It is thought that the rapid extension of Bulgars over Slavs to the south prompted the Serbs to unite into a state. It is known that the Serbs and Bulgars lived in peace until the invasion in 839. Vlastimir united several Serbian tribes, Emperor Theophilos probably granted the Serbs independence, and they acknowledged nominal overlordship of the Emperor. The annexation of western Macedonia by the Bulgars changed the political situation, Malamir or Presian may have seen a threat in the Serb consolidation, and opted to include them in their conquest of Slav lands. KhanPresian I of Bulgaria invades Serbian territory between 839-842. The Bulgars may have been threatened by the Serbs, or, perhaps, the Byzantines wanted to divert Bulgarian attention so that they could cope with the Slavic uprising in the Peloponnese. The invasion led to a 3-year war, from which Vlastimir emerged victorious; the heavily defeated Khan Presian made no territorial gains, lost many of his men, and was driven out by Vlastimir's army. The war ended with the death of Theophilos in 842, which released Vlastimir from his obligations to the Byzantine Empire, but also gave the Bulgarians the opportunity to annex the areas of Ohrid, Bitola and Devol in 842–843. Vlastimir continued expanding to the west, taking southeast Bosnia and northeast Herzegovina. In the meantime, Braničevo, Morava, Timok, Vardar and Podrimlje were occupied by the Bulgars.
Life
Vlastimir died sometime between 845 and 850 and his rule was divided among his three sons: Mutimir, Strojimir and Gojnik. Although they ruled in an oligarchy, Mutimir had the supreme rule, and the two brothers acted as vassals to him. In 853 or 854, the Bulgar Army, led by Vladimir, the son of Boris I of Bulgaria, invaded Serbia in an attempt to exact vengeance for the previous defeat. The Serbian Army was led by Mutimir and his brothers, which defeated the Bulgars, capturing Vladimir and 12 boyars. Boris I and Mutimir agreed to cease hostilities, and Mutimir sent his sons Bran and Stefan to the border to escort the prisoners, where they exchanged items as a sign of peace. Boris gave them "rich gifts", while he was given "two slaves, two falcons, two dogs, and 80 furs". An internal conflict among the brothers resulted in Mutimir banishing the two younger brothers to the Bulgarian court. He, however, kept the son of Gojnik, Petar, in his court for political reasons. Petar soon fled to Croatia. The reason for the feud is not known, although it is hypothesized that it was the result of treachery. Mutimir sent envoys to Byzantine Emperor Basil I, asking him to baptize the lands. He put Serbia under the suzerainty of the Byzantine Empire. The SaracensattackedRagusa in 866. The Ragusians asked Basil I for help, which he answered, sending a large fleet with his admiralNiketas Ooryphas. The pagan Narentines sacked a ship with emissaries returning from Constantinople, which enraged Basil I, resulting in him sending a fleet and subsequently subduing them. By 878, all of Dalmatia was under Byzantine rule, and most of the land was under the religious jurisdiction of the Ecumenical Patriarchate of Constantinople. Mutimir died in 891 and was succeeded by his eldest son, Pribislav. He was most likely buried in the Church of Peter and Paul at Ras, as was Petar.
Christianization
The Serbs were baptized by Constantinopolitan missionaries sent by Basil I, after Mutimir had acknowledged Byzantine suzerainty. Basil may have also sent a bishop. The Christianization was due partly to Byzantine and subsequent Bulgarian influence. It is important to note that at least during the rule of Kotsel of Pannonia, communications between Serbia and Great Moravia must have been possible. The pope was presumably aware of this fact when planning Methodios' diocese, as well as the fact that the Dalmatian coast was in Byzantine hands as far north as Split. There is a possibility that some Cyrillomethodian pupils reached Serbia in the 870s, perhaps even sent by Methodius himself. Serbia is accounted Christian as of about 870. The lasting Christian identity is evident in the tradition of theophoric names in the next generation of Serb royalty: Petar Gojniković, Stefan Mutimirović and Pavle Branović. Petros and Stephanos are both characteristically Byzantine. The first Serbian bishopric was founded at the political center at Ras, near modern Novi Pazar on the Ibar river. The initial affiliation is uncertain; it may have been under the subordination of either Split or Durazzo, both then Byzantine. The early church of Saint Apostles Peter and Paul at Ras, can be dated to the 9th–10th century, with the rotunda plan characteristic of first court chapels. The bishopric was established shortly after 871, during the rule of Mutimir, and was part of the general plan of establishing bishoprics in the Slav lands of the Empire, confirmed by the Council of Constantinople in 879–880. The Eparchy of Braničevo was founded in 878. Mutimir maintained the communion with the Eastern Orthodox Patriarchate of Constantinople when Pope John VIII invited him to recognize the jurisdiction of the bishopric of Sirmium in a letter dated to May 873. The Serbs and Bulgarians subsequently adopted the Old Slavonic liturgy instead of the Greek.
Legacy
In the , about the life of Boris I of Bulgaria, the peace treaty between Mutimir and Boris I is featured.
