The origin of the RCSN is, of course, the destruction of the old world. Since the Soviet Union kept careful diplomatic relations with both sides of the conflict, they were not a main target for either the United States or the People's Republic of China. Of course, their cities still were bombed when the day came, as were most capitals in the world in that madness, but a great number of their military bases were left untouched as largely irrelevent to the conflict between the US and China.
In a world in ruins, the Red Army could have very well dedicated themselves to pillage, or the law of the jungle, but a visionary came forth: General Arkadiy Radimov, creator of the doctrine of Reborn Communism. He saw the apocalypse as an opportunity to rise from the ashes, like a phoenix, and bring Communism to life in a way that wasn't possible in the formerly superpopulated world. He quickly united the Red Army under one flag, and they restored order in the land. Those were hard, tough years of war and conquest, but from the ashes of the Soviet Union, the Reborn Coalition of Soviet Nations finally rose.
Today, the RCSN is one of the most powerful states on the face of the Earth. They are a militarized society, and they live by a special interpretation of Communist precepts. It does not exactly mirror the Marxist-Leninist origins of Communism, and that difference has resulted in a new Bolshevik rebellion. The Bolsheviks of 2277-78 are a small, but vocal minority who wish to restore the old Soviet way of life, by force if necessary. The most noteworthy action by this Bolsehviks is the inflitration of the RCSN Presidential compound and the capture of General Orlov, which solidified the alliance between the RCSN and the TSC.