The south of Russia was blessed with the work of Ss. [[Cyril and Methodius]] [[Equal-to-the-Apostles]], the [[Illuminator]]s of the Slavs. Although their work was around 863 in Moravia (roughly equivalent to the modern [[Church of the Czech Lands and Slovakia|Slovakia]]), the benefit was to all the Slavic lands (particularly [[Church of Bulgaria|Bulgaria]], [[Church of Serbia|Serbia]], and Russia).

They not only brought Christianity in a common language, they brought Byzantium. The Slavs received a fully articulated system of Christian doctrine and a fully developed Christian civilization. The age of the [[Ecumenical Councils|Seven Councils]] was complete and the doctrines of the [[Trinity]] and the [[Incarnation]] had already been worked out. Because people were preached to in their own tongue, and of taking services in Slavonic, they truly could make Christianity their own.