On 2 August 1943, JG 3 "Udet" began transferring to Western Front and flew in Defense of the Reich. The "Gruppe" arrived at Münster-Handorf Airfield the following day where they were placed under its new commander "Hauptmann" Walther Dahl. On 7 August, the unit for the first time practiced the Y-Control for fighters, a system used to control groups of fighters intercepting United States Army Air Forces (USAAF) bomber formations. Lemke claimed two USAAF Republic P-47 Thunderbolt fighters shot down on 17 August during the Schweinfurt–Regensburg mission, his first on the Western Front. By 14 October 1943, he was credited with one victory and two "Herausschüsse" (separation shots)—a severely damaged heavy bomber forced to separate from his combat box, which was counted as an aerial victory—over Boeing B-17 Flying Fortress bombers. On that day, he claimed his 129th and 130th victory, one of which was a "Herausschuss", over B-17s on their second Raid on Schweinfurt.