Braničevci and Timočani, together with other tribes of the frontier, revolted and seceded from Omurtag's Bulgaria because of an administrative reform that deprived them of much of their local authority. They left the association (societas) of the Bulgarian Empire and sought, together with many other Slavic tribes, protection from Holy Roman EmperorLouis the Pious, meeting him at his court at Herstal.
Ljudevit Posavski leads an uprising against the Franks (819). According to the Royal Frankish Annals, (written 822), Ljudevit went from his seat in Sisak to the Serbs somewhere in western Bosnia – the Serbs are mentioned as controlling the greater part of Dalmatia ("Sorabos, quae natio magnam Dalmatiae partem obtinere dicitur").
Radoslav is succeeded by his son Prosigoj.
Braničevci and Timočani and other frontier tribes come under Frankish rule.
Timok and Branicevo would be of dispute between the Franks and Bulgars, the Khan sent embassies in 824 and 826 seeking to settle the border dispute, but was neglected. The Bulgarian Empire subsequently annex the region again.
Omurtag invades Frankish Croatia using boats sailing from the Danube up the Drave, spreading destruction. The Slavs and other tribes on its banks were cowed into submission, and agreed to accept Bulgar governors.
It is thought that the rapid extension of Bulgars over Slavs to the south prompted the Serbs to unite into a state under Vlastimir.
Vlastimir united several Serbian tribes, and Emperor Theophilos (r. 829–842) probably granted the Serbs independence, thus the Serbs acknowledged nominal overlordship of the Emperor.
In c. 839 Doge of VenicePietro Tradonico headed with a large fleet towards the Narentines. They subsequently made peace and renewed a treaty, that would stop the piracy against the Republic of Venice. They however, shortly thereafter, plundered the Venetian borders under the leadership of Uneslav and Diodor.Ljudislav, the Narentine ruler that defeated Doge Pietro in 840, was possibly a co-ruler or successor of Drosaico.
KhanPresian I of Bulgaria (r. 836–852) invades Serbian territory between 839–842 (see Bulgarian–Serbian Wars). The invasion led to a 3-year war, Vlastimir was victorious; Khan Presian made no territorial gain, was heavily defeated and lost many of his men as the Serbs had a tactival advantage in the hills, Presian was driven out by the army of Vlastimir. The war ended with the death of Theophilos in 842, which released Vlastimir from his obligations to the Byzantine Empire.
Soon after 846, with the end of the Thirty Years’ truce, Malamir (or Presian) invaded the regions of the Struma and the Nestos, Empress-Regent Theodora answered by attacking Thracian Bulgaria. A brief peace was concluded, then Malamir proceeded to invade Macedonia. The Bulgarians soon annexed Ohrid, Bitola and Devol.
The Bulgar Army led by Vladimir, the son of Boris I of Bulgaria, invaded Serbia in an attempt for vengeance for the previous defeat of Presian 839–842 against Vlastimir. The Serbian Army was led by Mutimir and his brothers, which defeated the Bulgars, capturing Vladimir and 12 boyars. Boris I and Mutimir agreed on peace (and perhaps an alliance), and Mutimir sent his sons Pribislav and Stefan to the border to escort the prisoners, where they exchanged items as a sign of peace, Boris himself gave them "rich gifts", while he was given "two slaves, two falcons, two dogs, and 80 furs".
An internal conflict among the dynastic brothers resulted in Mutimir banishing the two younger brothers to the Bulgarian court. He kept Petar in his court, for political reasons. Petar soon fled to Croatia. The reason of the feud is not known, however, it is postulated that it was a result of treachery.
The seal of Strojimir (died between 880–896), the brother of Mutimir, was bought by the Serbian state in an auction in Germany. The seal has a Patriarchal cross in the center and Greek inscriptions that say: "God, help Strojimir (CTPOHMIP)".
^ abDe Administrando Imperio, ch. 29 [Of Dalmatia and of the adjacent nations in it]: "...the majority of these Slavs [Serbs, Croats] were not even baptized, and remained unbaptized for long enough. But in the time of Basil, the Christ-loving emperor, they sent diplomatic agents, begging and praying him that those of them who were unbaptized might receive baptism and that they might be, as they had originally been, subject to the empire of the Romans; and that glorious emperor, of blessed memory, gave ear to them and sent out an imperial agent and priests with him and baptized all of them that were unbaptized of the aforesaid nations..."