There were three reasons why Civil War broke out in Russia in 1918.
The first reason was that there was bound to be a challenge to the Bolsheviks, who had seized power by a surprise coup d’état. After 1918, their political opponents tried to reverse it. The Bolsheviks had many enemies. One group who wanted to destroy the Bolsheviks were the Social Revolutionaries. At first, they had supported the November Revolution. elections had been held in November 1917 for a new government – the Assembly – in which the Bolsheviks had won 175 seats and the Social Revolutionaries 370 seats. However, when it met in 1918, Lenin used the Red Guards to close the Assembly, and killed anybody who objected. The Social Revolutionaries fought back by attacking the Bolshevik government. The Bolsheviks were also opposed by the Mensheviks (who had controlled the Provisional Government, and who they had toppled from control of the Soviets in September), and by the Tsarists (who wanted to rescue Nicholas II and put him back on the throne). Lenin made peace with Germany (the Treaty of Brest-Litovsk, in which Russia had lost much of Russia’s best agricultural and industrial land to Germany, including Ukraine, Estonia, Latvia and Lithuania) and the former army officers were angry about this. Also, the Bolshevik government had taken land from the Tsar and the nobles and given it to the peasants, and the civil war was supported by those landlords who had lost their land. All these enemies of the Bolsheviks co-operated to try to bring down the Bolshevik government.
A second cause of the Civil War was the Czech Legion. These were some Czech prisoners of war being taken across Russia who in 1918 mutinied, took control of the Trans-Siberian Railway, and attacked towards Moscow.
these groups within Russia were helped by the Great Powers, angry that Russia
had dropped out of the First World War.
They were afraid because the Bolsheviks believed in World Revolution –
the Bolsheviks set up the Comintern, led by Zinoviev, which said it would cause
communist revolutions all over the world.
Consequently, the Allies sent armies to destroy the Bolsheviks
– British, American and French armies attacked from Archangel, Ukraine,