“[A] version of the Greek alphabet was devised by two bishops from Constantinople, Cyril and Methodius, for the Slavs to whom they brought Christianity in the ninth century. Faced with Slavic sounds which did not exist in Greek, they stretched the Greek alphabet as far as it would go, then drafted one or two Hebrew characters and invented others. The result was the Cyrillic alphabet used today by those nations which followed the Eatern Church—Russians, Ukranians, Serbs, and Bulgars.”

—Mario Pei, The Story of Language, 1965.