How did tensions between the U. S. and the USSR contribute to the development of the North Atlantic Treaty Organization (NATO), the Warsaw Pact, and the Cold War?

NATO was established as a political and military alliance in 1949 by the United States and its Western European allies. There were fears of a Soviet aggressive move toward Western Europe with the purpose to expand communism; large Soviet armies were stationed in East Germany and other Eastern European countries; Soviet influence had proved decisive to install Communists in high office in some places. In 1949, the Federal Republic of Germany was established, which caused Soviet fears and led to the creation of the German Democratic Republic (a communist state). When in 1955 the FRG was incorporated into NATO, the Soviet Union responded by creating the Warsaw Pact, the political and military alliance of the Eastern Bloc. Invasion from the West has always been a major fear in Russian security thinking, especially after WWII. Both NATO and the Warsaw Pact played an important role in the overall diplomatic and political confrontation of the Cold War between the two top players, the USA and the USSR.