Informal name for the Warsaw Treaty Organization, a mutual defense organization founded in 1955, which included the Soviet Union, Albania (which withdrew in 1968), Bulgaria, Czechoslovakia, the German Democratic Republic (GDR, or East Germany), Hungary, Poland, and Romania. The Warsaw Pact enabled the Soviet Union to station troops in the countries to its west to oppose the forces of the North Atlantic Treaty Organization (NATO-- q.v.). The pact was the basis of the invasion of Hungary (1956) and of Czechoslovakia (1968); it was disbanded in July 1991.

A "treaty of friendship, co-operation, and mutual assistance" including the Soviet Union and its satellite states in Central Europe. Signed in 1955, it included eight countries.

the military organization of Eastern Europe signed in Warsaw, Poland in 1955, by Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Romania and the Soviet Union. It was a communist counterpart to NATO. Warsaw Pact members were bound to assist each other in the event of an attack on any one of them. Albania withdrew in 1961. The Warsaw Pact collaborated in the invasion of Czechoslovakia in 1968-the only time it took military action. The Pact was ended as a military alliance in 1991, when the demise of communism and the end of the Cold War made it superflous.