The Soviet Union was the name given to the the united countries that it was made up of Soviet Russia amd others. They are led the Communist Party while their primary intelligence arm is the KGB and were the main enemies alongside the Blisk in Destroy All Humans! 2.
In-game, under the leadership of Milenkov, the Kremlin of the Soviet Union started a revolution to defeat Crypto and Orthopox. In 1969, the Soviet Union launched a missile into space and destroyed the Furon Mothership, which killed both Orthopox and Gastro: the Mothership's janitor and cook. Pox and Gastro managed to escape to Earth with their conscious' inside HoloPox Units. KGB Agents then attempted to assassinate Crypto in Bay City, but Crypto managed to escape and recovered both Pox and Gastro. Afterwards, Project Solaris was approved and initiated: it successfully sent Cosmonauts and the Blisk to the Moon and created a moon base. After the discovery of the Blisk, Crypto destroyed the main factions of the Soviet Union and thereby crippled its hold over Tunguska. After the death of Milenkov and the Blisk, control of Russia was passed down to Leonid Brezhnev.
In real life see