Cyril and Methodius brought literacy to the Slavic world by creating an alphabet for the Slavic language. It was based on their own Greek alphabet and is the ancestor of the Cyrillic alphabet.
They arrived in Greater Moravia in 863 AD and although they left after three years, they continued their work to codify Slavonic as another liturgical language alongside Latin. Cyril, (Constantine) died in 869 in Rome but Methodius returned to Greater Moravia as a teacher and was later pronounced Pannonian Archbishop. After his death in 885 AD, the Latin clergy gradually became the decisive power in the empire and the successors of Methodius were exiled mostly to the historical territories of Bulgaria.Some important literature, especially Old Testament Pseudepigrapha, is preserved in Old Church Slavonic.
Background here and here and links. For other posts on Church Slavonic and Slavonic Pseudepigrapha, start here and follow the links.
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