In response to NATO, Eastern European nations including Poland & the USSR signed this 1955 treaty
The original 
membership of the North Atlantic Treaty Organization (NATO) consisted of 
Belgium, Britain,... [DOC] [TLE] The Warsaw Pact is formed - May 14, 1955 - HISTORY.com [PAR] The Soviet Union and seven of its European satellites sign a treaty establishing ... 
the treaty was signed in Warsaw, included the Soviet Union, Albania, Poland, ... 
members of the North Atlantic Treaty Organization (NATO) on May 9, 1955 to ... 
eastern bloc nations, such as Poland and Czechoslovakia, throughout 1990 and
... [DOC] [TLE] Warsaw Pact - Wikipedia [PAR] The Warsaw Pact, formally the Treaty of Friendship, Co-operation, and Mutual 
Assistance and sometimes, informally, WarPac.