Russian Primary Chronicle

Not all who considered themselves successors to Rome occupied former Roman borders. The relative wealth and order of the Frankish and Byzantine states proved attractive to the peoples north of the original Roman borders. The Franks and Byzantines were also interested in expanding their influence there. Because religion was not distinguished from politics at that time (or most time), Christianity spread to eastern Europe along with either Frank or Byzantine influence. By 1000 CE all of eastern Europe to the Ural Mountains was officially Christian, and powerful new states such as Hungary and Poland had formed. But western and eastern forms of Christianity had diverged to such an extent by then that eastern European rulers could treat them as different religions. Also, these rulers knew that their choice among the two Christianities was a choice to tie themselves more closely to either the Byzantines or the Franks. Poland and Hungary became western Christian states, aligning themselves with the Frankish world. The Rus, on the other hand, chose eastern Christianity and a closer relationship to Byzantium. The Rus were originally Scandinavian raiders who dominated the river systems of what is now western Russia and Ukraine. By the late tenth century they had adopted the Slavic language and culture of their subjects. This document from an early Russian chronicle describes how the Russian leader Vladimir chose to abandon his traditional gods and adopt Christianity. Notice how Vladimir is presented with a choice among Islam (Bulgarian), western Christianity (German), and eastern Christianity (Greek).