The original twelve members of NATO in 1949 were the United States, the United Kingdom, Canada, France, Denmark, Iceland, Italy, Norway, Portugal, Belgium, Netherlands, and Luxembourg.
In 1952, Greece and Turkey joined. West Germany was admitted in 1955 and in 1982 Spain became the sixteenth member.
On March 12, 1999, three new countries - the Czech Republic, Hungary, and Poland - brought the total number of NATO members to 19.
On April 2, 2004, seven new countries joined the alliance. These countries are Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia.
The two newest countries that joined as NATO members on April 1, 2009 are Albania and Croatia.
To retaliate against the formation of NATO, in 1955 the Communist countries banded together to form the now-defunct Warsaw Pact, which originally consisted of the Soviet Union, Albania, Bulgaria, Czechoslovakia, Hungary, East Germany, Poland, and Romania. The Warsaw Pact ended in 1991, with the fall of Communism and the dissolution of the Soviet Union.
Most notably, Russia remains a non-member of NATO. Interestingly enough, in the military structure of NATO, a U.S. military officer is always commander-in-chief of NATO forces so that U.S. troops never come under control of a foreign power.
The 28 Current NATO MembersAlbania