Valetta. This aerial victory was claimed during the action which resulted in the sinking the British submarine . II. Gruppe flew its last combat mission over Malta on 25 April. The following day, the unit began its relocation to Pilsen where they arrived on 27 April. Eastern Front II. Gruppe had been ordered to the Eastern Front in preparation for Case Blue, the strategic summer offensive in southern Russia. While based at Pilsen, Hauptmann Kurt Brändle took over command of the Gruppe after Krahl had been killed in action over Malta. The Gruppe was then deployed on the left wing of Army Group South where it was based at Chuhuiv near the Donets on 19 May. On 21 May, II. Gruppe fought over the combat area of the 6th Army northeast of Kharkov. There, Kirschner claimed a Ilyushin DB-3 bomber shot down, his first aerial victory on the Eastern Front. Squadron leader In late August 1942, II. Gruppe was withdrawn from the front and ordered to Neuhausen near Königsberg, present-day Guryevsk, for reequipment with the Bf 109 G-2. There, Moldenhauer, the commander of 5. Staffel was transferred. In consequence, Kirschner became the designated Staffelkapitän (squadron leader) of 5. Staffel. On 9 September, the Gruppe was ordered to Smolensk where it was subordinated to Jagdgeschwader 51 (JG 51—51st Fighter Wing). He received the Honor Goblet of the Luftwaffe () and the German Cross in Gold () after claiming 51 aerial victories. On 27 April 1943, Kirschner was credited with his 100th aerial victory over a Douglas A-20 Havoc named "Boston". He was the 37th Luftwaffe pilot to achieve the century mark. In early May, II. Gruppe was moved to Kharkiv, from where they operated over the combat area east of Belgorod, operating in this area from 2 to 6 May. On 6 May, the Gruppe claimed twelve aerial victories, including four by Kirschner, taking his total to 113. Kirschner claimed his 150th aerial victory on 5 Juli 1943, the first day of Operation Citadel, the German offensive phase of the Battle of Kursk. Preempting the German attack, Soviet aircraft attacked the German airfields in the early morning. Fighting in the aerial battles that day, Kirschner claimed nine aerial victories, his third "ace-in-a-day" achievement. That day, II. Gruppe intercepted Il-2 ground attack aircraft from 66 ShAP (Shturmovoy Aviatsionnyy Polk—Ground-attack Aviation Regiment) and 735 ShAP. Following his 170th aerial victory he received the