or Warsaw Treaty Organization
Military alliance of the Soviet Union, Albania (until 1968), Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania, formed in 1955 in response to West Germany's entry into NATO .
Its terms included a unified military command and the stationing of Soviet troops in the other member states. Warsaw Pact troops were called into action to suppress uprisings in Poland (1956), Hungary (1956), and Czechoslovakia (1968). The alliance was dissolved in 1991 after the collapse of the Soviet bloc, and Soviet troops departed. Several Warsaw Pact members later joined NATO.