1 was placed under the command of Hauptmann (Captain) Wolfgang Falck. With the start of the Norwegian Campaign in April 1940, I./ZG 1 was moved to Aalborg airfield. There, the airfield came under night attacks by Royal Air Force (RAF) Bomber Command, leading Falck to conduct his first experiments of nocturnal aerial combat. During the Battle of France, Knacke claimed an unconfirmed aerial victory on 10 May 1940 over a Bristol Blenheim bomber in the vicinity of Waalhaven. Flying numerous combat missions during this campaign, he was awarded the Iron Cross 2nd Class (), which was presented to him on 15 July 1940 and was promoted to Oberleutnant (first lieutenant) on 1 October 1940. Night fighter career Following the 1939 aerial Battle of the Heligoland Bight, RAF attacks shifted to the cover of darkness, initiating the Defence of the Reich campaign. By mid-1940, Generalmajor (Brigadier-General) Josef Kammhuber had established a night air defense system dubbed the Kammhuber Line. It consisted of a series of control sectors equipped with radars and searchlights and an associated night fighter. Each sector, named a Himmelbett (canopy bed), would direct the night fighter into visual range of a bomber. In 1941, the Luftwaffe started equipping night fighters with airborne radar such as the Lichtenstein. This airborne radar did not come into general use until early 1942. Following the Battle of France, Falck was ordered to establish the first Luftwaffe night fighter wing, Nachtjagdgeschwader 1 (NJG 1—1st Night Fighter Wing). His former unit, I./ZG 1 formed the nucleus of I. Gruppe of NJG 1 which was placed under the command of Oberleutnant Werner Streib. Now flying in the 2. Staffel of NJG 1, sources vary with respect to when Knacke claimed his first nocturnal aerial victory. According to Foreman, Parry and Mathews, he claimed a Vickers Wellington bomber shot down on 9 March 1941. According to Obermaier and Stockert, Knacke was credited with his first aerial victory on the night of 2/3 May 1941. He received the German Cross in Gold () on 14 April 1942, after his 18th claim. Squadron leader and death Knacke was appointed Staffelkapitän (squadron leader) of 1. Staffel (1st Squadron) of NJG 1 on 1 April 1942. On 25/26 June 1942, RAF Bomber Command launched the third thousand-bomber raid and bombed Bremen. That night, Knacke, assisted by his radio operator Unteroffizier Günther Heu, claimed three aerial victories. On the night of