The name Boris in Bulgaria is very common — in etymology it goes back to the Old Turkic bjori — wolf, or to the Altai leopard — tiger. Unlike Russia, where the name is associated primarily with the names of the holy noble princes Boris and Gleb, south of the Danube it is associated with the Bulgarian prince Boris the First Michael. The Bulgarian Church accepts him as an Equal-to-the-Apostles saint, since it was he who converted to Christianity and also contributed to the approval of the new Slavic letter.
Prince Boris ruled Bulgaria from 852 to 889. This time can be called truly a turning point. Even at the beginning of his reign, the son of Khan Persian felt the need for even greater consolidation of Bulgarian, Thracian and Slavic tribes in the Balkans. The military treaty against the common enemy — Byzantium — between the Slavs and the ancient Bulgarians of the Asparukh era has already begun to become obsolete. The cultural and political flourishing of Second Rome promised bleak prospects for the Bulgarian Khanate. Many people began to convert to Christianity. Boris's sister also became a Christian. In a situation where both related tribes north of the Black Sea — Khazars and Volga Bulgarians — found hope in Judaism and Islam, the Bulgarian ruler decided to convert to Christianity.
First, Boris began to look for rapprochement with the Roman Catholic Church. Pope Nicholas the First was sent a list with 105 questions designed to cover issues of faith. The matter was almost resolved when the new pope, Adrian II, who replaced Nicholas, who died in 867, unexpectedly refused Boris the appointment of Cardinal Formosa of Porto as head of the Bulgarian church.
The contradictions that arose led to the convening of an extraordinary meeting during the Eighth Ecumenical Council (869—870), at which it was decided that the Bulgarian church would be organized according to the Byzantine model. In the end, Boris liked this. Having adopted his new Christian name Michael – during his solemn baptism in Constantinople, he had the opportunity to influence the decisions of the patriarch with his power. Since 879, Constantinople completely declared the Bulgarian church autocephalous, which further strengthened the position of the prince.
The end of the 9th century was marked by another major event. Boris the First received the students Cyril and Methodius — Naum, Angelarius and Clement —, expelled from Great Moravia, and provided them with excellent conditions for the development of their cause. The created two — book schools in Ohrid (present-day Macedonia) and in the Bulgarian capital Pliska — laid the foundations for the cultural flourishing of Bulgaria.
Long before the Reformation, church services in the Balkans began to be conducted in an understandable Church Slavonic language. What Konstantin-Kirill dreamed of — the destruction of the tri-lingual model and the achievement of the Christian faith to the heart of any believer in his native language — came true. All conditions were created not only for the consolidation of the broad masses of the people on the basis of a new faith and living Slavic writing, but also for the future cultural influence on the Eastern Slavs. The Golden Age of Bulgaria has arrived.