On the night of August 20–21, 1968, Warsaw Pact troops initially numbering about 300,000 (later reinforced to 500,000) occupied Czechoslovakia and violently ended the reforms implemented by Czechoslovak communists known as the “Prague Spring.” In bloody clashes between the invading forces and the civilian population, 72 Czechoslovaks were killed, 267 seriously injured, and 222 slightly injured by early September 1968. To justify the invasion, Soviet party leader Leonid Brezhnev proclaimed the so-called Brezhnev Doctrine on November 12, 1968: he claimed that the socialist states had only “limited sovereignty” and therefore there was not only the right but also the duty to intervene if socialism was threatened in one of these states. The picture shows a Soviet battle tank in the streets of Prague on August 21, 1968.