Wilcke then fought in the aerial battles of Operation Barbarossa, the German invasion of the Soviet Union. There, after 25 aerial victories, he was awarded the Knight's Cross of the Iron Cross on 6 August 1941. In September 1941, he relocated with his group to the Mediterranean Theater, where he was able to claim further victories. At the end of May 1942, he was transferred to the "Stab" (headquarters unit) of "Jagdgeschwader" 3 (JG 3—3rd Fighter Wing) "Udet", and that August he was appointed as its "Geschwaderkommodore" (wing commander). Following his 100th aerial victory on 6 September, he received the Knight's Cross of the Iron Cross with Oak Leaves. During the Battle of Stalingrad, on 17 December, he claimed his 150th aerial victory. On 23 December 1942, he was awarded the Knight's Cross of the Iron Cross with Oak Leaves and Swords, his total now 155 aerial victories.