and radar operator on this mission. Bomber Command had targeted Peenemünde and the V-weapons test centre that night. Schnaufer, who had been tasked with leading one of the first Zahme Sau missions under Y-Control, had to abort the mission early due to engine trouble. Around mid-September 1943, the two-man Bf 110 crew was augmented by a third member, sometimes referred to as Bordmechaniker (air mechanic) or Bordschütze (air gunner). The reason for this was that the decline of the Himmelbett procedure, the introduction of the broadcast procedure Zahme Sau, and the growing threat of RAF intruder night fighter operations, had necessitated the need for another pair of watchful eyes to the rear. Unteroffizier Wilhelm Gänsler, who had already contributed to 17 claims made by Hauptmann Ludwig Becker, was Schnaufer's new lookout. With Handtke and Gänsler as his crew, Schnaufer claimed his 26th aerial victory on 23 September 1943 over a No. 218 Squadron Stirling during a Wilde Sau intercept mission. Following its May 1943 debut in action, during the second half of 1943, Schnaufer and his crew began experimenting with upward-firing autocannons, dubbed Schräge Musik. This allowed the night fighter to approach and attack the bombers from below—outside the enemy crew's usual field of view. An attack by a Schräge Musik-equipped night fighter typically came as a complete surprise to the bomber crew, who realised a night fighter was close by only when they came under fire. It is not exactly known when Schnaufer's Bf 110 was equipped with Schräge Musik. Rumpelhardt stated that the weapons system was installed prior to his return from officer training. It is also not exactly known how many of his victories had been claimed using the upwards firing cannons. According to Fritz Engau, who had known Schnaufer since Flugzeugführerschule C 3, 20 to 30 of Schnaufer's aerial victories had been claimed using upwards firing guns. Rumpelhardt had returned from his officer training courses in early October 1943 and rejoined Schnaufer's crew. Gänsler, Rumpelhardt and Schnaufer claimed aerial victories 29 and 30 on 9 October. Oberleutnant Schnaufer was awarded the Knight's Cross of the Iron Cross () for 42 victories on 31 December 1943. The presentation was made by Generalmajor (lit. Major General; equivalent to Brigadier) Joseph Schmid, commanding general of the I. Jagdkorps (1st Fighter Corps), on 3 January 1944. On the night before his 22nd birthday, on 15 February 1944, Schnaufer and his