ボリス1世
The Christianization of Bulgaria was the process by which 9th-century medieval Bulgaria converted to Christianity. It reflected the need of unity within the religiously divided Bulgarian state as well as the need for equal acceptance on the international stage in Christian Europe. This process was characterized by the shifting political alliances of Boris I of Bulgaria (ruled 852-889) with the kingdom of the East Franks and with the Byzantine Empire, as well as his diplomatic correspondence with the Pope.