After its formation in 1949 with twelve founding members, NATO grew by including Greece and Turkey in 1952 and West Germany in 1955, and then later Spain in 1982.
After the Cold War ended, and Germany reunited in 1990, there was a debate in NATO about continued expansion eastward. In 1999, Poland, Hungary, and the Czech Republic joined NATO, amid much debate within the organization and Russian opposition.
Another expansion came with the accession of seven Central and Eastern European countries: Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia. These nations were first invited to start talks of membership during the 2002 Prague summit, and officially joined NATO Mar 29th 2004.
