During this period, Münster was promoted to Feldwebel (platoon sergeant) on 1 April. Based at Chuhuiv, the Gruppe participated in the Second Battle of Kharkov, the Soviet attempt to retake the city. On 20 May, Münster claimed two aerial victories, a Mikoyan-Gurevich MiG-1 fighter and an Ilyushin Il-2 ground-attack aircraft. During this engagement, he was wounded in the upper leg resulting in the presentation of the Wound Badge in Black () on 26 May. On 21 July, II. Gruppe moved to an airfield at Novy Cholan located south of Tatsinskaya. In the following days, the Gruppe fought in the Battle of Kalach, supporting the German crossing of the Don. On 24 July, Münster became an "ace-in-a-day" when he shot down five Il-2 ground-attack aircraft and a Hurricane fighter, taking his total to 30 aerial victories claimed. From 21 November 1942 to March 1943, Münster was first hospitalized in Troppau, present-day Opava, where he received surgery and then spent some time convalescing. During this period, he was awarded the Knight's Cross of the Iron Cross (Ritterkreuz des Eisernen Kreuzes) on 21 December 1942 and promoted to Leutnant (second lieutenant). At the time, he had flown 322 combat missions and had claimed 51 aerial victories. Defense of the Reich The increasing daytime attacks of the United States Army Air Forces (USAAF) Eighth Air Force against targets in western Europe forced the Luftwaffe to transfer more and more fighter units from the Eastern Front back to Germany in Defense of the Reich. On 3 August 1943, II. Gruppes air elements arrived at Uetersen Airfield in northern Germany. Münster was appointed Staffelkapitän (squadron leader) of 5. Staffel of JG 3 on 20 October 1943. He succeeded Hauptmann Heinrich Sannemann who was transferred. Münster claimed his first aerial victory over the USAAF on 13 November. That day, the Eighth Air Force targeted Bremen and Münster was credited with shooting down a Boeing B-17 Flying Fortress bomber. On 24 April 1944, Münster was temporarily put in command of II. Gruppe after its former commander Hauptmann Hermann Freiherr von Kap-herr was killed in action. Münster surrendered command to Hauptmann Gustav Frielinghaus at Gardelegen Airfield on 1 May. Since Frielinghaus was still convalescing from injuries sustained in December 1943, Frielinghaus led the Gruppe from the ground while Münster continued to lead in the air. On 8 May, Münster was killed in a mid-air collision with a Consolidated B-24