Despite the favored acquisitions abroad by the VVKJ conservatives, in the early 1932 an idea to develop a modern combat airplane was initiated by two young Serbian engineers, Ljubomir D. Ili? and Kosta I. Siv?ev, who were at the time employed at the Air Force Command Technical Department. They worked in secret after hours at Ili?’s apartment and designed the first entirely Yugoslav made fighter airplane, the IK-L1, which first took off on 22 April 1935. The second prototype, IK-02, construction began ten months later and the airplane took off for the first time on 24 August 1936. The first 12 series airplanes construction followed in 1937 with the last airplane entering service in February 1939. At the time of the German attack, on 6 April 1941, VVKJ could rely on eight IK-2s, which served with distinction during the short and bloody April war.