In parallel, he was accepted for flight training with the Deutsche Verkehrsfliegerschule, a covert military-training organization, and at the Lipetsk fighter-pilot school.

Initially based at Pardubitz, present-day Pardubice in the Czech Republic, the Gruppe was equipped with the Messerschmitt Bf 110 C-1 heavy fighter.

[8] During the prelude of World War II on 25 August 1939 I. Gruppe of ZG 76 deployed to an airfield at Ohlau to the southeast of Breslau.

[9] On Friday 1 September 1939, German forces invaded Poland starting World War II in Europe.

[11] In October, the unit was then relocated, at first to Bönninghardt and on 16 December to Jever, to protect the northern seaboard and the Kriegsmarine naval bases.

[12] During the Battle of the Heligoland Bight on 18 December 1939, he was credited with the destruction of a Royal Air Force (RAF) Vickers Wellington twin-engine bomber on a mission to Wilhelmshaven.

[17] In February 1940, Hauptmann Falck was appointed Gruppenkommandeur of I. Gruppe of Zerstörergeschwader 1 (ZG 1—1st Destroyer Wing), based at Düsseldorf.

[15][18] On the night of 30 April and 1 May, 50 RAF Armstrong Whitworth Whitley, Vickers Wellington and Handley Page Hampden bombers attacked Luftwaffe airfields in Norway.

Falck, his comrade from "K 31" Radusch, Oberleutnant Werner Streib, and another pilot, followed the bombers shortly before sunup on their flight back to England.

Following this encounter, Falck submitted a comprehensive tactical report on his night interception ideas and experiences to the Reichsluftfahrtministerium (RLM—Ministry of Aviation).

Shortly after, Generaloberst Erhard Milch, at the time a state secretary in the RLM and temporary commander of Luftflotte 5 (Air Fleet 5), visited Falck and discussed his ideas personally with him.

On 22 June 1940, General der Flieger Albert Kesselring called Falck that Hermann Göring, commander-in-chief of the Luftwaffe, had tasked him with the creation of the first night fighter unit.

[20] During the meeting, Göring appointed Falck as Geschwaderkommodore and tasked him with creation of Nachtjagdgeschwader 1 (NJG 1—1st Night Fighter Wing).

The emblem, which in parts was based on Falck's family coat of arms, depicts a silver falcon on the dark sky with a red lightning bolt over a section of the globe pointing at London.

[25][26] He was to command NJG 1 for three years and in partnership with General Kammhuber develop a highly effective night fighter force.

Falck was then sent to Berlin and appointed within the Luftwaffenbefehlshaber Mitte, as overall responsible for the day and night fighter defence of the Reich.

In March 1945 he was given command of fighters based in the Rhineland, but did not take up the role, becoming a prisoner of the American Forces on 3 May 1945 in Bavaria.