Petrit Latifi
Practically nothing was known about the Serbs before 1136 when Tihomir, who was merely a shepherd, became Grand Zupan.
In the 12th century, according to a contemporary chronicler, W. of Tyre, the Serbs were “an uncultured and undisciplined people inhabiting the mountains and the forests” and who “sometimes quit their mountains and forests… to ravage the surrounding countries”, (cited by W. Miller, Essays on the Latin Orient, 1921, p. 446).
The Serbs began to gain strength in the 13th century when Stefan Simon Nemanjic – previously Zupan – started using, in 1217, the title of king. At that time the Serbs had already taken much land from the Albanians. In 1217, they conquered Peja (Pec) which was to become in 1346 the see of the Serbian Patriarch.
The greater part of Kosova, however, was not yet in their power. It was afterward that they got hold of it little by little. But the Serbian kingdom, within the short span of its existence was not marked by fixity. Its precarious stability is indicated by a striking array of capitals: Raška, Priština, Belgrade, Kruševac, Smederevo, Belgrade again, Prizren, Banjska, Shkup (Skopje), Prilep, Smederovo, Kruševac again, Kragujevac.
The names of these short-lived capitals suggest that the Serbs invaded and conquered, but then retreated and lost, because of some kind of opposition that they found. In this regard, it is interesting to note an observation made by V. Cubrilovic in his rather inhumane memorandum: “The Albanians are the only people during the last millennium that managed not only to resist the nucleus of our state, but also to harm us”. This remark indicates that the Serbs were opposed by the aboriginal population.
Considering the fact that in the 12th century the Serbs were regarded as an uncultured and undisciplined people, that they began to gain strength in the 13th century; that their kingdom lasted a little over 100 years, and Czar Dušan’s Empire merely nine, it is reasonable to assume that during this very short span of time the aboriginal population could not have been annihilated no matter how difficult the living conditions might have been for them.
As for Kosova – which is incorrectly designated as the cradle of the Nemanjic, for the Serbian nucleus did not start in Kosova, but in Raška, i.e., north of the site of present-day Novipasar – the very names of the capitals of that short-lived Serbian state suggest that Kosova was not even abidingly its center. That state, as pointed out by many historians, does not seem to have had any permanence or center.

References
https://phdn.org/archives/www.ess.uwe.ac.uk/Kosovo/juka2.htm