Czarist and revolutionary background
The February Revolution replaced the Tsar with the Russian Provisional Government, 1917 which was itself overthrown by the Bolshevik Revolution of 1917. The Russian army, exhausted by its participation in World War I, was in the final stages of disintegration and collapse. Even though Bolshevik influence in the ranks was strong, the officer corps was staffed with many who violently opposed communism. The Bolsheviks perceived the Tsarist army to be one of the foundations of the hated old regime, and decided to abolish it in favor of establishing a new military loyal to the Marxist cause. Thus the core of the Tsarist army became the core of the Russian Provisional Government army which became the core of the White Army, which in intermittent collaboration with interventionist forces from outside Russia (Japanese, British, French, American) battled the Red Army during the Russian Civil War.
On January 28, 1918 the Bolshevik leader Vladimir Lenin decreed the establishment of the Red Army, officially merging the 20,000 Red Guards, 60,000 Latvian red riflemen with 200,000 Baltic Fleet sailors and a handful of sympathetic Petrograd garrison soldiers. Leon Trotsky served as their first commissar for war.
The early Red Army was egalitarian and therefore poorly disciplined. The Bolsheviks considered military ranks and saluting to be bourgeois customs and abolished them; soldiers now elected their own leaders and voted on which orders to follow. This arrangement was abolished, however, under pressure of the Russian Civil War (1918–21), and ranks were reinstated.
During the civil war, the Bolsheviks fought counterrevolutionary groups that became known as the White armies as well as armies sponsored by Russia's former allies such as the Britain and France, which saw a need to overthrow the Bolshevik government. The Red Army enjoyed a series of initial victories over their opponents, and in a surge of optimism Lenin ordered the Soviet Western Army to advance West in the vacuum created by the German forces retreating from the Ober-Ost areas. This operation swept the newly formed Ukrainian People's Republic and Belarusian People's Republic and eventually lead to the Soviet invasion of Second Polish Republic, a newly independent state of the former Russian Empire. By invading Poland and initiating the Polish-Soviet War the Bolsheviks expressed their belief that they would eventually triumph over opposing capitalist forces both at home and abroad.
The overwhelming majority of professional officers in the Russian army were of nobility (dvoryanstvo); moreover, most of them had joined the White armies. Therefore, the Workers' and Peasants' Army initially faced a shortage of experienced military leaders. To remedy this, the Bolsheviks recruited 50,000 former Imperial Army officers to command the Red Army. At the same time, they attached political commissars to Red Army units to monitor the actions and loyalty of professional commanders, formally termed as "military specialists" (voyenspets, for voyenny spetsialist). By 1921 the Red Army had defeated four White armies and held off five armed foreign contingents that had intervened in the civil war, but began to face setbacks in Poland.
Polish forces managed to break a long streak of Bolshevik victories by launching a bold counteroffensive at the Battle of Warsaw in August 1920. At Warsaw the Red Army suffered a defeat so great and so unexpected that it turned the course of the entire war and eventually forced the Soviets to accept the unfavorable conditions offered by the Treaty of Riga, signed on March 18, 1921. It was the biggest defeat of the Red Army in history.
After the civil war, the Red Army became an increasingly professional military organization. With most of its five million soldiers demobilized, the Red Army was transformed into a small regular force, and territorial militias were created for wartime mobilization. Soviet military schools, established during the civil war, began to graduate large numbers of trained officers loyal to the Soviet power. In an effort to increase the prestige of the military profession, the party reestablished formal military ranks, downgraded political commissars, and eventually established the principle of one-man command.