The Air Force of the Independent State of Croatia (; ZNDH), was the air force of the Independent State of Croatia (NDH), a puppet state established with the support of the Axis powers on the territory of the Kingdom of Yugoslavia during World War II. The ZNDH was founded under German authority in April 1941, following the German-led Axis invasion of Yugoslavia.
Although it could not be considered a large air arm in the wider context of World War II, the ZNDH nonetheless had on its charge at one time or another some 650 aircraft between April 1941 and May 1945, as well as anti-aircraft and paratroop units. From humble beginnings in 1941, the ZNDH was still providing some measure of air-support (fighter, attack and transport) until the last days of World War II in Europe.
The ZNDH maintained a flying training school equipped with gliders and trainers, originally at Rajlovac airfield near Sarajevo and then at Velika Gorica and Pleso airfields in Zagreb. Its parachute and paratroop school was located in Koprivnica.
History
Establishment The ZNDH came into being as early as 19 April 1941, just nine days after the proclamation of the NDH. Its commander was Colonel Vladimir Kren, a former captain of the Royal Yugoslav Air Force (; VVKJ), who had defected to the Germans in Graz in his Potez 25 on 4 April 1941 and declared himself an Ustaše supporter.
The first task of the new air force, the backbone of which was provided by 500 former VVKJ officers and 1,600 NCOs, was the acquisition or salvage of aircraft, weapons, machinery, equipment and fuel that had survived the fighting and had not been confiscated by the German or Italian forces.
Following the brief April War, the Germans had captured over 300 ex-VVKJ aircraft. They considered them to be of little use for the Luftwaffe, so it was decided to equip the ZNDH with an appropriate number of these aircraft. These aircraft, scattered in every corner of Yugoslavia, were then collected, minor damage repaired and stocks of fuel and spare parts stored at airfield workshops. Naturally, the majority of the aircraft were more or less damaged and action was undertaken to repair as many of them as possible. Former VVKJ pilots of Croatian background and other personnel of aeronautical specialty were approached and offered instant rehabilitation (most of them were in German POW camps), jobs and safety for their families.
Kren also initiated the formation of an early warning system, anti-aircraft batteries (armed with German and Czech weapons) and various training and servicing departments, ammunition stores and workshop facilities. The fuel necessary for the operations of the ZNDH was supplied by the Germans from former Yugoslav stocks in Kraljevo, Serbia.
As early as May 1941, the NDH had asked Germany for, among other things, 22 Messerschmitt Bf 109s. Instead, they got some of the remaining largely obsolete aircraft of the VVKJ. At the same time, Germany appropriated six captured Dornier Do 17K bombers, which were then supplied to Bulgaria. Romania received six ex-VVKJ Hawker Hurricanes, as well as six Bristol Blenheims, whilst Finland received 20 half-completed Blenheims, together with manufacturing tools and production equipment, as well as a huge variety of spare parts.
During the middle part of 1941, some of the ZNDH's man-power capacity (one fighter squadron and one medium bomber squadron) was sent to the Eastern Front as part of the Luftwaffe, the Croatian Air Force Legion (; HZL; ). Most of the Croatian Air Force Legion's personnel were back on NDH territory by late 1942 (bomber squadron)/early 1944 (fighter squadron) to help counter the growing Allied air threat.
The personnel of the ZNDH took over and re-activated the airfields at Zagreb, Sarajevo, Mostar, Banja Luka and Zemun, where the Ikarus and Zmaj aircraft plants were located. By June 1941, the Germans had begun to pass on to the ZNDH various captured VVKJ aircraft, including eight Bristol Blenheim I and five Potez 25 bombers. These and most of the 211 ex-VVKJ aircraft received by the ZNDH had first to be repaired and/or overhauled at the Ikarus plant in Zemun.
The first missions: 1941
In late 1941 the ZNDH had 95 aircraft distributed in four groups and eight squadrons. Fighting the Yugoslav Partisans from the air had begun already in late June 1941, when Breguet 19 and Potez 25 bombers had proved most suitable. The Breguets could carry a bomb load of up to using 24 bombs, whilst the Potez 25s could carry about half that amount. Both types were also armed with three machine guns. Altogether the ZNDH eventually came to possess 50 Breguet 19s and 45 Potez 25s. The operational use of these light bombers was not limited to fighting the Partisans; the aircraft were also used to supply isolated or surrounded army strong points.
The emblem of the ZNDH was to be the red and white chequerboard insignia, (), derived from the Croat coat of arms, dating back to the 10th century, carried on the fin. In January 1945 this was replaced by the black and white trefoil cross of King Zvonimir.
As well as the Breguet and Potez aircraft, which were the most numerous types in the ZNDH inventory, Zmaj Fizir FP-2 light biplane trainers were also converted to carry six bombs. These aircraft were used to bomb and strafe Partisan troops and positions in northern Bosnia but they also faced anti-aircraft fire. The first missions cost the ZNDH a Breguet and a Potez aircraft, both of which crash landed after being hit by Partisan ground fire. The ZNDH crews had little chance of survival after being hit, as flying suits, helmets and parachutes were not available at the time – hence their desperate crash-landings.
Similar actions continued throughout 1941. The ZNDH flew many missions in support of Army troops in limited scale operations against the Partisans mostly over eastern and western Bosnia, as well as over other parts of the NDH. By September, the ZNDH introduced larger aircraft for bombing Partisan forces and territory. Two bombers, an Avia Fokker F.IX derived F.39 and a Savoia-Marchetti SM.79 were available for operations and had the added advantage of being able to carry bombs. They were extensively used for bombing villages and road communications. However it was soon established that the vintage biplane Breguet 19 and Potez 25 aircraft were ideally suited for missions against Partisan troop concentrations. Although they were outdated and certainly their use would be out of the question on any other front, their performance and armament made them very dangerous for an ill-armed enemy. The Partisans were scattered in villages, forests and mountains and their positions could only be detected by a slow moving aircraft. Visual reconnaissance missions using hand-held cameras were also flown. Aerial reconnaissance supplied the army with vital data about Partisan movements and positions and about the situation in Partisan territory in general. This was all the more important because the army desperately lacked radio equipment of all kinds. Light aircraft were frequently used for liaison duties, particularly connecting the surrounding army garrisons and higher command. Often the Army requested one or two aircraft to be temporarily attached to particular army units to closely co-operate with ground troops.
The ZNDH's fighter force was poorly equipped in every respect, consisting of 12 ex-VVKJ machines including four Ikarus IK-2s, seven ancient Avia BH-33 Es and one Hawker Fury II. Fortunately for this ill-equipped force, there was no aerial opposition and some more modern fighter aircraft were received from 1942 onwards.
Colder October and November weather limited aerial activities over the NDH. The Partisan operations spread to eastern Serbian territory and the squadrons based at Sarajevo airfield made their appearance on the Bosnian-Serbian border area. The Partisans were trying to secure and expand their territory in the eastern part of Yugoslavia, which they had liberated in the autumn of 1941. The ZNDH flew daily supply missions with their Avia Fokker F.39 and due to the lack of other aircraft also used the venerable Breguets and Potez. These could land on hastily prepared strips and performed very well in airlifting supplies to the surrounded garrison of Višegrad.
Expansion: 1942
In 1942, fighting with the Partisans intensified. Not only had they liberated a substantial territory in the eastern part of Yugoslavia, but they encouraged rebellion all over the country. The German, Italian and NDH governments were aware of this danger and they used every means available to destroy the Partisan forces. They planned several large-scale operations for this purpose in which air support played a very important role.
The first half of 1942 was marked by several deliveries of new or refurbished aircraft from Germany and Italy, aside from those received from Ikarus in Zemun. First of all the ZNDH received 10 brand new Caproni Ca.311 M medium bombers from Italy. These aircraft had been ordered and paid for by the Yugoslav Government for service in the VVKJ, but the Axis invasion of Yugoslavia prevented delivery. The ZNDH also purchased 20 AVIA FL.3 basic trainers, nine Fiat G.50bis fighters and one Fiat G.50B two-seat fighter trainer. The Fiat aircraft were to provide the ZNDH's fighter pilots with some operational training on more modern aircraft.
Other batches of overhauled ex-VVKJ aircraft also arrived from the Ikarus aircraft plant in Zemun, including 11 Dornier Do 17K, three Bristol Blenheim Mk I and one Caproni Ca.310 bombers, 15 Rogožarski PVT and 11 Rogožarski R-100 attack aircraft, which had been fitted with bomb racks to carry bombs, plus a few Breguet 19s, Potez 25s, Zmaj Fizir FNs and Zmaj Fizir FP-2s. From Prague in Czechoslovakia (under German occupation), the ZNDH received seven Avia Fokker F.7 transports, one Avia Fokker F.9 and one Avia Fokker F.18. Of these, the F.7s and F.18 were pre-war Czech airliners. As the ZNDH suffered from a total lack of transport aircraft, these were immediately pressed into service, after only minor adjustments. Some were even used to provide scheduled air-line services.
The nine Fiat G.50bis fighters took off from Turin-Fiat Aviazione on 12 June 1942, but before crossing the border they were stopped by an order from Capo di Stato Maggiore Cavallero, that was afraid the ZNDH pilots could defect with the new Fiat aircraft. The G.50 aircraft had to wait until 25 June before being delivered to the 16th Squadron at Banja Luka, but during the course of 1942, five were transferred to the 1st Squadron stationed in Zagreb in order to strengthen the defence of the NDH capital. Their deployment between the two squadrons was aimed to further familiarise the ZNDH fighter pilots with more sophisticated aircraft. Until that time, the only fighters available in numbers were the seven ancient Avia BH-33E biplanes and four Ikarus IK-2 gull wing fighters (for which there were very few spares), as well as 11 Rogožarski R-100 parasol wing fighter-trainers.
Thanks to this extended aircraft park the ZNDH could now form new units: in January the 1st Group, comprising the 1st, 2nd, 3rd and 19th Squadrons was formed at Zagreb, and then the 2nd Group with the 4th, 5th and 6th squadrons and the 3rd Group with the 7th, 8th and 9th Squadrons at Sarajevo's Rajlovac airfield, whilst the 6th Group was formed at Banja Luka's Zaluzani airfield in June 1942 to cover operations in central Croatia and western Bosnia.