On the night of 20/21 August 1968 troops of the Warsaw Pact under Soviet command invaded Czechoslovakia in order to suppress the Prague Spring – liberalisation reforms of Alexander Dubček's government.
The Prague Spring began when Alexander Dubček was elected First Secretary of the Czechoslovakia Communist Party. His reforms aimed at granting additional rights to the citizens of Czechoslovakia by partial decentralization of the economy and democratization. The freedoms granted included also a loosening of restrictions on the media, speech and travel.
The reforms, especially the decentralization of administrative authority, were not received well by the Soviets, who, after failed negotiations, sent almost half a million Warsaw Pact troops and tanks to occupy the country. On the night of 20/21 August 1968 troops of the Warsaw Pact entered Czechoslovakia. Together with the Soviet army, there were Polish, Bulgarian and Hungarian troops.
Czechoslovakia was not ready to resist the invasion, which ended as a success in political and military terms. Despite social opposition and manifestations, the voice of the Prague Spring was silenced. Additionally, a contingent of Soviet troops remained in Czechoslovakia. The invasion resulted in about a hundred civilians killed and further 500 wounded among the Czechs and Slovaks. Alexander Dubček was arrested in the morning of 21 August and taken to Moscow along with several of his colleagues. Later they were returned to Prague, and Dubček retained his post as the party's first secretary until he was forced to resign in April 1969.
The invasion was followed by an unprecedented wave of emigration, largely of highly qualified people, according to the estimates 70.000 people left Czechoslovakia immediately after the invasion, and the total number of emigrants reached 300.000.