Kievan Rus

Kievan Rus was a loose federation of East Slavic and Finnic peoples in Europe that existed from the late ninth century to the mid-thirteenth century, traditionally founded when the Varangian prince Oleg of Novgorod took control of Kiev around 882 and made it his capital, building on an earlier Rurikid principality established at Novgorod. The state reached its height in the late tenth and eleventh centuries under rulers including Vladimir the Great, who adopted Byzantine Christianity as the state religion around 988, and Yaroslav the Wise, under whom Kiev became a major center of trade, culture and law codified in the Russkaya Pravda. Kievan Rus was never a fully centralized state but rather a confederation of principalities loosely bound by a ruling Rurikid dynasty, shared Orthodox Christian faith, and control of the trade route linking the Varangians to the Byzantine Empire, and it fragmented increasingly into rival principalities from the twelfth century onward. The Mongol invasion led by Batu Khan devastated the Rus principalities between 1237 and 1240, including the sack of Kiev itself in 1240, bringing the political unity of Kievan Rus to an end and subjecting its successor principalities to the overlordship of the Golden Horde.