The History of Russia begins with that of the Eastern Slavs and the Finno-Ugric peoples.
The traditional beginning of Russian history is 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. Kievan Rus' ultimately disintegrated as a state because of the Mongol invasion of Rus' in 1237–1240 and the death of about half the population of Rus'.
After the 13th century, Moscow became a cultural center. By the 18th century, the Tsardom of Russia had become the huge Russian Empire, stretching from the Polish border eastward to the Pacific Ocean. Expansion in the western direction sharpened Russia's awareness of its separation from much of the rest of Europe and shattered the isolation in which the initial stages of expansion had occurred. Successive regimes of the 19th century responded to such pressures with a combination of halfhearted reform and repression. Peasant revolts were common, and all were fiercely suppressed. Russian serfdom was abolished in 1861, but the peasant fared poorly and often turned to revolutionary pressures. In following decades reforms efforts such as the Stolypin reforms, the constitution of 1906, and State Duma attempted to open and liberalize the economy and political system, but the tsars refused to relinquish autocratic rule or share their power.
The Russian Revolution in 1917 was triggered by a combination of economic breakdown, war-weariness, and discontent with the autocratic system of government, and it first brought a coalition of liberals and moderate socialists to power, but their failed policies led to seizure of power by the Communist Bolsheviks on 25 October. Between 1922 and 1991, the history of Russia is essentially the history of the Soviet Union, effectively an ideologically based state which was roughly conterminous with the Russian Empire before the Treaty of Brest-Litovsk. The approach to the building of socialism, however, varied over different periods in Soviet history, from the mixed economy and diverse society and culture of the 1920s to the command economy and repressions of the Joseph Stalin era to the "era of stagnation" in the 1980s. From its first years, government in the Soviet Union was based on the one-party rule of the Communists, as the Bolsheviks called themselves, beginning in March 1918.