ELI5: Explain Like I'm 5

Brezhnev Doctrine

The Brezhnev Doctrine was a foreign policy of the Soviet Union. It said that if a country in the eastern half of Europe changed its government to something different than communism (the political system in the Soviet Union), the Soviet Union would step in and try to make that country become a Communist country again. This was meant to keep the eastern half of Europe from breaking away from the Soviet Union and becoming free.