It was populated by Slavs as early as the 6th century. By the late 7th century, a group of Bulgars under Kuber settled in the area and in neighbouring Macedonia. In 842, during the reign of Khan Presian I, the region became part of the First Bulgarian Empire. During the Christianization of Bulgaria under Presian's son Boris I, Kutmichevitsa became one of the two most important cultural centers of Bulgaria, the other being the original core of the Bulgarian state around Pliska and Preslav. The Ohrid Literary School produced many works important for the Medieval Bulgarian literature as well as for all the Slavic peoples. Kutmichevitsa (or Devol) was probably one of the 10 comitati (administrative regions) of the Bulgarian Empire, with Devol/Deabolis as its capital which also served as a seat of the diocese of the name. Other important towns included Glavinitsa (Ballsh), Belgrad/Velegrada (Berat) and Chernik. Kutmichevitsa remained in Bulgaria until the fall of the empire under Byzantine rule by the armies of Basil II in 1018. The last ruler of the First Empire, Presian II, made his final desperate stand in that region, in the mountain Tomoritsa (Tomorr). By 1019 the Byzantines captured the last Bulgarian strongholds in Kutmichevitsa.