In support of "Fall Rot" (Case Red), the second phase of the conquest of France, II. "Gruppe" was subordinated to the "Stab" of JG 2 and ordered to Monceau-le-Waast on 4 June. On 5 June, together with the other elements of JG 2, II. "Gruppe" fought over the combat area of the 6th and 9th Army. In contrast to the other groups of JG 2, II. "Gruppe" pilots claimed just one aerial victory on 6 June and another on 13 June. As German ground forces advanced towards the Aisne, the "Gruppe" faced less aerial opposition resulting in more ground support missions flown. Following the Armistice of 22 June 1940, combat operation concluded on 25 June. On 27 June, II. "Gruppe" was ordered to Beaumont-le-Roger, patrolling the English Channel and participated in the occupation of Guernsey on 1 July. Schellmann claimed his first aerial victory during the Battle of Britain on 18 July when he shot down a Bristol Blenheim bomber north of Le Havre. On "Adlertag", 13 August, he led II. "Gruppe" on a fighter sweep, clearing the airspace for the Luftwaffe bombers. Flying with the "Geschwaderstab" on 25 and 27 August, Schellmann claimed a Spitfire shot down near Warmwell and another Spitfire near Wareham. On 31 August, he shot down a Hurricane near Eastchurch also flying the "Geschwaderstab". At the time, Schellmann was already considered to become the next "Geschwaderkommodore" (wing commander) of JG 2.