By 15 June, JG 51 had completed its preparation for Operation Barbarossa, the German invasion of the Soviet Union and was based at airfields at Siedlce, Stara Wieś, Halasy where III. "Gruppe" was based and Krzewica, close to the German–Soviet demarcation line. The attack on the Soviet Union began at 03:45 on 22 June with JG 51 flying fighter patrols along the Bug River. The German advance into the Soviet Union required constant relocation of III. "Gruppe". On 20 July, the Gruppe was moved to an airfield at Orsha, approximately southwest of Smolensk, and flew combat air patrols along the Dnieper in the area between Mogilev and Zhlobin. Flying from Orsha, Schack claimed his first aerial victory on 23 July 1941 during the Battle of Smolensk. That day he shot down a Tupolev SB bomber northeast of Babruysk, and received the Iron Cross 2nd Class () on 10 August 1941.