What was the name of the military alliance formed to counter Soviet expansion?
Introduction. In 1949, the prospect of further Communist expansion prompted the United States and 11 other Western nations to form the North Atlantic Treaty Organization (NATO). The Soviet Union and its affiliated Communist nations in Eastern Europe founded a rival alliance, the Warsaw Pact, in 1955.est Germany formally joined NATO on May 5, 1955, and the Warsaw Pact was signed less than two weeks later, on May 14. Joining the USSR in the alliance were Albania, Bulgaria, Czechoslovakia, the German Democratic Republic (East Germany), Hungary, Poland and Romania.