The Soviet Union - officially called the Union of Soviet Socialist Republics (USSR) - was a Marxist-Leninist federal state that existed in Eurasia between 1922 and 1991.
The USSR was born as a union of four Soviet socialist republics, formed after the October Revolution of 1917, and grew to 15 by 1956.
Over and above the errors that led to its disappearance, this country played an essential role in the defeat of fascism and in the advance of humanity towards new forms of social organization that were more cooperative and in solidarity.