The Bolsheviks (Большевики́, from большинство́ boľšinstvó, 'majority') were a far-left, revolutionary Marxist faction founded by Vladimir Lenin that split with the Mensheviks from the Marxist Russian Social Democratic Labour Party (RSDLP), a revolutionary socialist political party formed in 1898, at its Second Party Congress in 1903.
After forming their own party in 1912, the Bolsheviks took power during the October Revolution in the Russian Republic in November 1917, overthrowing the Provisional Government of Alexander Kerensky, and became the only ruling party in the subsequent Soviet Russia and later the Soviet Union. They considered themselves the leaders of the revolutionary proletariat of Russia. Their ideology and practices were often referred to as Bolshevism.
Lenin's political pamphlet What Is to Be Done?, written in 1901, helped to precipitate the Bolsheviks' split from the Mensheviks. In Germany, the book was published in 1902, but in Russia, strict censorship outlawed its publication and distribution. One of the main points of Lenin's writing was that a revolution can only be achieved by a strong, professional leadership with deep dedication to Marxist theoretical principles and an organization that spanned through the whole of Russia, abandoning what Lenin called "artisanal work" towards a more organized revolutionary work. After the proposed revolution had successfully overthrown the Russian autocracy, this strong leadership would relinquish power and allow a Socialist party to fully develop within the principles of democratic centralism. Lenin said that if professional revolutionaries did not maintain influence over the fight of the workers, then that fight would steer away from the party's objective and carry on under the influence of opposing beliefs or even away from revolution entirely.
The pamphlet also showed that Lenin's view of a socialist intelligentsia was in line with Marxist theory. For example, Lenin agreed with the Marxist ideal of social classes ceasing to be and for the eventual "withering away of the state".