The Bolshevik Party, under the leadership of Vladimir Lenin, managed to take control of Petrograd (now St Petersburg) by taking over government* and other strategic buildings in the Russian capital in an almost bloodless coup.

Lenin became dictator of the new country, called, initially, Bolshevik Russia. It was the world's first Marxist state.

Lenin's government made peace with Germany (who the Russians were fighting in WW1) and nationalized industry and distributed land.

In 1918 the new government was forced to fight the Czarist forces in a civil war. The Czarist forces were beaten in 1920. The country changed it's name to the Union of Soviet Socialist Republics (USSR) in 1922.

Lenin died in 1924. Joseph Stalin replaced him.

*Back story:

Following the abdication of Czar Nicholas II in this year's February Revolution (which was on 15th March 1917, it was called the February Revolution because Russia used the Julian calendar) the country was being run by a largely ineffective provisional government.