https://www.history.com/this-day-in-history/ussr-established?cmpid=email-hist-tdih-2020- [login to see] 0&om_rid=
In post-revolutionary Russia, the Union of Soviet Socialist Republics (USSR) is established, comprising a confederation of Russia, Belorussia, Ukraine, and the Transcaucasian Federation (divided in 1936 into the Georgian, Azerbaijan, and Armenian republics). Also known as the Soviet Union, the new communist state was the successor to the Russian Empire and the first country in the world to be based on Marxist socialism.