An armed uprising against Soviet power by the units of the Czechoslovak Legion, a volunteer military unit formed mainly from former military personnel (prisoners of war and defectors) of the Austro-Hungarian army to act on the side of the Entente. At the end of 1917, the Legion in Russia was formally subordinate to the French command and was to be sent to the Western Front. To this end, the Legion units with weapons were sent to Vladivostok to be transferred from there by sea to France. By May 1918, echelons of the Czechoslovakians had stretched along the railroad from Penza to Vladivostok.

On May 14, the Chelyabinsk incident occurred, a conflict between the Hungarian prisoners and the soldiers of the Legion. 10 legionnaires were arrested by the Soviet authorities over the lynching of a Hungarian who had wounded heavily one of the Czechs. On May 17, the Czechoslovakians freed those arrested by force, disarmed the local Red Guard detachment, and seized weapons. In response, the Bolsheviks demanded that the Legion completely surrender their weapons. On May 20, the congress of Czechoslovak military delegates in Chelyabinsk decided not to surrender weapons and move to Vladivostok, elected the Provisional Executive Committee that consisted of Stanislav Chechek, Radola Gajda, and Sergey Voitsekhovsky. On May 25, 1918, the People’s Commissar for Military Affairs, Leon Trotsky, sent a telegram to the local Soviets in which he demanded to conduct complete disarmament of the Legion personnel and disband it. On May 25-27, n a significant part of the country, armed clashes broke out between the Legion units and the Bolsheviks.

By May 27, Czechoslovak units under the command of Radola Gajda captured Mariinsk. On May 26, Sergey Voitsekhovsky’s unit captured Chelyabinsk. Other units occupied the cities of Petropavlovsk and Kurgan along the Trans-Siberian Railway and opened their way to Omsk. On May 29, Stanislav Chechek’s unit, after a day-long bloody battle, captured Penza. At the end of May the Czechoslovakians occupied Tomsk. On June 4–5, they defeated the Soviet units near Samara and gained an opportunity to cross the Volga. On June 29, the Legion units organized a coup in Vladivostok.

The Legion’s revolt covered the vast area of the Volga region, the Urals, Siberia, and the Far East, creating a favorable situation for the revolt of the anti-Bolshevik groups, liquidation of Soviet authorities, and the formation of several anti-Bolshevik governments. Thus, in Samara, captured by the Czechoslovakians, on June 8, a Committee of Members of the Constituent Assembly (Komuch) was organized, and on June 30, in Omsk, the Provisional Siberian Government was established. So, the Legion’s revolt gave a start to large-scale hostilities in the framework of the Civil War in Russia. In July, to fight the Legion and other anti-Bolshevik forces, the leadership of Soviet Russia formed the Eastern Front under the command of Joakim Vatsetis (from September 1918 – by Sergei Kamenev). Further, the Legion’s units participated in the military actions against the Reds until the early 1920.