The time when Petrovic flew this machine is the end of June 1937. Fighting in Spain as a volunteer, in order not to cause any trouble to his family back home in Belgrade, he took the pseudonym Fernandez Garcia. He took over his I-15 in the end of June 1937, in Murcia, where it was an assembly line for the aircraft, shipped in parts from Soviet Union. At this time, 1a Escuadrilla de Chatos was based in El Coto airfield, 26 km north-east from Madrid, in between the cities Alcala de Henares and Guadalajara. The unit was engaged at many fronts, specially in the defense of Spanish capital. The squadron Commander was major Ivan Eremenko, while the 'Teniente Garcia's' wingman was another Soviet volunteer Leonid Rybkin.
From July 1st to July 12th 1937, Petrovic was flying this aircraft in about 30 missions, but after it there is no data. Still, it is recorded that from July 1st to July 7th, Petrovic shoot down 3 Fiats CR.32 and a single Heinkel He.51. And then, in July 8th, north from city of Avila (some 100 km from Madrid), during the massive air duel with numerous fighters on the both sides, Petrovic manage to shut down the Messerschmitt Bf.109B. According to some, this was the very first shot down Bf.109 in Spanish Civil War. Few days later, near the Madrid, he shot down the Heinkel He.111B bomber.
Petrovic quickly became popular. His face was even on the posters on the walls of Paris, the Interbrigade recruitment center, calling for the new volunteers to help the Republic. In order to save a brilliant pilot, in a highest military circles the decision was made: to withdraw Petrovic from the battle and send him to Soviet Union, since the authorities of Kingdom of Yugoslavia were put him outlaw. Still, the decision did not prevent Petrovic to break the orders and, on the July 12th and probably on some other Chato, he shoots down another Fiat CR.32. It was his 7th and the last victory.
Bozidar Bosko Petrovic died in July 18th, 1937, at the age of only 26 (he was born in April 11th, 1911), and there are two versions of his death. Soviet military sources claim that he is shot down in a battle with two enemy fighters, while the other source states that, fighting a single Fiat CR.32, Petrovic probably suspects that enemy pilot tries to avoid the battle and dive after him. When the Fiat crashed, Petrovic begin to pull out his fighter from diving, but the aircraft's construction did not withstand. He unsuccessfully tried to regain control and crashed in a near valley. The whereabouts of its body remains unknown, but probably in a mass grave at Brunete.
The red wingtips and the red belt around the fuselage were standard insignia of the Republican Air Force established at the very beginning of the war. A pre-war tricolor of a Second Spanish Republic (red-yellow-purple) remains in tail, with large white squadron number 13 over it and white ring in front of it. The ring around the engine is black. Upper surfaces were dark-green, while the lower were light-blue.