The Bolsheviks came to power in Russia through a nearly bloodless coup called the October Revolution. This coup occurred in early November 1917, eight months after the February Revolution that had deposed the Russian czar on March 15th and established a republic. Though the Bolsheviks were not the sole party participating in the October Revolution, they led the way and controlled most of the organs of power.
The October Revolution is, in fact, sometimes called the Bolshevik Revolution. Though the Bolsheviks had been active in left-wing politics in Russia for several years leading up to 1917, support for their dictatorial positions remained fairly tepid, with many more citizens preferring the more moderate policies of the Mensheviks and other revolutionaries. However, the horrors of World War I, the refusal of the government of the Russian Republic to end and an opposition characterized by internecine bickering gave the Bolsheviks the opportunity to control the revolutionary movement. They appealed to the masses with promises of, as Bolshevik leader Vladimir Lenin put it, "peace, land and bread." After deposing the republican government and winning a bloody civil war, the Bolsheviks remained in control of the U.S.S.R. until its fall in 1991. The discrepancy in the names of the February and October Revolutions and the dates during which they occurred is the result of the Russian use of the Julian calendar.