On the night of 20–21 August 1968, Eastern Bloc armies from five Warsaw Pact countries (the Soviet Union, Poland, East Germany, Hungary and Bulgaria) invaded Czechoslovakia. The invasion comported with the Brezhnev Doctrine, a policy of compelling Eastern Bloc states to subordinate national interests to those of the Bloc as a whole and the exercise of a Soviet right to intervene if an Eastern Bloc country appeared to shift towards capitalism. The invasion was followed by a wave of emigration, including an estimated 70,000 Czechoslovaks initially fleeing, with the total eventually reaching 300,000.