Cyril and Methodius
In 861 the Byzantine Emperor Michael III sent the two brothers to convert the Khazars to Christianity. They continued their religious conversion of the Tatars along the Black Sea for two years. Afterwards the Emperor Michael sent them to Moravia as missionaries. They taught in the Slavic languages and translated the Scriptures into Slavonic. Cyril invented an alphabet called the Glagolitic alphabet. This became the basis for the Cyrillic alphabet. Old Church Slavonic was written in Cyrillic and Glagolitic.