The official history of Bulgarian Orthodox Church begins with the Conversion of the Bulgarians by Prince Boris in 864. In the next five years he takes active measures to set up an independent Bulgarian Church. The appearance of an independent Bulgarian Church goes through the long way of the dissemination of Christian faith among the Bulgarians, the building of churches and the setting up of bishoprics. A major event in strengthening the positions of the Bulgarian Church is its nationalisation after 885, when the disciples of the holy brothers Cyril and Methodius introduce church service in Old Bulgarian. The seat of the archbishop moves from Pliska to the new capital Preslav.
New bishops appear, the number of monasteries in towns and in the country grows considerably.
The internal autonomy of the Bulgarian Orthodox Church grows and with it grows its international authority. In 927 Byzantium recognises the royal title of Peter . Not long after that the Bulgarian kingdom has its autocephalous church, headed by a patriarch. The first to bear this title is Damyan . Its foundation introduces a new element in the century-old principle of the church pentarchy.