 Complete the following phrase:  In June 1941, the unit under Wietersheim participated in Operation Barbarossa, where, as part of the First Panzer Group, it served with Army Group South on the southern sector of the eastern front, advancing via Lvov, Tarnopol and Zhitomir to Kremenchug and Mirgorod, and south to Marfinskaya in the Mius sector. The corps spearheaded First Panzer Groups difficult and impressive drive to Kiev during the Battle of Kiev 1941, and participated in the 