Messerschmitt Bf.109G, Croatian users, part one.

After the Kingdom of Yugoslavia was conquered by the Axis powers, the Independent State of Croatia was formed. On 27th June 1941, shortly after the opening stages of Barbarossa, the Croatian Legion was formed by Ante Pavelic, in order to support German forces on the Eastern Front.
The aerial component, was formed shortly after, on 12th of July and was named 4. Mesovita Zrakoplovna Pukovnija (4th Mixed Air Force Regiment) which comprised two fighter squadrons, the 10th and the 11th ones.
The Fighter wing was attached to the III./JG 52, was led by Franjo Dzal and, after training in Furth and Herzogenaurach, in Germany, on Arado Ar.96 and outdated Bf.109Ds, they were set ready for combat on the Eastern Front in September 1941. They received the designation of 15. (Kroat)/JG 52.
After being equipped with the Bf.109E, they were gradually replaced with the Gustav, however the replacement rate was really slow and it wasn't until July 1942 when the first Gustavs arrived to the squadron, when they were based at Nikolayev, in southern Ukraine in the Crimean region. From July 1942 until October 1942 (when the unit was given a three-month rest period) the Gustavs flew alongside with some outdated Emils (which were gradually replaced).
During that period, many Croatian aces flew the Gustav. One of the first Croatian to flight them was Oberleutnant Ljudevit Bencetic who, by July 1942, had already a score mark of eight enemy aircraft.
Cvitan Galic, the top Croatian Ace during this period, claimed seven Soviet fighters sharing one with Ljudevit Bencetic. Galic had at least 17 kill marks outlined in black toping them with bars and red stars.

Sources:
1. https://en.wikipedia.org/wiki/Messerschmitt_Bf_109_operational_history
2. https://en.wikipedia.org/wiki/Croatian_Air_Force_Legion
3. Salamander Books - The Complete Book of Fighters