The sixth century AD saw the migration of the Slav people from old Poland. The Slavs expanded westwards to the river Elbe and southwards to the Adriatic sea where they gradually occupied much of the Balkans (more detailed account of Russian history). By the tenth century, three Slavonic language groups had emerged: Western, Southern and Eastern. Eastern Slavonic gave rise to the modern languages known as Ukranian, Belorussian and Russian. The Slavonic languages retained many features in common especially in grammatical structure, therefore the separate groups were able to use one common written language.

This language was known as Old Slavonic or Old Church Slavonic (the language was used in its written form only). In the ninth century, two missionaries - Constantine (who on his deathbed took the monastic name Cyril) and Methodius - were required to write down the scriptures in Old Church Slavonic and to preach Christianity to the people of Moravia. Before they set out for Moravia, Constantine invented a Slavonic, now known as the Cyrillic alphabet. The Cyrillic alphabet is closely based on the Greek alphabet, with about a dozen additional letters invented to represent Slavic sounds not found in Greek