At present, NATO has 30 members. In 1949, there were 12 founding members of the Alliance: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States. The other member countries are: Greece and Türkiye (1952), Germany (1955), Spain (1982), the Czech Republic, Hungary and Poland (1999), Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia (2004), Albania and Croatia (2009), Montenegro (2017) and North Macedonia (2020).
- Provision for enlargement is given by Article 10 of the North Atlantic Treaty.
- Article 10 states that membership is open to any “European State in a position to further the principles of this Treaty and to contribute to the security of the North Atlantic area”.
- Any decision to invite a country to join the Alliance is taken by the North Atlantic Council, NATO’s principal political decision-making body, on the basis of consensus among all Allies.
The founding members
On 4 April 1949, the foreign ministers from 12 countries signed the North Atlantic Treaty (also known as the Washington Treaty) at the Departmental Auditorium in Washington, D.C.: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States.
Within the five months following the signing ceremony, the Treaty was ratified by the parliaments of the interested countries, sealing their membership.
The 12 signatories
Some of the foreign ministers who signed the Treaty were heavily involved in NATO’s work at a later stage in their careers:
- Belgium: M. Paul-Henri Spaak (NATO Secretary General, 1957-1961);
- Canada: Mr Lester B. Pearson (negotiated the Treaty and was one of the “Three Wise Men”, who drafted the report on non-military cooperation in NATO, published in 1956 in the wake of the Suez Crisis);
- Denmark: Mr Gustav Rasmussen;
- France: M. Robert Schuman (architect of the European institutions, who also initiated the idea of a European Defence Community);
- Iceland: Mr Bjarni Benediktsson;
- Italy: Count Carlo Sforza;
- Luxembourg: M. Joseph Bech;
- the Netherlands: Dr D.U. Stikker (NATO Secretary General, 1961-1964);
- Norway: Mr Halvard M. Lange (one of the “Three Wise Men”, who drafted the report on non-military cooperation in NATO);
- Portugal: Dr José Caeiro da Matta;
- the United Kingdom: Mr Ernest Bevin (main drive behind the creation of NATO and as Foreign Secretary from 1945 to 1951, he attended the first formative meetings of the North Atlantic Council);
- the United States: Mr Dean Acheson (as US Secretary of State from 1949 to 1953, he attended and chaired meetings of the North Atlantic Council).
Flexibility of NATO membership
On signing the Treaty, countries voluntarily commit themselves to participating in the political consultations and military activities of the Organization. Although each and every signatory to the North Atlantic Treaty is subject to the obligations of the Treaty, there remains a certain degree of flexibility which allows members to choose how they participate. The memberships of Iceland and France, for instance, illustrate this point.
When Iceland signed the Treaty in 1949, it did not have – and still does not have – armed forces. There is no legal impediment to forming them, but Iceland has chosen not to have any. However, Iceland has a Coast Guard, national police forces, an air defence system and a voluntary expeditionary peacekeeping force. Since 1951, Iceland has also benefitted from a long-standing bilateral defence agreement with the United States. In 2006, US forces were withdrawn but the defence agreement remains valid. Since 2008, air policing has been conducted on a periodic basis by NATO Allies.
In 1966, President Charles de Gaulle decided to withdraw France from NATO’s integrated military structure. This reflected the desire for greater military independence, particularly vis-à-vis the United States, and the refusal to integrate France’s nuclear deterrent or accept any form of control over its armed forces.
In practical terms, while France still fully participated in the political instances of the Organization, it was no longer represented on certain committees, for instance, the Defence Planning Committee and the Nuclear Planning Group. This decision also led to the removal of French forces from NATO commands and foreign forces from French territory. The stationing of foreign weapons, including nuclear weapons, was also banned. NATO’s political headquarters (based in Paris since 1952), as well as the Supreme Headquarters Allied Powers Europe or SHAPE (in Rocquencourt since 1951) moved to Belgium.
Despite France’s withdrawal from NATO’s integrated military structure, two technical agreements were signed with the Alliance, setting out procedures in the event of Soviet aggression. Since the fall of the Berlin Wall in 1989, France has regularly contributed troops to NATO’s military operations, making it one of the largest troop-contributing states. It is also NATO’s fourth-biggest contributor to the military budget.
From the early 1990s onwards, France distanced itself from the 1966 decision with, for instance, its participation at the meetings of defence ministers from 1994 (Seville) onwards and the presence of French officers in Allied Command Operations and Allied Command Transformation structures from 2003. At NATO’s Strasbourg/Kehl Summit in April 2009, France officially announced its decision to fully participate in NATO structures¹.
The accession of Greece and Türkiye
Three years after the signing of the Washington Treaty, on 18 February 1952, Greece and Türkiye joined NATO. This enabled NATO to reinforce its “southern flank”.
At a time when there was a fear of communist expansion throughout Europe and other parts of the world (Soviet support of the North Korean invasion of South Korea in 1950), extending security to southeastern Europe was strategically important. Not only did NATO membership curb communist influence in Greece – a country recovering from civil war – but it also relieved Türkiye from Soviet pressure for access to key strategic maritime routes.
The accession of Germany
Germany became a NATO member on 6 May 1955. This was the result of several years of deliberations among western leaders and Germany, whose population opposed any form of rearmament.
Following the end of the Second World War, ways of integrating the Federal Republic of Germany into west European defence structures was a priority. The Federal Republic of Germany - or West Germany - was created in 1949 and although the new state was anchored to the west, its potential was feared. Initially, France proposed the creation of a European Defence Community – a European solution to the German question. However, the French Senate opposed the plan and the proposal fell through leaving NATO membership as the only viable solution. Three conditions needed to be fulfilled before this could happen: post-war victors (France, the United Kingdom, the United States and the Soviet Union) had to end the occupation of the Federal Republic of Germany; Italy and West Germany needed to be admitted to the Western Union Defence Organisation (the military agency of the Western Union) and then there was the accession procedure itself.
When Germany joined the Western Union, the latter changed its name to become the Western European Union. This accession, together with the termination of the Federal Republic of Germany’s status as an occupied country, was bringing the country closer to NATO membership. The Federal Republic of Germany officially joined the Western Union on 23 October 1954 and its status as an occupied country came to an end when the Bonn-Paris conventions came into effect on 5 May 1955. The next day, it became NATO’s 15th member country.
With the reunification of Germany on 3 October 1990, the Länder of the former German Democratic Republic joined the Federal Republic of Germany in its membership of NATO.
The accession of Spain
Spain joined the Alliance on 30 May 1982 despite considerable public opposition. The end of Franco’s dictatorship in 1975, the military coup in 1981 and the rise of the Socialist Party (PSOE), the leading opposition party which was initially against NATO accession, made for a difficult social and political context, both nationally and internationally.
Spain fully participated in the political instances of the Organization, but refrained from participating in the integrated military structure - a position it reaffirmed in a referendum held in 1986. With regard to the military aspects, it was present as an observer on the Nuclear Planning Group; reserved its position on participation in the integrated communication system; maintained Spanish forces under Spanish command and did not accept to have troops deployed outside of Spain for long periods of time. Nevertheless, Spanish forces would still be able to operate with other NATO forces in an emergency.
Spain’s reservations gradually diminished. The Spanish Parliament endorsed the country’s participation in the integrated military command structure in 1996, a decision that coincided with the nomination of Dr Javier Solana as NATO’s first Spanish Secretary General (1995-1999).
The first wave of post-Cold War enlargement
The fall of the Berlin Wall and the dissolution of the Warsaw Pact after the end of the Cold War opened up the possibility of further NATO enlargement. Some of the new democracies of Central and Eastern Europe were eager to become integrated into Euro-Atlantic institutions.
In 1995, the Alliance carried out and published the results of a Study on NATO Enlargement that considered the merits of admitting new members and how they should be brought in. It concluded that the end of the Cold War provided a unique opportunity to build improved security in the entire Euro-Atlantic area and that NATO enlargement would contribute to enhanced stability and security for all.
The Czech Republic, Hungary and Poland were invited to begin accession talks at the Alliance’s Madrid Summit in 1997 and on 12 March 1999 they became the first former members of the Warsaw Pact to join NATO.
Drawing heavily on the experience gained during this accession process, NATO launched the Membership Action Plan - or MAP - at the Washington Summit in April 1999. The MAP was established to help countries aspiring to NATO membership in their preparations, even if it did not pre-judge any decisions.
The second wave of post-Cold War enlargement
Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia were invited to begin accession talks at the Alliance’s Prague Summit in 2002. On 29 March 2004, they officially became members of the Alliance, making this the largest wave of enlargement in NATO history.
All seven countries had participated in the MAP before acceding to NATO.
The accession of Albania and Croatia
When they were partners, Albania and Croatia worked with NATO in a wide range of areas, with particular emphasis on defence and security sector reform, as well as support for wider democratic and institutional reform.
Albania had participated in the MAP since its inception in 1999 and Croatia joined in 2002. In July 2008, they both signed Accession Protocols and became official members of the Alliance on 1 April 2009.
Shortly after regaining its independence in June 2006, Montenegro joined the Partnership for Peace in December of the same year and the Membership Action Plan three years later. It actively supported the NATO-led operation in Afghanistan from 2010 and, provided support to the follow-on mission. Developing the interoperability of its forces and pursuing defence and security sector reforms were an important part of the country’s cooperation with NATO before it became a member country. It worked with NATO in areas such as the development of emergency response capabilities and the destruction of surplus munitions – an area in which a project is still ongoing.
The Accession Protocol was signed in May 2016 and Montenegro became a member of the Alliance on 5 June 2017.
North Macedonia – the most recent accession
North Macedonia became independent in 1991 and joined NATO’s Partnership for Peace (PfP) programme in 1995 and the Membership Action Plan in 1999. For a short period between 2001 and 2003 and on the request of Skopje, NATO conducted three operations, which helped to quell tensions in the country. Before becoming a member of the Alliance, North Macedonia cooperated with NATO in key areas such as democratic, institutional, security sector and defence reforms. It also reinforced its civil preparedness capabilities through practical cooperation with NATO and actively supported the NATO-led operation in Afghanistan.
The major stumbling block to membership of the Alliance was the issue of the country’s name. A historic agreement was struck between Athens and Skopje in 2018, resolving this issue. The Prespa Agreement enabled NATO to invite Skopje to begin accession talks to join the Organization, while encouraging the government to continue implementing reforms. On 15 February 2019, the country which was previously known as the former Yugoslav Republic of Macedonia was officially recognised as the Republic of North Macedonia. On 27 March 2020, it became NATO’s 30th member.
- However, France has chosen not to become a member of NATO's Nuclear Planning Group.