A son of the Bulgarian Khan Presian, he was instructed in the faith by St Photios, Patriarch of Constantinople. He labored throughout his reign to establish and spread the Christian faith in Bulgaria. When the disciples of Ss Cyril and Methodius were driven from Moravia and came to Bulgaria, he greatly assisted them in their missionary work there. He retired to a monastery, leaving rule of his country in the hands of his son Vladimir. But when he learned that Vladimir was persecuting Christians and trying to re-establish paganism, he left the monastery, took up the sword, overthrew his son, put his younger son Symeon on the throne and, when he was confident that the country was again in Christian hands, returned to the monastery, where he ended his life in peace and piety.