Boris I of Bulgaria

Boris I accepted Christianity from the Byzantine Empire, baptizing himself and his court. This act aligned Bulgaria with Christian Europe, reduced Byzantine cultural pressure, and laid the foundation for the Bulgarian Orthodox Church.

Boris I abdicated the throne to become a monk. He later returned from the monastery in 893 to depose his son Vladimir-Rasate, who had reverted to paganism, and installed his younger son Simeon I as ruler.

Boris I convened a council that replaced Greek with Old Church Slavonic as the official liturgical and literary language. This decision promoted Slavic culture and literacy, strengthening Bulgarian national identity.