When the German-led Axis invasion of Yugoslavia commenced on 6 April 1941, only eight IK-2s were serviceable. One had been damaged in a landing accident, two were at the workshops in Zagreb being repaired, and the fourth unserviceable machine was in a badly damaged condition at Bosanski Aleksandrovac. That day and the next, the 107th Fighter Squadron patrolled over Bosnia but did not make any contact with the enemy. Two machines conducted a combat air patrol over the airfield of the 8th Bomber Regiment at Nova Topola. This pattern continued the following day without incident, but patrol duration and coverage was limited by the short range of the aircraft. On 8 April, a patrol unsuccessfully gave chase to a lone German reconnaissance aircraft, and later in the day, one of the IK-2s force landed, leaving seven operational aircraft.