthold returned to the air. He had acquired a new Fokker D.VII, and thought he could fly it because of its sensitive controls. He promptly scored his 29th victory while ignoring the pain of his festering arm. The success left him feeling he had gained additional control over his unit. He could now demonstrate his adherence to his iron code of combat to his pilots. He insisted that none of his pilots could turn back for engine trouble, jammed guns, or depletion of ammunition. Despite JG II's boost in morale at Berthold's return,