Negotiations with Yugoslavia for the supply of Bf –109 fighters to the Yugoslav Royal Air Force, or “Jugoslovensko kraljevsko ratno vazduhoplovstvo” (JKRV), in fact began as early as January 1938, when Yugoslav Premier Stojadinovic visited Germany with the primary purpose of acquiring modern weapons. The Yugoslav military attache in Berlin had been highly impressed by the capabilities of the Bf –109 and when he and Premier Stojadinovic met Reichsmarschall Goring to discuss planned Yugoslav weapon procurement, several dozen of Bf –109s were a priority item on the list. Goring did his best to dissuade the Yugoslav s from persisting in their demand for the Messersmith fighter, 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. The Yugoslav s remained adamant, however, and after the discussion had nearly broken down on the question of the supply of Bf –109 fighters, Goring finally relented, the iron, chrome and copper ore with which the Yugoslav s were to pay for the aircraft being of too vital importance to German industry to allow the sale to be endangered by what the Yugoslav military attache somewhat naively believed, as he was subsequently to report, a matter of principal on the part of Reichsmarschall. Nevertheless, some 15 months were too elapse before contract for the supply of Messersmith fighters to the JKRV were to be finally ratified, the RLM constantly rising minor issues to delay signature.

Finally, on April 5, 1939, and initial contract for the supply to the JKRV of 50 Bf –109Es and 25 spare DB 601 A engines was signed and 11 weeks later on June 23, supplementary contract was signed for a further batch of 50 Bf –109Es. The 6^th Fighter Regiment was designated the recipient of the German fighters and in a early autumn of 1939, the first three Bf –109E–3s were ferried from Augsburg to Zemun, Beograd. Further fighters followed in small groups in the following months, ferried by JKRV pilots (on one occasion a group that had taken –off from Frankfurt landed on a Romanian airfield as result of poor navigation), but of the 100 aircraft ordered only 73 were actually delivered and spares baking provided so inadequate that many of these were to spend much of their brief service life grounded through lack of spares, sometimes being rendered unserviceable as a result of non –availability of as simple an item as a spare tire.

The JKRV soon had cause to wonder if Goring had not, after all, been sincere in his attempt to dissuade them from acquiring the Messersmith as the 6^th Fighter Regiment began to suffer numerous lending accidents, the major problem being the JKRV s lack of suitable transition aircraft between the simple and forgiving Hawker Fury biplane and the very much more sophisticated and somewhat more mettlesome Bf-109E. An attempt was made to utilize the Bf-108B Taifyn four –seater as a transitional aircraft, but it sometimes proved necessary for former Fury pilots to convert to the more docile Hurricane for some 10 hours, following period with about 20 hours on Bf–108B before finally converting to the Messersmith fighter.

According to recorded data and sources,Yugoslav Bf -109 E pilots hit: 7 German Bf-109 E, 2 Bf-110, 4 Ju-87, 1 Ju-88, 1 He-111, 2 Do-17 and 2 Hs -126, as well as an Italian Cant Z -1007 bis. Most probably another 4 enemy aircraft were hit their type was not confirmed, though. Another 14 were severely damaged, the consequences being the fall, breaking or even destruction of the aircraft. Among those were 3 Bf-109, 2 Bf-110, 3 Ju-87, 1 Ju-88, 1 Do-17 and He -111.

During the flights over Yugoslavia (and Greece), some German fighting units, armed with Bf-109 aircraft had many losses, which caused their temporary dissolution after the end of the operations (LG 2 and II/JG 27). 87 Yugoslav pilots were ordered to units armed with Bf-109E aircraft. 57 of them were directly involved in actions (which represents 65% of the total number of operatively involved pilots). About 350 flights were accomplished, which means about 310 flights hours.

More than half of the pilots who took part in the flights, succeeded to hit the enemy once at least, some of them even twice. The Yugoslav Air Force lost all its Bf-109E aircraft in various ways: 15 German aircraft (mostly Bf-109E fighters) were hit, 15 aircraft were severely damaged, 4 others were hit on earth during enemy air force actions, 6 more were damaged in take - off or landing accidents. The most defeating data - 21 Bf-109E fighters were destroyed or burnt out on earth by their own crew, another few aircraft being lost due to various reasons, which have not been explained up to now.