PrologueDuklja, Podgorica, Montenegro
According to the De Administrando Imperio, the Serbs settled the Balkans under the protection of Byzantine Emperor Heraclius (r. 610–41), and were ruled by a dynasty known in historiography as the Vlastimirović dynasty. Slavs had begun settling the region in the early 6th century, after raiding deep into the Empire. They settled "baptized Serbia", which included Bosnia, and the maritime lands of Travunija, Zahumlje and Paganija, while maritime Duklja was held by the Byzantines, it was presumably settled with Serbs as well. All of the maritime lands bordered "baptized Serbia" to the north.
In the mid-9th century, the hitherto peaceful neighbour of Bulgaria invaded but was defeated in war. Serbia was Christianized in ca. 870, although missions had been made during Heraclius' reign. In the following decades, members of the dynasty fought succession wars, and Serbia became a matter of Byzantine-Bulgarian rivalry. The written information regarding the dynasty ends with the DAI and Prince Časlav's death (ca. 950), after which the realm crumbled into pieces.
Meanwhile, Duklja emerged as the dominant Serbian principality, that gradually also including Travunija, Zahumlje, Bosnia and Raška. Initially a vassal of the Byzantine Empire, Stefan Vojislav (1034–1043) rose up and managed to take over the territories of the earlier Serbian principality, founding the Vojislavljević dynasty. Between 1043 and 1080, under Mihailo Vojislavljević (r. 1050–1081), and his son, Constantine Bodin (r. 1081–1101), Duklja saw its apogee. Mihailo was given the nominal title King of Slavs by the Pope after having left the Byzantine camp and supported a Slavic uprising in the Balkans, in which his son Bodin played a central part. Having incorporated the Serbian hinterland and installed vassal rulers there, it emerged as the most powerful Serb polity, seen in the titles used by its rulers ("Prince of Serbia", "of Serbs"). However, its rise was short-lived, as Bodin was defeated by the Byzantines and imprisoned; pushed to the background, his relative and vassal Vukan became independent in Raška, which continued the fight against the Byzantines while Duklja was struck with civil wars.