The Socialist Revolution in Russia led to the formation of the Union of Soviet Socialist Republics (USSR) in 1917. This revolution was a result of the growing discontent among the Russian people towards the autocratic rule of the Tsarist regime.

Key events leading to the formation of the USSR:

1. February Revolution: In February 1917, a series of protests and strikes broke out in Petrograd (now St. Petersburg), the capital of Russia. These protests were triggered by food shortages, high taxes, and the loss of Russian soldiers in World War I. The Tsarist regime was unable to control the unrest, and the army joined the protests, forcing Tsar Nicholas II to abdicate.

2. Provisional Government: Following the Tsar's abdication, a Provisional Government was formed to govern Russia. However, it was weak and unable to resolve the country's problems.

3. Bolshevik Revolution: In October 1917, the Bolshevik party, led by Vladimir Lenin, seized power from the Provisional Government in a coup d'état. They established a new government based on Marxist principles, known as the Soviet government. The Bolsheviks renamed themselves the Communist Party of the Soviet Union.

4. Formation of the USSR: In December 1922, the Communist Party of the Soviet Union established the Union of Soviet Socialist Republics (USSR), a federal socialist state comprising of Russia and several other Soviet republics.

In conclusion, the USSR came into being after the Socialist Revolution in Russia in 1917, which led to the establishment of a new Soviet government and the formation of the USSR.