NATO was created by 12 countries and Article 10 governs how others join

Background

NATO was created by 12 countries from Europe and North America on 4 April 1949. Since then, 20 more countries have joined through 10 rounds of enlargement, and NATO has 32 member countries, called Allies, that take decisions by consensus. Article 10 of the North Atlantic Treaty sets out how countries can join: membership is open to any European State in a position to further the principles of the Treaty and to contribute to the security of the North Atlantic area. Any decision to invite a country is taken by the North Atlantic Council, NATO's principal political decision-making body.