The Russian Civil War was a multi-party civil war in the former Russian Empire sparked by the overthrowing of the social-democratic Russian Provisional Government in the October Revolution, as many factions vied to determine Russia's political future. It resulted in the formation of the Russian Socialist Federative Soviet Republic and later the Soviet Union in most of its territory. Its finale marked the end of the Russian Revolution, which was one of the key events of the 20th century.

The Russian Empire, also known as Imperial Russia or simply Russia, was a vast realm that spanned most of northern Eurasia from its proclamation in November 1721 until its dissolution in March 1917. At its height in the late 19th century, it covered about 22,800,000 square kilometres (8,800,000 sq mi), roughly one-sixth of the world's landmass, making it the third-largest empire in history, surpassed only by the British and Mongol empires; it also held colonies in North America between 1799 and 1867. The empire's 1897 census, the only one it conducted, found a population of 125.6 million with considerable ethnic, linguistic, religious, and socioeconomic diversity.