What was the Warsaw pact? The Warsaw fact was a military alliance between all of the communist east European countries, headed by the Soviet Union in 1955. It was designed as a response to NATO. Members were to support each other if attacked.
The Soviet Union formed this alliance as a counterbalance to the North Atlantic Treaty Organization (NATO), a collective security alliance concluded between the United States, Canada and Western European nations in 1949. The Warsaw Pact supplemented existing agreements.