Communist governments were initially installed, mostly in places that had been controlled by the Axis countries and occupied due to the victories of the Soviet Union on the Eastern Front (World War II). The process included extensive political and media controls, along with a Soviet approach to restricting emigration. Events such as the split of Josip Broz Tito and Berlin Blockade prompted stricter control. While certain oppositional factions in the Bloc had revolts, such as the Hungarian Revolution of 1956 and the Warsaw Pact invasion of Czechoslovakia, Mikhail Gorbachev's perestroika experienced inefficiencies and stagnation throughout much of the Bloc preceding the Bloc's dissolution. Counterrevolutions in 1989 dissolved the Soviet Bloc.