 Complete the following phrase:  On 1 October 1941, he then took command of the III. Gruppe of Jagdgeschwader 52 JG 5252nd Fighter Wing on the Eastern Front. At the time of his posting to JG 52, III. Gruppe was based at Poltava and supporting the 17th Army in its assault on Kharkov, leading up to the First Battle of Kharkov. Under his leadership, III. Gruppe of JG 52 became the most successful fighter unit of the Luftwaffe. Von Bonin claimed his first aerial victory with JG 52 on 29 April 1942. That day, he shot down a Yakovlev Yak-1 fighter. III. Gruppe had just relocated to Zürichtal, a small village at the Inhul in the former German settlement west of Feodosia in the Crimea. On 12 May, III. Gruppe was ordered to relocate to an airfield named Kharkov-Rogan, east of Kharkov where they participated in the 