the 7th century onwards, the East Slavs constituted the bulk of the population in western Russia, and slowly but peacefully assimilated the native Finnic peoples. Kievan Rus' The establishment of the first East Slavic states in the 9th century coincided with the arrival of Varangians, the Vikings who ventured along the waterways extending from the eastern Baltic to the Black and Caspian Seas. According to the Primary Chronicle, a Varangian from the Rus' people, named Rurik, was elected ruler of Novgorod in 862. In 882, his successor Oleg ventured south and conquered Kiev, which had been previously paying tribute to the Khazars. Rurik's son Igor and Igor's son Sviatoslav subsequently subdued all local East Slavic tribes to Kievan rule, destroyed the Khazar Khaganate, and launched several military expeditions to Byzantium and Persia. In the 10th to 11th centuries, Kievan Rus' became one of the largest and most prosperous states in Europe. The reigns of Vladimir the Great (980–1015) and his son Yaroslav the Wise (1019–1054) constitute the Golden Age of Kiev, which saw the acceptance of Orthodox Christianity from Byzantium, and the creation of the first East Slavic written legal code, the Russkaya Pravda. The age of feudalism and decentralisation had come, marked by constant in-fighting between members of the Rurik dynasty that ruled Kievan Rus' collectively. Kiev's dominance waned, to the benefit of Vladimir-Suzdal in the north-east, the Novgorod Republic in the north, and Galicia-Volhynia in the south-west. By the 12th century, Kiev lost its pre-eminence and Kievan Rus' had fragmented into different principalities. Prince Andrey Bogolyubsky sacked Kiev in 1169 and made Vladimir his base, leading to political power being shifted to the north-east. Led by Prince Alexander Nevsky, Novgorodians repelled the invading Swedes in the Battle of the Neva in 1240, as well as the Germanic crusaders in the Battle on the Ice in 1242. Kievan Rus' finally fell to the Mongol invasion of 1237–1240, which resulted in the sacking of Kiev and other cities, as well as the death of a major part of the population. The invaders, later known as Tatars, formed the state of the Golden Horde, which ruled over Russia for the next two centuries. The Novgorod Republic escaped Mongol occupation after it surrendered and agreed to pay tribute, while Polotsk and part of Smolensk avoided invasion but came under the influence of Lithuania. Galicia-Volhynia would later be absorbed by Lithuania and Poland,