Many of them had previously served in the Royal Yugoslav Air Force in April 1941 during the Nazi Invasion of Yugoslavia.

Some of them also had experience in the two main types that they would operate, the Messerschmitt Bf 109 and Dornier Do 17, with two fighter pilots having actually shot down Luftwaffe aircraft.

During operations over the Eastern Front, the unit's fighters scored a total of 283 kills while its bombers participated in 1,332 combat missions.

[2] It was then absorbed by the Air Force of the Independent State of Croatia and its surviving members fought back on Croatian soil.

One squadron of the Fighter Wing was sent to the area of Furth, Germany, for training, the other to Herzogenaurach Airfield, nearby.

Attacks were made on Soviet armoured columns around Pokorovskoje, Matvejeva, Kurgan, Jeiska and Uspenskoje, and on the railway line Marinpol-Stalino.

In April 1942, the Squadron flew escort missions for Stuka bombers, guarded the Marinpol airfield, and strafed Soviet troops in the Azov Sea area.

From this base of operation, the Squadron flew escort missions for bombers attacking Sevastopol and patrolled the Azov Sea area.

[1] The Squadron continued with its fine performances until March 1944 when the Luftwaffe decided that attempting to maintain 15./JG 52 was futile, and the men were sent home to the NDH to help to combat the increasing air activity over the Balkans by the Allies.

At least part of the unit returned to the Eastern Front when, at the beginning of July, the Luftwaffe reconsidered its decision.

They were transported to Romania and then the Slovak Republic, but no aircraft were provided, and on 21 July the pilots were advised that the HZL was to be disbanded.

At the beginning of September they flew to Lithuania in preparation to rejoin the fray, but the defection of squadron leader Mato Dukovac led to the cessation of Croat aerial operations on the Eastern Front.

The rest of the Bomber Squadron's assignments were in the Northern Sector of the Eastern Front, including the bombing of Leningrad and Moscow.

After flying some 1,500 sorties on the Eastern Front, the Squadron and its aircraft were re-deployed to Croatia in December 1942, to help combat the growing Partisan threat to the Axis forces in occupied Yugoslavia.

By the end of 1944 the squadrons had handed in their remaining worn-out Macchis for brand new German Messerschmitt Bf 109G & K fighters.

Over 50 Messerschmitts were delivered to the squadrons and the Air Force of the Independent State of Croatia, with the final delivery taking place on 23 April 1945.

The Dorniers proved a welcome addition to the strike power of the Axis forces fighting the Partisans in occupied Yugoslavia right up to the end of July 1944, when it was incorporated into the ZNDH.