From the mid-1940s through the mid-1980s, the threat of a Soviet invasion prevented the other Warsaw Pact countries from deviating from Moscow's prescribed domestic and foreign policies. The Soviet invasion of Hungary in 1956 demonstrated that Moscow would act if it believed that changes in that country threatened the security of the Warsaw Pact or the leading role of the communist party in Hungary. After economic reforms began in the 1960s, Hungary's government and party leaders were careful to take Soviet sensitivities into account. However, in the late 1980s, Moscow showed that it was sympathetic rather than hostile to reforms within Hungary, thus lessening the chances of a Soviet invasion.
Data as of September 1989