One day after the October Revolution, on November 8, 1917, the Bolsheviks headed by N. Anisimov seized Grozny. As the Russian Civil War escalated, the Proletariat formed the 12th Red Army, and the garrison held out against numerous attacks by Terek Cossacks from August 11 to November 12, 1918. However, with the arrival of Denikin's armies, the Bolsheviks were forced to withdraw and Grozny was captured on February 4, 1919, by the White Army. Underground operations were carried out, but only the arrival of the Caucasus front of the Red Army in 1920 allowed the city to permanently end up with the Russian SFSR on March 17. Simultaneously it became part of the Soviet Mountain Republic, which was formed on January 20, 1921, and was the capital of the Chechen National Okrug inside it.