At present, NATO has 31 member countries. These countries, called NATO Allies, are sovereign states that come together through NATO to discuss political and security issues and make collective decisions by consensus.
Twelve countries from Europe and North America signed the North Atlantic Treaty on 4 April 1949 in Washington, D.C.
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.
NATO’s founding member countries were: 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 all 12 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:
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 In 2006, US forces were withdrawn but the defence agreement remains valid.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 structures 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 on French territory, 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 flags of Greece and Türkiye are raised alongside those of the other NATO Allies at the Ministerial Meeting in Lisbon, Portugal in February 1952.
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 (for example, Soviet support of the North Korean invasion of South Korea in 1950), extending security to south-eastern 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 Allies sign the Accession Protocol for Germany at NATO Headquarters, which was formerly located in Paris, in October 1954. Germany joined the Alliance in May of the following year.
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, finding ways of integrating the Federal Republic of Germany into western 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 Spanish flag flies alongside those of the other Allies at NATO Headquarters in Brussels shortly after Spain’s accession to the Alliance in 1982.
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 structures 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).
A military band performs at the flag-raising ceremony for Czechia, Hungary and Poland at NATO Headquarters in Brussels in March 1999.
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.
Czechia, 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 flags of all NATO Allies are paraded in front of NATO Headquarters in Brussels in April 2004 during the flag-raising ceremony marking the accession of Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia.
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.
Allied troops carry their respective national flags during the flag-raising ceremony for Albania and Croatia at NATO Headquarters in Brussels in April 2009.
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.
Montenegrin honour guards raise NATO’s and Montenegro’s flags in Podgorica, Montenegro to mark the country’s accession to NATO in June 2017. © Reuters/Stevo Vasiljevic
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 also worked with NATO in areas such as the development of emergency response capabilities and the destruction of surplus munitions.
The Accession Protocol was signed in May 2016 and Montenegro became a member of the Alliance on 5 June 2017.
North Macedonian officers raise their country’s flag at NATO Headquarters in Brussels following the country’s accession to the Alliance in March 2020.
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 peace-support operations 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.
Finnish officers raise Finland’s flag at NATO Headquarters in Brussels in April 2023. © Reuters/Johanna Geron/Pool
NATO’s cooperation with Finland began when it joined the Partnership for Peace (PfP) programme in 1994. Over the subsequent decades, Finland became one of NATO’s most active partners and a valued contributor to the Alliance’s activities, including NATO-led operations and missions in the Balkans, Afghanistan and Iraq.
Finnish cooperation with NATO was historically based on its policy of military non-alignment and a firm national political consensus. This changed in 2022, following Russia’s full-scale invasion of Ukraine.
On 18 May 2022, Finland submitted its official letter of application to become a NATO Ally, alongside Sweden. At the 2022 NATO Summit in Madrid on 29 June, Allied Leaders agreed to invite both countries to become members of NATO. Together with Sweden, Finland completed accession talks at NATO Headquarters in Brussels on 4 July, confirming its willingness and ability to meet the political, legal and military obligations and commitments of NATO membership. On 5 July, Allies signed the Accession Protocols for both countries, which then became official Invitees, attending NATO meetings as such.
Over the following months, all NATO Allies ratified Finland’s Accession Protocol according to their national procedures. Finland deposited its Instrument of Accession to the North Atlantic Treaty on 4 April 2023, becoming NATO’s 31st member country.
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