The revolt was led by the Left Socialist-Revolutionaries in Moscow.

Previously, the Socialist Revolutionary Party had supported the continuation of the war by the Provisional Government after the February Revolution of 1917.
The Bolshevik Party came to power in November 1917 through the simultaneous election in the soviets and an organized uprising supported by military mutiny.
Several of the main reasons the population supported the Bolsheviks were to end the war and have a social revolution, exemplified by the slogan "Peace, Land, Bread".
The Bolsheviks invited left SRs and Martov's Menshevik Internationalists to join the government.
Left SRs split from the main SR party and joined the Bolshevik coalition government, supporting the Bolsheviks immediate enactment of the Socialist Revolutionary Party's land redistribution program.
The Left SRs were given four Commissar positions and held high posts within the Cheka.
The Left SRs still diverged with the Bolsheviks on the issue of the war and were dismayed that the Treaty of Brest-Litovsk gave up large amounts of territory in Eastern Europe to the imperialist Central Powers.
With the treaty, the Left SRs considered that the opportunity to spread the revolution throughout Europe had been lost.
They left the Council of People's Commissars in protest in March 1918 and at the  4th Congress of Soviets they voted against the treaty.
Although they continued to work in the Cheka, which played a decisive role in rebellion.
Left Social Revolutionaries remained on the boards of the People's Commissars, the military department, various committees, commissions, and councils.

In Finland, where the soviet government had pledged by the treaty not to intervene, the landing of German troops significantly helped the "white" (counter-revolutionary) forces to crush the Finnish Revolution.
In Ukraine, a puppet government, the Hetmanate, had been established with German backing.
The forces of the Central Powers advanced through Ukraine towards Rostov-on-Don while Ottoman units made it into the Caucasus.
In March, Allied troops landed in Murmansk and reached the Russian Far East the next month.
In late May, clashes between the Russians and the Czechoslovak Legion began, and in June rival anti-Bolshevik governments were formed in Samara (the Komuch) and Omsk (the Provisional Siberian Government).
The Left SRs strongly objected to the invasion and opposed Trotsky's insistence that nobody was allowed to attack German troops in Ukraine.
Sergey Mstislavsky coined the slogan “It's not a war, it's an uprising!”,
calling on the “masses” to “rebel” against the German-Austrian occupation forces, accusing the Bolsheviks of creating a “state that obstructs the working class", moving away from the position of revolutionary socialism onto the path of opportunistic service to the state."

A new surge of tension was associated with an increase in the activity of the Bolsheviks in rural villages, when the Bolshevik-controlled government announced, by decree, the enforcement of a state bread monopoly and the organization of "food detachments" for the compulsory collection of bread.
On June 14, 1918, representatives of the Socialist-Revolutionary parties (both Left and Right) and the Mensheviks were expelled from the All-Russian Central Executive Committee by a Bolshevik decree.
By this same decree, all Soviets of workers, soldiers, peasants, and Cossack deputies were also invited to remove representatives of these parties from their midst.
Vladimir Karelin, a member of the Central Committee of the Left SRs, called this decree illegal, since only the All-Russian Congress of Soviets could change the composition of the All-Russian Central Executive Committee.
In early July, the Third Congress of the Left Socialist Revolutionary Party was held, in its resolution to the present moment sharply condemned the policy of the Bolsheviks:
Increased centralization, crowning the system of bureaucratic bodies with a dictatorship, the use of requisition units operating outside the control and leadership of local Soviets, the cul
The revolt was led by the Left Socialist-Revolutionaries in Moscow. 
Previously, the Socialist Revolutionary Party had supported the continuation of the war by the Provisional Government after the February Revolution of 1917. The Bolshevik Party came to power in November 1917 through the simultaneous election in the soviets and an organized uprising supported by military mutiny. Several of the main reasons the population supported the Bolsheviks were to end the war and have a social revolution, exemplified by the slogan "Peace, Land, Bread". The Bolsheviks invited left SRs and Martov's Menshevik Internationalists to join the government. Left SRs split from the main SR party and joined the Bolshevik coalition government, supporting the Bolsheviks immediate enactment of the Socialist Revolutionary Party's land redistribution program. The Left SRs were given four Commissar positions and held high posts within the Cheka. The Left SRs still diverged with the Bolsheviks on the issue of the war and were dismayed that the Treaty of Brest-Litovsk gave up large amounts of territory in Eastern Europe to the imperialist Central Powers. With the treaty, the Left SRs considered that the opportunity to spread the revolution throughout Europe had been lost. They left the Council of People's Commissars in protest in March 1918 and at the  4th Congress of Soviets they voted against the treaty. Although they continued to work in the Cheka, which played a decisive role in rebellion. Left Social Revolutionaries remained on the boards of the People's Commissars, the military department, various committees, commissions, and councils. 
In Finland, where the soviet government had pledged by the treaty not to intervene, the landing of German troops significantly helped the "white" (counter-revolutionary) forces to crush the Finnish Revolution. In Ukraine, a puppet government, the Hetmanate, had been established with German backing. The forces of the Central Powers advanced through Ukraine towards Rostov-on-Don while Ottoman units made it into the Caucasus. In March, Allied troops landed in Murmansk and reached the Russian Far East the next month. In late May, clashes between the Russians and the Czechoslovak Legion began, and in June rival anti-Bolshevik governments were formed in Samara (the Komuch) and Omsk (the Provisional Siberian Government). The Left SRs strongly objected to the invasion and opposed Trotsky's insistence that nobody was allowed to attack German troops in Ukraine. Sergey Mstislavsky coined the slogan “It's not a war, it's an uprising!”, calling on the “masses” to “rebel” against the German-Austrian occupation forces, accusing the Bolsheviks of creating a “state that obstructs the working class", moving away from the position of revolutionary socialism onto the path of opportunistic service to the state."
A new surge of tension was associated with an increase in the activity of the Bolsheviks in rural villages, when the Bolshevik-controlled government announced, by decree, the enforcement of a state bread monopoly and the organization of "food detachments" for the compulsory collection of bread. On June 14, 1918, representatives of the Socialist-Revolutionary parties (both Left and Right) and the Mensheviks were expelled from the All-Russian Central Executive Committee by a Bolshevik decree. By this same decree, all Soviets of workers, soldiers, peasants, and Cossack deputies were also invited to remove representatives of these parties from their midst. Vladimir Karelin, a member of the Central Committee of the Left SRs, called this decree illegal, since only the All-Russian Congress of Soviets could change the composition of the All-Russian Central Executive Committee. In early July, the Third Congress of the Left Socialist Revolutionary Party was held, in its resolution to the present moment sharply condemned the policy of the Bolsheviks:
Increased centralization, crowning the system of bureaucratic bodies with a dictatorship, the use of requisition units operating outside the control and leadership of local Soviets, the cul
Left SR uprising