Political repression in the Soviet Union

Throughout the history of the Soviet Union, tens of millions of people suffered political repression, which was an instrument of the state since the October Revolution. It culminated during the Stalin era, then declined, but it continued to exist during the "Khrushchev Thaw", followed by increased persecution of Soviet dissidents during the Brezhnev era, and it did not cease to exist until late in Mikhail Gorbachev's rule when it was ended in keeping with his policies of glasnost and perestroika.