Socialism rose in response to the Industrial Revolution across Europe in the late 19th century. This also led to the growth of socialist political parties in the early 20th century. Socialist parties sought to organize socialist ideas in an effort to make large scale reforms on government.
Russia had a series of issues needing large scale reforms. The slow industrial process after the abolition of serfdom, left many unemployed or underemployed. The government had been involved in costly wars, such as the Crimean War, and now WWI.
The Bolshevik Party formed in Russia under the leadership of Vladimir Lenin. Lenin had been exiled for Marxist activities. Funded by the Germans, he returned to begin a revolution in Russia. The Bolshevik Party overpowered the Menshevik Party (more moderate) and pressured Tsar Nicholas II to reform.
In 1915, Tsar Nicholas II left Petrograd (renamed St. Petersburg) to command the Russian forces against Germany after key losses. In his absence, the Russian people began protesting in the streets over government corruption and food shortages. (Nicholas was known for disbanding the Duma when they disagreed with his policies. His wife was firing elected officials in his absence.)
The February/March Revolution, then, sparked. In 1917, the Russian Duma, or legislative assembly, formed a Provisional Government. Tsar Nicholas II chose to abdicate the throne, seeing as how he would have no legitimate means of continuing the Romanov line. His son had hemophilia and could bleed out from even a slight injury,
Tsar Nicholas II and his family were removed from Petrograd for their “safety” and taken by Bolshevik forces out of the city where they were all murdered alongside their closest servants and staff. This is the end of the Romanov line in Russia that lasted over 300 years.
After Tsar Nicholas II abdicated, the Bolshevik Party took over the Provisional Government with Vladimir Lenin as their leader. His New Economic Policy implemented elements of capitalism into an otherwise communist government. Many did not agree with these policies or sought after liberal reforms not recognized by the Bolsheviks.
Civil War broke out in late 1917 between the Red Army of the Bolsheviks and the White Army of the monarchists that sought liberal reforms. After years of fighting and over 7 million deaths, mostly civilians, the war ended in 1923 with the Red Army controlling Russia and many states on the Russian border. Vladimir Lenin was now in control of a newly formed union of communist states called the Soviet Union.