Cyril and Methodius, brothers born in Thessalonika, are honored as apostles to the southern Slavs and as the founders of Slavic literary culture. Cyril was a philosopher and a deacon, who eventually became a monastic missionary. Methodius was first the governor of a Slavic colony who subsequently turned to the monastic life, and later served as both abbot and bishop.

In 862, the King of Moravia asked for missionaries who would teach his people …