Noel Malcolm writes:

“Medieval Kosovo is often referred to in general terms as ‘the cradle of the Serbs’, as if it had been a Serb heartland from the outset; but the reality was rather different. Just over 800 years separate the arrival of the Serbs in the Balkans in the seventh century from the final Ottoman conquest in the 1450s: out of those eight centuries, kosovo was Serb-ruled for only the last two-and-a-half – less than one third of the entire period. Bulgarian khans or tsars held Kosovo from the 850s until the early eleventh century, and Byzantine Emperors until the final decades of the twelfth.”

Sources

Chapter 3 in Noel Malcolm’s Kosovo, a short history (Macmilan, London, 1998, p. 22-40)