The Russian Civil War (1917–1923) was a multi-party war that occurred within the former Russian Empire after the Russian provisional government collapsed and the Soviets under the domination of the Bolshevik party assumed power, first in Petrograd (St. Petersburg) and then in other places.
Following the abdication of Nicholas II of Russia and the turbulent Russian Revolution throughout 1917, the Russian Provisional Government was established. In October another revolution occurred in which the Red Guard, armed groups of workers and deserting soldiers directed by the Bolshevik Party, seized control of Saint Petersburg (then known as Petrograd) and began an immediate armed takeover of cities and villages throughout the former Russian Empire.
The Bolsheviks decided to immediately make peace with the German Empire and the Central Powers, as they had promised the Russian people prior to the Revolution.
In January 1918, after significant reverses in combat, War Commissar Leon Trotsky headed the reorganization of the Red Guard into a Workers' and Peasants' Red Army, in order to create a more professional fighting force. Political commissars were appointed to each unit of the army to maintain morale and ensure loyalty.
While resistance to the Red Guard began on the very next day after the Bolshevik uprising, the Brest-Litovsk treaty and the political ban became a catalyst for the formation of anti-Bolshevik groups both inside and outside Russia, pushing them into action against the new regime.
A loose confederation of anti-Bolshevik forces aligned against the Communist government, including land-owners, republicans, conservatives, middle-class citizens, reactionaries, pro-monarchists, liberals, army generals, non-Bolshevik socialists who still had grievances and democratic reformists, voluntarily united only in their opposition to Bolshevik rule. Their military forces, bolstered by foreign influence and led by General Yudenich, Admiral Kolchak and General Denikin, became known as the White movement (sometimes referred to as the "White Army"), and they controlled significant parts of the former Russian empire for most of the war.
The majority of the fighting ended in 1920 with the defeat of General Pyotr Wrangel (of the Whites) in the Crimea, but a notable resistance in certain areas continued until 1923 (e.g, Kronstadt Uprising, Tambov Rebellion, Basmachi Revolt, and the final resistance of the White movement in the Far East).