45th Anniversary Of 1968 Soviet-Led Invasion Of Czechoslovakia Soviet troops and most of their Warsaw Pact allies invaded Czechoslovakia on August 21, 1968, to halt political liberalization in the country called the Prague Spring. About 500,000 troops invaded and occupied Czechoslovakia in an operation code-named "Danube." Some 500 Czechoslovaks were wounded and 108 killed in the invasion, which successfully ended political and economic reforms under the leadership of Alexander Dubcek and gave the Communist Party greater authority. The Soviet-led invasion helped establish the Brezhnev Doctrine, which Moscow said allowed the U.S.S.R. to intervene in any country where a Communist government was under threat. The occupation of Czechoslovakia lasted until 1991.