[4] After Mutimir (his grandfather) died in 891, Pribislav succeeded as prince, and ruled briefly for a year till Petar returned and defeated him.
[7] In 917, a Byzantine army led by Leo Phokas invaded Bulgaria but was decisively defeated at the Battle of Achelous on 20 August 917.
[8] After the Achelous,[6] Symeon sent an army to Serbia led by Pavle (after he had heard of a Byzantine–Serbian alliance), to take the Serbian throne, however, unsuccessfully as Petar proved a good opponent.
Symeon then sent generals Marmais and Theodore Sigritsa, persuading Petar (through an oath) to come out and meet them, then captured and took him to Bulgaria where he was put in prison, dying within a year.
In the meantime, Pavle switched his allegiance back to the Byzantines, prompting Symeon to dispatch Zaharija against him at the head of a Bulgarian army in 921.