In 864 AD, the Byzantine monks Cyril and Methodius were sent North by the Byzantine government to convert the Balkans to Christianity. They were successful in the Kievan Rus. Their biggest contribution is that they developed an alphabet based on a modified Greek script, which we now call Cyrillic. Kievan Rus also traded with the Byzantines along the Dnieper River and the Black Sea. Under Vladimir I, Kievan Rus converted to Orthodox Christianity. He also married the Byzantine emperor's sister. During those times, Rus continued to imitate Byzantine culture, language and law.