On 28 June, the "Wehrmacht" initiated "Fall Blau" (Case Blue), the 1942 strategic summer offensive in southern Russia. The objective was to secure the oil fields of Baku as well as an advance in the direction of Stalingrad along the Volga River, to cover the flanks of the advance towards Baku. Tasked with aerial support of this offensive was "Luftflotte" 4 (Air Fleet 4) to which JG 52 was subordinated. Following the German advance, Krupisnki had increased his number of aerial victories to twenty by the end of July. On 20 August, II. "Gruppe" reached the airfield at Tusov, approximately southwest of Kalach-na-Donu on the western bank of the Don, from where the "Gruppe" operated in the combat area of Stalingrad. Flying from this airfield, Krupinski's number of aerial victories increased to 31 by end of August.