Kievan Rus' (Russian: Киевская Русь, tr. Kievskaya Rus' ) was a medieval state in early Russia. Located in the present-day areas of Russia, Belarus and Ukraine, it existed from the 9th to the 13th centuries. It originated with Norse rulers that came down from Novgorod to establish a ruling dynasty in Kiev, and reached its peak under Yaroslav the Wise in the 11th century. Its influence declined in favor of more northerly cities by the 13th century, and it collapsed following the Mongol invasions in 1223. Kievan Rus' introduced Orthodox Christianity into Russia, created the first Russian code of laws and greatly increased literacy through religious education.
Around the 8th century AD, modern-day European Russia was inhabited by various different peoples, including Uralic, Finno-Ugric, Slavic and Turkic peoples. At that time, the Slavic peoples that came to dominate Russia later on lived mostly in the areas of modern-day Ukraine, Belarus and Poland. The Kievan Rus culture began to arise as these peoples spread to the east, experiencing cultural exchange with their Uralic neighbors. Scandinavians had been trading along the Volga River during this time period, as a way to access Byzantine riches. In the mid 800s, Rurik, a figure of disputed origins, came from Scandinavia and ruled over Novgorod. His descendants established the Rurikid Dynasty in Kiev. Through a system of Grand Princes nominally ruling over smaller princes, Russia was divided into many small states, with Kiev as the main political center.
In 988, Grand Prince Vladimir I of Kiev led a mass baptism of people in the river Dniepr, which symbolized the conversion of Rus to Christianity. Around that time, Slavic people began displacing Uralic peoples throughout modern-day Russia. By the 12th century, there was still little political unity in the Russian states. Many of them were at the mercy of Muslim lords from the south, who would sporadically raid Slavic villages and capture people for slavery. Farther north, Teutonic knights would repeatedly invade and try to convert Russian states to Roman Catholicism. Sometimes called the Northern Crusade, these attacks were largely repulsed, made famous by the Battle of the Ice on Lake Peipus. There, heavily armed Teutonic horsemen battled a Novgorodian militia led by Alexander Nevsky, gradually being driven back onto the frozen lake until the armor-clad cavalry began falling through the ice. This constant warfare would give rise to a military culture in Russia.
By the 10th century, the Norse and Slavic groups had merged, and Orthodox Christianity became widespread. Sviatoslav I defeated the Khazars in the southern steppe, and Constantinople was raided several times. Russkaya Pravda was introduced as the earliest code of laws in Russia, while princes took the Byzantine example of a close church and state. This synthesis of Slavic, Norse and Greek elements would form the modern Russian culture. In the 12th century, particularly under Yaroslav the Wise, Russian culture flourished and literacy was much higher than in Western Europe at the time.
Continuing attacks and invasions by nomadic steppe peoples in the south led to a migration of Slavs to the safer, more northern region of Zalesye. The influence of Kiev waned, while the northern regions of Novgorod and Vladimir benefited from this. In 1223, Mongol invaders defeated a disunited army of southern Russian princes at the Kalka river. This began the Mongol invasion of Russia, in which Moscow, Kiev, Vladimir and other major cities were destroyed. Southern and central Russia were occupied by the Mongols, who forced the Russian princes to pay tribute. Novgorod, part of the Hanseatic League, was largely spared of the Mongol terror due to its northern location. Kiev, however, was completely destroyed. The Mongol invasions marked a major turning point in Russian history, shifting the political strength from south to north and isolating Russia from the rest of Europe.