The nation's history began with that of the East Slavs, who emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, the first East Slavic state, Kievan Rus', arose in the 9th century and adopted Orthodox Christianity from the Byzantine Empire in 988, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Kievan Rus' ultimately disintegrated into a number of smaller states; most of the Rus' lands ultimately were overrun by the Mongol invasion and became tributaries of the nomadic Golden Horde. The Grand Duchy of Moscow gradually reunified the surrounding Russian principalities, achieved independence from the Golden Horde, and came to dominate