Airport in Poland, via Straubing. Operation Barbarossa In preparation for Operation Barbarossa, the German invasion of the Soviet Union, II. Gruppe headed further east on 18 June. Following a stopover at Kraków, the unit was moved to Hostynne. At the start of the campaign, JG 3 under the command of Major (Major) Günther Lützow was subordinated to the V. Fliegerkorps (5th Air Corps), under the command of General der Flieger (General of the Aviators) Robert Ritter von Greim, itself part of Luftflotte 4 (4th Air Fleet), under the command of Generaloberst (Colonel General) Alexander Löhr. These air elements supported Generalfeldmarschall (Field Marshal) Gerd von Rundstedt's Army Group South, with the objective of capturing Ukraine and its capital Kiev. At 17:00 on 21 June 1941, the 5th Air Corps, based at Lipsko, briefed the various unit commanders of the upcoming attack. That evening, Gruppenkommandeur (group commander) of II. Gruppe Lothar Keller informed his subordinates of the attack. The invasion of the Soviet Union began on 22 June 1941. II. Gruppe flew its first missions on the Eastern Front shortly before 04:00, flying low attacks against Soviet airfields in the vicinity of Lvov in Ukraine. At 06:30 the Gruppe fought its first aerial battles. 4. Staffel claimed three victories and the Gruppenstab four. In the beginning of July 1941, the front in the vicinity of the northern sector of Army Group South became increasingly fluid. This necessitated the relocation of II. Gruppe to Volodymyr-Volynskyi. On 2 July, II. Gruppe claimed 23 aerial victories in the combat area west of Berdichev and Zhitomir, including the first aerial victory by Lucas. The rapid advance of German ground forces required II. Gruppe to move to Lutsk on 5 July, then to Dubno that evening and to Miropol on 10 July. That day, Lucas claimed three Tupolev TB-3 bombers shot down. He and his wingman, Oberleutnant (First Lieutenant) Franz Beyer, had encountered twelve TB-3s from 14 Tyazhyolyy Bombardirovochnyy Aviatsionnyy (14 TBAP—14th Heavy Bomber Aviation Regiment). The two pilots claimed five of the bombers destroyed while Soviet records indicate that seven were lost. On 8 August 1941, Lucas became an "ace-in-a-day" for the first time, shooting down five Soviet bombers in combat near the Dnieper river. On 31 October 1941, II. Gruppe flew its last combat mission over the northern Crimean combat zone and was ordered to retreat to Germany for a period of rest and refurbishment.