The end of the Phoney War on 10 May 1940 came with Operation Fall Gelb (Case Yellow), the invasion of France and the Low Countries. Stab./KG 55 had six He 111s at Leipham for the operation. The "Geschwader" was placed under the command of "Luftflotte" 3 (Air Fleet 3) although it was still subordinated to the 5th "Flieger" Division. I./KG 55 committed 35 (25 serviceable) He 111s to the offensive. II./KG 55 could muster 36 He 111s (24 operational) and 17 of 36 He 111s on strength with III./KG 55 were combat ready. The units were to be engaged in counter-air operations against the French "Armée de l'air".