The Warsaw Pact was a treaty alliance of eight communist countries under the leadership of the Soviet Union which was formed several years after the end of World War II. Its true name was the Treaty of Friendship, Cooperation, and Mutual Assistance, and was ostensibly formed to protect its members from another attack from Germany as had occurred during the war. It was formed nine years after the war when the former West Germany (Federal Republic of Germany) joined the North Atlantic Treaty Organization (NATO.)Among its members were Albania, Poland, Bulgaria, Hungary, Poland, Romania and East Germany. Many historians believe that it was formed not so much as a defense against a future German invasion as a counter to the NATO alliance composed of Western ("free") Nations. Forces operating under the Pact's auspices were responsible for the invasion of Hungary in 1956 when that country attempted to withdraw from the alliance, and the invasion of Czechoslovakia in 1968. The Pact formally ended in 1991 with the collapse of communist governments in the member nations.
The Warsaw Pact is the name commonly given to the treaty between Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Romania, and the Soviet Union, which was signed in Poland in 1955 and was officially called 'The Treaty of Friendship, Co-operation and Mutual Assistance'. Although this rather cute title sounds more like the agreement which you and your friend have about sending cards to each other on Valentine's Day, it was actually a military treaty, which bound its signatories to come to the aid of the others, should any one of them be the victim of foreign aggression.
The Warsaw Pact was formed by Eastern-bloc nations (the Soviet Union and other Communist countries in Eastern Europe) in response to the North Atlantic Treaty Organization (NATO). NATO is a military alliance formed on April 4, 1949, when twelve Western countries signed the North Atlantic Treaty. Seeing the military and political significance of the Western nations forming a strong alliance, the Soviet Union and its allies met in Warsaw, Poland, in May 1955 to devise an answer to NATO. The nations signed a treaty and formed the Warsaw Pact, agreeing that they, too, would mutually defend one another. The eight member nations were Albania (withdrew in 1968), Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Rumania, and the Soviet Union. The Warsaw Pact was headquartered in Moscow, the capital of the Soviet Union and, in addition to discouraging attacks from NATO countries, the organization sought to quell any democratic uprisings in Warsaw Pact nations. Democracy (government based on individual freedom and on rule according to the will of the majority) was a threat to Communist governments, which were based on totalitarian (absolute) control of all aspects of life and denied the concept of individual freedom.
In 1990 the Pact, and the Soviet Union's control of it, weakened when democracy movements in member nations could not be stopped. As the former Eastern-bloc countries underwent relatively peaceful changes in government, Warsaw Pact members began announcing their intentions to withdraw from the organization. East Germany withdrew when it was reunified with West Germany, and the restored Germany joined NATO in 1990. The Warsaw Pact was dissolved by the remaining member nations in 1991.
Further Information: Appendix C: The Warsaw Pact—Soviet Union. [Online] Available http://lcweb2.loc.gov/frd/cs/soviet_union/su_appnc.html, October 25, 2000; Halsall, Paul, ed. "The Warsaw Pact, 1955." Internet Modern History Sourcebook. [Online] Available http://www.fordham.edu/halsall/mod/1955warsawpact.html, October 25, 2000; "Warsaw Pact." MSN Encarta. [Online] Available http://encarta.msn.com/index/conciseindex/47/047DE000.htm, October 25, 2000.