The Wehrmacht began Fall Gelb on 10 May, beginning the Battle of the Netherlands and Battle of Belgium and Battle of France simultaneously. JG 1 fought over the Albert Canal in part, protecting the bridges at the Battle of Maastricht. 3. "Staffel" engaged and claimed its first victory on 11 May in combat with 18 and 53 Squadron of the Royal Air Force. 1./JG 1 and 1./JG 27 engaged Fairey Battle light bombers of the 5/III/3, Belgian Air Force later in the day, with their fighter escort, Gloster Gladiators, 1/I/2. Only three badly damaged bombers of the original nine returned. Four of the six Gladiators were shot down by 1./JG 1—though they claimed seven. Two Fairey Fox fighters in the same area. The French Air Force Groupe de bombardement I/12 and II/12 committed 18 Lioré et Olivier LeO 45 bombers escorted by 18 Morane-Saulnier M.S.406 fighters from Groupe de Chasse III/3 and II/6; one bomber fell to fighters and flak, while four of the fighters fell to I./JG 1 and some supporting Messerschmitt Bf 110 units. On 12 May JG 1 achieved more success over the Maastricht bridges. 139 Squadron sent its Bristol Blenheim light bombers from Plivot, to the area but they ran into Stab/JG 1, 2./JG 1 and 3./JG 27. Seven of the unescorted bombers were shot down. In the first twenty-four hours, I./JG 1 and its parent unit, JG 27, flew 340 sorties and claimed 28 aircraft destroyed for four losses. JG 1 was active along the frontline on 13 May. A Westland Lysander, from the BEF, 4 Squadron. JG 27 carried out fighter escort for Junkers Ju 87 "Stukas" in the Liège area.