The February Revolution (March 1917) was a revolution focused around Petrograd (now Saint Petersburg), the capital of Russia at that time. In the chaos, members of the Imperial parliament (the Duma) assumed control of the country, forming the Russian Provisional Government which was heavily dominated by the interests of large capitalists and the noble aristocracy. The army leadership felt they did not have the means to suppress the revolution, resulting in Nicholas's abdication. The soviets, which were dominated by soldiers and the urban industrial working class, initially permitted the Provisional Government to rule, but insisted on a prerogative to influence the government and control various militias. The February Revolution took place in the context of heavy military setbacks during the First World War (1914–18), which left much of the Russian Army in a state of mutiny.
A period of dual power ensued, during which the Provisional Government held state power while the national network of soviets, led by socialists, had the allegiance of the lower classes and, increasingly, the left-leaning urban middle class. During this chaotic period there were frequent mutinies, protests and many strikes. Many socialist political organizations were engaged in daily struggle and vied for influence within the Duma and the soviets, central among which were the Bolsheviks ("Ones of the Majority") led by Vladimir Lenin who campaigned for an immediate end to the war, land to the peasants, and bread to the workers. When the Provisional Government chose to continue fighting the war with Germany, the Bolsheviks and other socialist factions were able to exploit virtually universal disdain towards the war effort as justification to advance the revolution further. The Bolsheviks turned workers' militias under their control into the Red Guards (later the Red Army) over which they exerted substantial control.
In the October Revolution (November in the Gregorian calendar), the Bolsheviks led an armed insurrection by workers and soldiers in Petrograd that successfully overthrew the Provisional Government, transferring all its authority to the soviets with the capital being relocated to Moscow shortly thereafter. The Bolsheviks had secured a strong base of support within the soviets and, as the now supreme governing party, established a federal government dedicated to reorganizing the former empire into the world's first socialist republic, practicing soviet democracy on a national and international scale. The promise to end Russia’s participation in the First World War was honored promptly with the Bolshevik leaders signing the Treaty of Brest-Litovsk with Germany in March 1918. To further secure the new state, the Cheka was established which functioned as a revolutionary security service that sought to weed out and punish those considered to be "enemies of the people" in campaigns consciously modeled on similar events during the French Revolution.
Soon after, civil war erupted among the "Reds" (Bolsheviks), the "Whites" (counter-revolutionaries), the independence movements and the non-Bolshevik socialists. It continued for several years, during which the Bolsheviks defeated both the Whites and all rival socialists and thereafter reconstituted themselves as the Communist Party. In this way, the Revolution paved the way for the creation of the Union of Soviet Socialist Republics (USSR) in 1922. While many notable historical events occurred in Moscow and Petrograd, there was also a visible movement in cities throughout the state, among national minorities throughout the empire and in the rural areas, where peasants took over and redistributed land.
The Russian Revolution of 1905 was said to be a major factor contributing to the cause of the Revolutions of 1917. The events of Bloody Sunday triggered nationwide protests and soldier mutinies. A council of workers called the St. Petersburg Soviet was created in this chaos. While the 1905 Revolution was ultimately crushed, and the leaders of the St. Petersburg Soviet were arrested, this laid the groundwork for the later Petrograd Soviet and other revolutionary movements during the leadup to 1917. The 1905 Revolution also led to the creation of a Duma (parliament), that would later form the Provisional Government following February 1917.