In 862 A.D. Kievan Rus', the first united East Slavic state, was founded in 882. The state adopted Christianity from the Byzantine Empire in 988, beginning with the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium.
In 882 a Viking leader, Oleg, moves his headquarters down the Dnieper, seizing the town of Kiev. Here, in 911, he negotiates a commercial treaty with the Byzantine empire.