By the late 1930's the threat of war hung heavy over Europe, and many nations were anxiously attempting to upgrade their armed forces. The Yugoslav government was no exception and initiated a major reequipment program for the Jugosovensko Kralievsko Ratno Vazduhoplovstvo (JKRV), the Yugoslav Royal Air Force, with the acquisition of modern aircraft such as the Bristol Blenheim 1, Savoia-Marchetti SM.79, and Dornier Do 17K bombers. Hawker Hurricanes and Messerschmitt Me 109E's were bought to reequip the fighter regiments. Indigenous aircraft such as the IK-Z were also placed into production, but in very small numbers. To guarantee supplies of aircraft and spares and to minimize the loss of precious hard currency, the government bought production licences for all of the above types with the exception of the SM.79 and the Me 109E.

Negotiations began with Bristol in the spring of 1936, even before the first flight of the production Blenheim, but the needs of the R.A.F. and the intransigence of the British Foreign Office were to delay delivery of the two pattern aircraft until November 1937 and approval of the licence for another year. Under pressure from the Yugoslav government, Ikarus began production of 40 airframes, the Mercury VIII engines being built by Bristol.

Bristol could only guarantee 50 engines due to a variety of circumstances and Ikarus frantically began searching for alternative sources. Negotiations began with PZL of Poland, but were abruptly terminated when the Germans invaded that country. Bristol suggested the Bristol Perseus engine that was licence-built by Alfa Romeo and powered the SM.79's entering service with the JKRV. In November 1939, lkarus placed an order for 100 Italian-built Perseus engines, complete with all accessories.

Ikarus was able to complete 26 Blenheim aircraft by early 1940 after begging Bristol for a few more engines. The entry of Italy into the war in June 1940 cut off the Italian supply and Ikarus reopened negotiations with the German-controlled PZL factory and received enough engines to finish the remaining 16 aircraft by the middle of 1940.

Concerned by the slow delivery of Blenheims by Ikarus, the JKRV pressed for aircraft to be supplied direct from Britain. After the first request for 40 Blenheim 4's was refused, agreement was reached in August 1939 on the supply of 20 new Blenheim 1's which were delivered in February and March by air.

After the request for a licence to build 50 Blenheim 4's and to buy 100 Mercury XV engines was denied, Ikarus began construction of a further 20 aircraft that were to have a long nose based on that of the Blenheim 4 and much improved armament with additional 7.7mm Browning machine guns in the nose and the ventral hatch and with the Browning in the turret replaced by a Breda 12.7mm machine gun.

Further negotiations with the Germans resulted in the supply of 42 more engines to power the aircraft. After the conquest of Yugoslavia, the 20 incomplete airframes were sold to Finland and used in the production of Blenheim 4's.

The Yugoslav government had begun to attach a high degree of urgency to the reequipment and expansion of the JKRV by mid-1938. The Italians offered rapid delivery as an incentive to purchase SM.79's. Thirty were delivered in late 1938 by the diversion of the aircraft that were to reequip 10 Stormi at Bresso. The remaining 15 aircraft were delivered during September-October 1939.

The JKRV was very impressed by the performance of the Do 17M V1 at the Dubendorf International Flying Meeting of July 1937, where it was faster than every fighter present and easily won the "Circuit of the Alps". An order for 36 Do 17K's and a licence for a further 100 was arranged very quickly in light of Germany's desperate need for foreign exchange and the first of 20 Do 17Ka-1's was delivered on 25 October 1937. The Ka-1 and the Ka-2 versions were based on the Do 17E airframe with the Ka-1 used as a bomber and the Ka-2 optimized for long-range reconnaissance with only a secondary bombing capability.

Two Do 17 Kb-1 bombers were delivered as pattern aircraft, finishing the German contract, and were based on the Do 17M with improved payload and range over the Ka-1 bombers. The Do 17K's were true mongrel aircraft with their German-built airframes powered by French Gnome-Rhone 114Na engines, armed with three Belgian machine guns, and equipped with Yugoslav bomb racks and bombsight. Yugoslav production of the Do 170-11 began in 1939 with deliveries commencing from early 1940. Only 36 or so aircraft had been finished by April 1941 as production of the engines was unable to keep pace with airframe deliveries. Thus only a total of 70 of these aircraft were in service on 6 April 1941 when the Germans struck.

24 Hurricane 1's were bought from Britain in 2 batches with deliveries of the first batch commencing on 15 December 1938 and the second in February 1940 along with a licence to build them in Yugoslavia. Orders were placed for 60 aircraft by the Zmaj factory and an additional 40 by Rogozarski, with production expected to reach 8 a month from each factory by mid-1941. At any rate, Zmaj had produced only 20 aircraft by the time Yugoslavia was overrun.

In an interesting experiment, the Yugoslavs mounted a DB 601A engine from a Me 109E in a Hurricane as a part of a program to evaluate new engines for the IK-Z fighter. This hybrid could outclimb both the Hurricane and the Me 109E and was only slightly slower than the latter.

Negotiations began with the Germans as early as January 1938 over the supply of Me 109's. Goring tried to dissuade the Yugoslavs, commenting "There is too much with which your pilots are unfamiliar in this new aircraft. They should convert by degrees to such fast warplanes or they will suffer many casualties, particularly during landings, and will develop a fear of really advanced fighters." Nevertheless, the Yugoslavs persisted and eventually signed a contract for 50 Me 109E's and 25 spare engines on 5 April 1939. A supplementary contract was signed in June for another 50 aircraft. They were to be paid for by deliveries of raw materials.

Deliveries began in the early autumn of 1939, but only 73 had actually been delivered by April 1941. The provision of spares proved to be grossly inadequate and the Me 109s spent most of the time grounded. The Me 109, with its difficult ground-handling characteristics, proved Goring correct, as many Yugoslav pilots had a difficult time converting from the forgiving Fury biplane. Some pilots had to spend 10 hours on the more docile Hurricane, then 20 hours on the Me 108 liaison plane, before transitioning on to the Me 109.

The Yugoslavs had a very competent indigenous aircraft design and manufacturing capability as exemplified by the Ikarus IK-2 and IK-Z fighters. The IK-2 was a high-wing monoplane powered by a 920 hp Hispano-Suiza 12Ycrs engine with an armament of a 20mm cannon and 2 x 7.92mm Browning machine guns.Eight survivors of the twelve ordered were in service when the Germans invaded. The IK-Z was a low-wing monoplane with a retractable undercarriage that had the same engine and armament as the IK-2. Despite the low-powered engine, the IK-Z was as fast as the Hurricane and more maneuverable than either the Me 109 or the Hurricane, but was shorter-ranged. The initial order for 12 had been completed by April 1941, but after the Rogozarski factory finished its 40 Hurricanes it was to build another 25 IK-Z's. Four were in overhaul when the Germans attacked. A Merlin engine had been installed in another IK-Z for tests designed to check the suitability of the IK-Z airframe for more powerful engines (as the H-S 12Y-51 engines of 1,100 hp planned for the second batch had become unavailable when France fell), but this had not flown by the time the Germans invaded.

The Yugoslavs were working on several new aircraft designs when they were overrun. These included the IK-5, a twin-engined fighter that was to be built in two versions, a single-seat interceptor and a two-seat destroyer. Construction of the prototype had just begun by April 1941. There was a program for a fast attack bomber that had three competitors: the Ikarus Orkan, Rogozarski R-313 and the Zmaj R-1. The prototype Orkan was powered by two 840 hp Fiat A 74 RC 38 engines that produced an estimated top speed of 342 mph with a range of 1394 miles without any armament. This was truly outstanding performance from a plane powered by such low-powered engines (although performance of the production versions would have suffered, due to the additional weight of armaments and radios). It had a planned maximum bomb-load of 1764 pounds with a forward-firing armament of 2 x 20mm cannon and 2 x 12.7mm Breda machine guns with 1 x 20mm cannon in the dorsal position and a 7.92mm Darne machine gun firing through a ventral hatch.

The Rogozarski R-313 prototype was of all wooden construction and was powered by two Walter Sagitta I-SR engines of 500 hp and was delivered in early 1940. It carried 882 lbs. of bombs and was armed with a 20mm cannon in the nose and a dorsal 8mm Browning. Maximum speed of the prototype was 286 mph and the range was some 800 miles. A decision to power the production R-313's with either the Merlin or the DB 601 had not been made by the time of the German invasion. The prototype crashed at Niksic airfield when it was taking off to escape to Greece. I'm still trying to locate information on the R-1, but I'm certain that the prototype was never finished. [See Chart at end]

Europa OB:

Apr I 40
1 x Fury 2F2 0/5
1 x Me 109E7F5 1/7
1 x Hurri 1 5F5 0/8
1 x Do 17Ka 31331-1/19
1 x Bien 1 31331-1/20
1 x SM.79 21331-2/21
1 x Do 22K 1S2 1/25
Group Allowance: 7

Nov I 41:
1 x Hurri 1 5F5 0/8

Jan I 42:
1 x Do 171(b 4133 2-2/17
GA increase: +1;

Battle History