There, he was trained as a pilot which he completed in June 1940. Münster was promoted to Gefreiter (Lance Corporal) on 1 October 1940. In July 1940, Münster was transferred to the advanced Flugzeugführerschule C (FFS C—advanced flight school) at Burg bei Magdeburg where he received further theoretical training. On 1 October, he was promoted to Unteroffizier (sergeant) and transferred to the 3. Staffel (3rd squadron) of Jagdfliegerschule 3, the fighter pilot school at Fürth. World War II World War II in Europe had begun on Friday, 1 September 1939, when German forces invaded Poland. Münster completed his fighter pilot training in March 1941 and then flew some missions in Defense of the Reich from Fürth and Zerbst. On 18 March, he was posted to the 2. Staffel of Ergänzungsgruppe of Jagdgeschwader 3 (JG 3—3rd Fighter Wing). The Ergänzungsgruppe was a supplementary training group attached to JG 3 under the command of Major Alfred Müller with 2. (Schul—training) Staffel headed by Oberleutnant Erwin Neuerburg. On 1 June, Münster was transferred to the 4. Staffel of JG 3. This Staffel was commanded by Hauptmann Gordon Gollob and subordinated to II. Gruppe of JG 3 led by Hauptmann Lothar Keller. Operation Barbarossa In preparation for Operation Barbarossa, the German invasion of the Soviet Union, II. Gruppe headed 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 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. In the beginning of July 1941, the