Boris I of Bulgaria

Boris I ruled the First Bulgarian Empire from 852 to 889, a stretch marked less by battlefield wins than by calculated moves at the crossroads of Rome and Constantinople. In 864 he abolished paganism and Christianized Bulgaria, then played the Patriarchate against the Papacy to win an autocephalous church - blocking Byzantine meddling in Bulgarian affairs. When disciples of Cyril and Methodius were expelled from Great Moravia in 885, he gave them sanctuary, preserving the Glagolitic script and seeding what became Cyrillic and Slavic literary tradition. He abdicated in 889, but his eldest son attempted a pagan restoration; Boris came back, deposed him, and convened the Council of Preslav, which replaced Byzantine clergy with Bulgarians and Greek liturgy with Old Church Slavonic. He died May 2, 907, venerated as Saint Boris the Baptizer and Equal-to-the-Apostles.