Revolts and Incursions
The initial successes of Petar's reign were followed by several minor setbacks. Around 930, Petar faced a revolt led by his younger brother Ivan, who was defeated and sent into exile in Byzantium. Soon afterwards Peter's older brother Michael escaped from his monastery and led a more formidable rebellion, which terminated with his early death. The youngest brother, Benjamin (also called Bojan), was accused of being a werewolf and magician by the Italian Bishop Liutprand of Cremona, but apparently posed no threat to Peter's authority.
Perhaps taking advantage of these challenges to Petar's rule, the Prince of Serbia Časlav Klonimirović escaped the Bulgarian capital Preslav in 933 and, with tacit Byzantine support, managed to raise a Serbian revolt against Bulgarian rule. The revolt succeeded, and Serbia recovered its independence. Peter may have had to also face the incursions of the Magyars, who had been defeated and forced into Pannonia by his father in 896. Perhaps after an initial defeat, Petar came to terms with the enemy, and now utilized Magyar groups as his allies against Serbia. Various Magyar clans and chieftains appear to have begun to settle in what was still Bulgarian territory north of the Danube, where they may have become Bulgarian federates, enjoying independence from the Árpád dynasty. This arrangement paved the way for the eventual loss of the region to the Magyars, although that happened over the half-century following Petar's death. Petar apparently allowed these groups to cross Bulgaria and raid Byzantine territories in Thrace and Macedonia, perhaps as an underhanded reaction against Byzantine support for the Serbian rebellion.
Read more about this topic: Peter I Of Bulgaria