Why did Russia quit fighting in WW1?

Answer 1

During World War I, Imperial Russia quit fighting in any organized and efficient manner in the fall of 1917 as a result of internal disorder. Stricken by a powerful (and eventually successful) revolution, Russia backed out of the fighting and then, in early 1918, formally made a separate peace with the Central Powers.

Answer 2

Russia stopped fighting in World War 1 because Vladimir Lenin and the Bolsheviks took over the government in the October Revolution in 1917 and then he entered into the Treaty of Brest-Litovsk with Germany to end Russia's role in the war.

One reason this happened was partly because the Russian Army was no longer a viable military force. It was poorly supplied, trained and led. It was no match for the modern German army and it suffered great losses. This led to widespread unrest in the ranks of the soldiers. Soldiers deserted by the thousands. Soldiers shot their own officers. Soldiers formed committees within their own units to decide what they would do on the battlefield rather than just take orders. The common soldier welcomed the Bolshevik revolution since it put Vladimir Lenin in position to end the war.