On 1 October 1941, he then took command of the III. "Gruppe" of "Jagdgeschwader" 52 (JG 52—52nd 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 Second Battle of Kharkov. Over the next weeks, III. "Gruppe" was moved several times. On 19 May, the "Gruppe" moved to Barvinkove where they stayed until 12 June mostly fighting over the encircled Soviet forces in the Izium salient. They were then ordered to Belgorod and to Grakowo, located approximately halfway between Kharkov and Kupiansk, on 22 June. On 26 June, III. "Gruppe" then moved to Bely Kolodez where they stayed until 3 July. According to Prien, Stemmer, Rodeike and Bock, von Bonin claimed seven aerial victories between 9 May to 30 June which were not documented.