From mid-1917 onwards, the Russian Army, the successor-organisation of the old Imperial Russian Army, started to disintegrate; the Bolsheviks used the volunteer-based Red Guards as their main military force, augmented by an armed military component of the Cheka (the Bolshevik state security apparatus). In January 1918, after significant Bolshevik reverses in combat, the future People's Commissar for Military and Naval Affairs, Leon Trotsky headed the reorganization of the Red Guards into a Workers' and Peasants' Red Army in order to create a more effective fighting force. The Bolsheviks appointed political commissars to each unit of the Red Army to maintain morale and to ensure loyalty.

In June 1918, when it had become apparent that a revolutionary army composed solely of workers would not suffice, Trotsky instituted mandatory conscription of the rural peasantry into the Red Army. The Bolsheviks overcame opposition of rural Russians to Red Army conscription units by taking hostages and shooting them when necessary in order to force compliance. The forced conscription drive had mixed results, successfully creating a larger army than the Whites, but with members indifferent towards Marxist–Leninist ideology.

The Red Army also utilized former Tsarist officers as "military specialists" (voenspetsy); sometimes their families were taken hostage in order to ensure their loyalty. At the start of the civil war, former Tsarist officers formed three-quarters of the Red Army officer-corps. By its end, 83% of all Red Army divisional and corps commanders were ex-Tsarist soldiers.