In addition to the original 12 member countries who created the Alliance on 4 April 1949, the following countries joined NATO:
- on 18 February 1952, Greece and Turkey;
- on 6 May 1955, the Federal Republic of Germany;
- on 30 May 1982, Spain;
- on 12 March 1999, the Czech Republic, Hungary and Poland
- on 29 March 2004, Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia;
- on 1 April 2009, Albania and Croatia.
