NATO

The North Atlantic Treaty Organization, or NATO, is a political and military alliance of 32 countries from Europe and North America whose members have pledged to defend one another. It was created by the North Atlantic Treaty, signed in Washington, D.C., on 4 April 1949. Its members, called Allies, take decisions by consensus.

History of NATO

Twelve countries signed the North Atlantic Treaty on 4 April 1949: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States. The timing reflected the early Cold War. The Soviet Union had drawn an Iron Curtain across Europe and dominated its neighbors in the center and east, while the founders were still rebuilding after World War II. They agreed that pooling their strength was the way to deter the Soviet threat.

The treaty is only 14 articles long, just over 1,000 words, and it has never needed to be modified. Its authority comes from Article 51 of the United Nations Charter, which recognizes the inherent right of states to individual or collective self-defense.

Membership has grown through ten rounds of enlargement, in 1952, 1955, 1982, 1999, 2004, 2009, 2017, 2020, 2023 and 2024. Twenty countries joined after the founding. Sweden became the 32nd member on 7 March 2024. Under Article 10, 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, and the North Atlantic Council decides on invitations by consensus.

Structure and headquarters

The North Atlantic Council is NATO’s principal political decision-making body, and it meets at the organization’s headquarters in Brussels. The site also houses the national delegations of member countries and the liaison offices or diplomatic missions of partner countries. About 4,000 people work there full time, including roughly 2,000 in national delegations and supporting staff, 1,000 civilian members of the International Staff and agencies, 500 in the International Military Staff and about 300 at partner missions. The headquarters hosts around 6,000 meetings a year.

The organization has moved several times. It began in London at 13 Belgrave Square in 1949, relocated to Paris in April 1952 and moved to Brussels after France withdrew from the integrated military command structure in 1966. The Brussels site was built in six months and inaugurated on 16 October 1967.

What NATO does

Collective defense is the core task. Article 5 commits Allies to assist one another if one is attacked. The help may or may not involve armed force, and it can include any action an Ally considers necessary to restore and maintain the security of the North Atlantic area. NATO invoked Article 5 for the first and only time after the terrorist attacks on the United States on 11 September 2001.

Article 5 also supports everyday activity. It underpins deterrence and defense, including regular military exercises and the deployment of standing forces, and NATO describes its approach as protecting against all threats from all directions. NATO has run exercises since 1951. They take three forms: live exercises with forces in the field, command-post exercises for headquarters and staffs, and exercise studies such as map exercises or war games. Their purpose is to prepare commands for operations and to help forces from different countries work together despite differences in doctrine, language and equipment.

NATO vs. the European Union

The two organizations are separate. NATO is an intergovernmental security alliance created in 1949, while the European Union is a union of 27 member states that was built on economic integration and now makes common rules in many policy fields. The EU’s own history page notes that by 2020 NATO had 30 members, including 21 EU countries.

Membership therefore overlaps without matching. Canada, Iceland, Norway, Türkiye, the United Kingdom and the United States belong to NATO but not to the EU, and some EU members are not in NATO. Both bodies take decisions by agreement among their member governments, though the EU adds common institutions such as a directly elected parliament.

Funding and defense spending

NATO is resourced through direct and indirect contributions from its members. Common funds come from direct contributions to collective budgets and programs and amount to around 4.6 billion euros for 2025, rising to as much as 5.3 billion euros for 2026. There are three main common-funded budgets: the Civil Budget, which funds the headquarters, the Military Budget, which funds the command structure, and the NATO Security Investment Programme. All Allies share the cost through a formula based on gross national income.

National contributions are the largest part of the total, since each country pays for the forces and capabilities it can make available to the alliance. NATO reports that European Allies and Canada raised defense spending by more than 90 billion dollars in 2025, in 2021 prices, a rise of nearly 20 percent on 2024. Their combined spending went from 1.4 percent of gross domestic product in 2014 to 2.3 percent in 2025, a total of more than 571 billion dollars in 2021 prices.

Criticism and challenges

Burden-sharing is the recurring issue. NATO’s own spending guidance says that in many cases expenditure beyond 2 percent of GDP is needed to remedy existing shortfalls across all domains, and the Allies made a 2025 commitment to invest 5 percent of GDP by 2035. NATO says it will review the trajectory and balance of this plan in 2029. Because spending is national and the common budget is small by comparison, differences between countries in what they spend and what they can field remain a standing point of debate among the Allies.

Legacy and impact

NATO has grown from 12 members to 32 while keeping its original treaty text. Its founding promise of mutual assistance remains the core of the transatlantic relationship, and the organization says Article 5 underpins all of its other work on deterrence and defense.

Editorially reviewed by Specialty Digest Editorial TeamLast reviewed November 4, 2026Researched and drafted with AI assistanceReport an issue