De Administrando Imperio in the context of "Constantine VII"

Principality of Serbia (Modern Serbian: Кнежевина Србија / Kneževina Srbija; also known as Principality of Serbs, (Modern Serbian: Кнежевина Срба / Kneževina Srba; Latin: Principatum Serborum; Modern Greek: Πριγκιπάτο της Σερβίας) was one of the early medieval states of the Serbs, located in the western regions of Southeastern Europe. It existed from the 8th century up to c. 969–971 and was ruled by the Vlastimirović dynasty. Its first ruler known by name was Višeslav, who started ruling around 780, while by that time (starting from the years 680–681), the Bulgarian state had taken the lands to the east. Vlastimir resisted and defeated the Bulgarian army in a three-year-war (839–842), and the two powers lived in peace for some decades. Vlastimir's three sons succeeded in ruling Serbia together, although for a limited time; Serbia became a key part in the power struggle between the Byzantines and Bulgarians, predominantly allied with the Byzantines, which also resulted in major dynastic wars for a period of three decades. The principality was annexed in 924 by Simeon I and subjected to Bulgarian rule until 933 when Serbian prince Časlav was established as ruler of the Serbian land, becoming the most powerful ruler of the Vlastimirović dynasty.

An important process during this period was the Christianization of the Serbs, completed by the establishment of Christianity as state-religion in the second half of the 9th century. The principality was annexed by the Byzantines in c. 969–971 and ruled as the Catepanate of Ras. The main information of the history of the principality and Vlastimirović dynasty are recorded in the contemporary historical work De Administrando Imperio (written c. 948–949).

The history of Bosnia and Herzegovina in the Middle Ages refers to the time period between the Roman era and the 15th-century Ottoman conquest. The Early Middle Ages in the Western Balkans saw the region reconquered from barbarians (Ostrogoths) by the Byzantine Emperor Justinian I (r. 527–565), followed by raids and migrations carried out by Slavic peoples in the 6th and 7th centuries. The first mention of a distinct Bosnian region comes from the 10th-century Byzantine text De Administrando Imperio. By the late 9th and early 10th century, Latin priests had Christianized much of Bosnia, with some areas remaining unconverted. In the High Middle Ages, Bosnia experienced economic stability and peace under the Ban Kulin who ruled over Banate of Bosnia from 1180 to 1204 and strengthened its ties with the Republic of Ragusa and with Venice. The Kingdom of Bosnia emerged in the Late Middle Ages (1377). The kingdom faced internal and external conflicts, eventually falling under Ottoman rule in the late 15th and early 16th centuries.

The Belojević clan (Serbian Cyrillic: Белојевић), colloquially Travunian dynasty, was a local Slavic ruling clan from region surrounding Trebinje, a center of an early Slavic polity, Travunia. The clan was in vassal relations with the first Serbian Principality's ruling Vlastimirović's, but constantly strived for independence starting with the clan's progenitor Beloje, who sought to free himself of Serbian rule. Beloje was mentioned as the župan of Travunia in the chapter on the Serbs in De Administrando Imperio (DAI) of Byzantine Emperor Constantine VII (r. 945–959). Prince Vlastimir (r. 836–851) married his daughter to Beloje's son Krajina, and elevated him to the rank of archon, sometime prior the Bulgar–Serb War (839–842). Krajina's descendants were entitled to rule the region comprising the hinterland of Dubrovnik and Boka Kotorska, with seat at Trebinje, still under Serbian suzerainty. The clan is later mentioned in the semi-mythical Chronicle of the Priest of Duklja, which mentioned that a descendant of Hvalimir, Dragomir, ruled Travunia in the second half of the 10th century, his brother Petrislav ruling Duklja and his son Stefan Vojislav later ruling Duklja and founding the Vojislavljević dynasty.

Višeslav (Serbian Cyrillic: Вишеслав) or Vojislav (Serbian Cyrillic: Војислав), from Boïsesthlabos (Greek: Βοϊσέσθλαβος), was a Serbian ruler and the first known by name, who ruled in c. 780. Serbia was a Slavic principality, subject to the Byzantine Empire, located in the western Balkans, bordering with Bulgaria in the east. Mentioned in the De Administrando Imperio (DAI) from the mid-10th century, Višeslav was a progenitor of the Serbian ruling family, known in historiography as the Vlastimirović dynasty. He was descended from the unnamed Serbian prince who led his people to the Dalmatia province and established hereditary rule under Byzantine suzerainty. The names of Višeslav's predecessors were not included in the DAI. The dynasty ruled the Principality of Serbia from the early 8th century until around 960.

In 926 a battle was fought in the Bosnian highlands between the armies of the Bulgarian Empire, under the rule of Bulgarian Tsar Simeon I, who at the time also fought a war with the Byzantine Empire, and the Kingdom of Croatia under Tomislav, the first king of the Croatian state. The battle is also known as the Battle of the Bosnian Highlands (Bulgarian: Битка при Босненските планини, Croatian: Bitka na Bosanskim visoravnima). It was fought in the Dinaric Alps of Eastern Bosnia near the rivers Bosna and Drina, the border area between the Kingdom of Croatia and the Bulgarian Empire.

Principal information on the battle is provided by the emperor Constantine VII of the Byzantine Empire in his work De Administrando Imperio ("On the Governance of the Empire") and in the collection of preserved historical writings called Theophanes Continuatus. Simeon's aim was to defeat the Byzantine Empire and conquer Constantinople. To achieve his aim, Simeon overran the eastern and central Balkans several times, occupied Serbia and finally attacked Croatia. The result of the battle was an overwhelming Croatian victory.

Beloje (Serbian Cyrillic: Белоје; Greek: Βελάης; fl. 839), was a local Slavic chieftain from the region surrounding Trebinje, who ruled the area with a title of župan, sometime in the first half of the 9th century. Travunia was a polity centered in Trebinje (now in southern Bosnia and Herzegovina), and at the time subject to the Principality of Serbia. Mentioned in De Administrando Imperio (DAI) of Byzantine Emperor Constantine VII (r. 945–959), Beloje was a contemporary of Serbian ruler Vlastimir (r. 836–851). It is unknown how he came to the position; it might have been through the primogeniture principles, however, there is no definite answer. Vlastimir married his daughter to Beloje's son Krajina, and "desiring to ennoble his son-in-law", elevated his rank to archon (prince) and made him independent. Travunia was thus elevated from a župa into an archonty (principality), practically independent, while Vlastimir oversaw his son-in-law. T. Živković theorized that Beloje sought to free himself of Serbian rule, and that Vlastimir prevented this through a political marriage between the two families, possibly prior to the Bulgar–Serb War (839–842). Krajina's descendants were entitled the rule of Travunia under Serbian suzerainty.

There is a hypothesis that the legendary king Pavlimir Belo (or Belimir) mentioned in the Chronicle of the Priest of Duklja (CPD) was supposedly based on Beloje. The CPD is a primary source dating to ca. 1300–10 largely discredited in historiography (events in the Early Middle Ages deemed useless). The CPD mentions this individual, Belo, as being born as Pavlimir, receiving his nickname from his relatives and other Romans from bello, "because he very much loved war". The legend of Pavlimir-Belo continues with his stint at Syrmia, where he defeated the Syrmians and Hungarians, and his defeat of Rascian župan Ljutomir. Belo is mentioned in the CPD as a Rascian župan, while DAI mentions Beloje as a Travunian župan. N. Banašević noted that while the two names were similar, they were not identical.

In the first half of the 7th century, there was a ruler of the Serbs who led half of the Serbs from their homeland (White Serbia) to settle in the Balkans during the reign of Byzantine Emperor Heraclius (610–641), as mentioned in Emperor Constantine VII's work De Administrando Imperio (10th century). The work does not record his name, but states that he was the progenitor of the first Serbian dynasty, known in historiography as the Vlastimirović dynasty.

Historians have variously referenced this person as 'unknown archon' or 'unnamed Serbian archon' (Serbian: Непознати архонт / неименовани српски архонт, Nepoznati arhont / neimenovani srpski arhont), with the title of archon usually translated as a ruler or prince or knez.