Principality of Serbia (early medieval)

The Principality of Serbia was an early medieval Serbian state in the western Balkans, ruled from the eighth century by the Vlastimirović dynasty. The first named ruler, Višeslav, began his reign around 780. Prince Vlastimir defeated the Bulgarian army in a three-year war between 839 and 842, and the Serbs later became a key factor in the Byzantine-Bulgarian struggle; after his death the lands were divided among his sons and repeatedly contested by both empires. After a period of Bulgarian annexation and internal strife, Prince Časlav reunited the Serbian lands in the 930s and became the dynasty's most powerful ruler. Christianity became the state religion in the second half of the ninth century, and the Ras bishopric was established. The principality was annexed by Byzantium around 969–971 and reorganized as the Catepanate of Ras. Most of what is known comes from Constantine VII Porphyrogenitus's De Administrando Imperio, written around 948–949. Its core lay in Raška, with Stari Ras as the principal seat.