North Atlantic Treaty


The North Atlantic Treaty, also known as the Washington Treaty, forms the legal basis of, and is implemented by, the North Atlantic Treaty Organization. The treaty was signed in Washington, D.C., on 4 April 1949.

Background

The treaty was signed in Washington, D.C., on 4 April 1949 by a committee which was chaired by US diplomat Theodore Achilles. Earlier secret talks had been held at the Pentagon between 22 March and 1 April 1948, of which Achilles said:
The talks lasted about two weeks and by the time they finished, it had been secretly agreed that there would be a treaty, and I had a draft of one in the bottom drawer of my safe. It was never shown to anyone except Jack . I wish I had kept it, but when I left the Department in 1950, I dutifully left it in the safe and I have never been able to trace it in the archives. It drew heavily on the Rio Treaty, and a bit of the Brussels Treaty, which had not yet been signed, but of which we were being kept heavily supplied with drafts. The eventual North Atlantic Treaty had the general form, and a good bit of the language of my first draft, but with a number of important differences.

According to Achilles, another important author of the treaty was John D. Hickerson:
More than any human being Jack was responsible for the nature, content, and form of the Treaty...It was a one-man Hickerson treaty.

As a fundamental component of NATO, the North Atlantic Treaty is a product of the US' desire to avoid overextension at the end of World War II, and consequently pursue multilateralism in Europe. It is part of the US' collective defense arrangement with Western European powers, following a long and deliberative process. The treaty was created with an armed attack by the Soviet Union against Western Europe in mind, although the mutual self-defense clause was never invoked during the Cold War.
By signing the North Atlantic Treaty, parties are "determined to safeguard the freedom, common heritage and civilization of the peoples, founded on the principles of democracy, individual liberty and the rule of law."

Members

Founding members

The following twelve states signed the treaty and thus became the founding members of NATO. The following leaders signed the agreement as plenipotentiaries of their countries in Washington, D.C., on 4 April 1949:
The following four states joined the treaty after the 12 founding states, but before the dissolution of the Soviet Union:

Members who joined after the dissolution of the Soviet Union

The following 16 states joined the treaty after the dissolution of the Soviet Union:

Withdrawal

No state has rescinded its membership, but some dependencies and jurisdictions of member states that had prior NATO mutual defense protection under Article 6 have not requested membership after becoming independent or handed over to non-NATO states, e.g.:

Provisions

Article 1

Article 1 of the treaty states that member parties "settle any international disputes in which they may be involved by peaceful means in such a manner that international peace and security, and justice, are not endangered, and to refrain in their international relations from the threat or use of force in any manner inconsistent with the purposes of the United Nations."
Members seek to promote stability and well-being in the North Atlantic area through preservation of peace and security in accordance with the Charter of the United Nations.

Article 2

Article 2 of the treaty stipulates that "The Parties will contribute toward the further development of peaceful and friendly international relations by strengthening their free institutions, by bringing about a better understanding of the principles upon which these institutions are founded, and by promoting conditions of stability and well-being. They will seek to eliminate conflict in their international economic policies and will encourage economic collaboration between any or all of them." This is sometimes referred to as the Canada Clause after Pearson pushed for its inclusion in the treaty. This included proposals for a trade council, cultural program, technological sharing, and an information program. Of those, only the latter two were passed. Nonetheless, it has been brought up by observers commenting on trade disputes between members.

Article 3

Article 3 of the treaty states that "In order more effectively to achieve the objectives of this Treaty, the Parties, separately and jointly, by means of continuous and effective self-help and mutual aid, will maintain and develop their individual and collective capacity to resist armed attack."
This was interpreted in 2022 as the basis for the target for a 2% GDP expenditure rule, which was established as a loose guideline in 2006. This metric was confirmed again during the 2014 Wales summit.
It has also been used as a core concept for a mandate to strengthen member resilience: the ability to resist and recover from major disasters, failures in infrastructure, or traditional armed attack. This commitment was first accepted during the 2016 Warsaw summit, and further reiterated and clarified due to the COVID-19 pandemic in 2021. In accordance with NATO documents, this has been understood to include seven key areas:
  • Continuity of government during a crisis
  • Energy and power grid infrastructure resilience
  • Immigration control
  • Food and water security
  • Medical emergencies
  • Resilient civil communications
  • Effective transportation networks

    Article 4

Article 4 is generally considered the starting point for major NATO operations, and therefore is intended for either emergencies or situations of urgency. It officially calls for consultation over military matters when "the territorial integrity, political independence or security of any of the parties is threatened." Upon its invocation, the issue is discussed in the North Atlantic Council, and can formally lead into a joint decision or action on behalf of the Alliance.

Invocations

It has been invoked nine times as of 19 September 2025.
NationsDateReasonOutcome
Turkey

Threatened invocations

There have also been instances where Article 4 was not formally invoked, but instead threatened. In fact, this was viewed as one of the original intentions for Article 4: as a means to elevate issues and provide member nations a means of deterrence. For example, in November 2021, the Polish foreign ministry—along with Estonia, Lithuania, and Latvia—briefly considered triggering Article 4 due to the Belarusian migrant crisis, but it was not formally requested. On 28 December 2024, Swedish member of parliament and former minister of defense, Peter Hultqvist wanted the government to activate Article 4 in response to the 2024 Baltic Sea submarine cable disruptions and in September 2025, Denmark also considered it after unauthorised drone flights over airports and military bases in the country.

Article 5

The key section of the treaty is Article 5. Its commitment clause defines the casus foederis. It commits each member state to consider an armed attack against one member state, in the areas defined by Article 6, to be an armed attack against them all. Upon such attack, each member state is to assist by taking "such action as deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area." The article has only been invoked once, but considered in a number of other cases.

Invocations

September 11 attacks
Article 5 has been invoked only once in NATO history, after the September 11 attacks on the United States in 2001. Following the September 11 attacks, the Secretary General of NATO, George Robertson telephoned Colin Powell and said that declaring an Article 5 contingency would be a useful political statement for NATO to make. The United States indicated it had no interest in making such a request itself; however, it would not object to the council taking such action on its own.

Threatened invocations

Article 6

Article 6 states that Article 5 covers only member states' territories in Europe, North America, Turkey, and islands in the Atlantic north of the Tropic of Cancer.
A clarification regarding the territories to which Article 5 applies was issued by Article 2 of the Protocol to the North Atlantic Treaty on the accession of Greece and Turkey signed on 22 October 1951. Subsequent expansions, such as to West Germany in 1955, were treated in the same way. A further clarification was made in a NAC meeting on July 3, 1962 that Algeria was no longer included.
In 1954, following India's annexation of Dadra and Nagar Haveli, the Portuguese government was precluded from invoking Article 5 due to Article 6, but it was understood at the time that Article 4 could be invoked.
It was the opinion in August 1965 of the US State Department, the US Defense Department, and the legal division of NATO that an attack on the North Pacific U.S. island state of Hawaii would not trigger the treaty, but an attack on the other 49 would. The Aleutian Islands in the North Pacific are not treated in the same manner by NATO as Hawaii is, since they are politically part of Alaska rather than their own state like Hawaii, and considered geographically part of North America, while Hawaii is not. Similarly, Mediterranean islands like Sicily, Corsica, the Baleares, etc. are considered geographically part of Europe, and therefore under Article 6. However, even though islands like Puerto Rico are considered part of North America, they do not fall under NATO because specifically those islands that are in the Atlantic have to be north of the Tropic of Cancer. The Spanish cities of Ceuta and Melilla on the North African shore are not under NATO protection in spite of Moroccan claims to them. Legal experts have interpreted that other articles could cover the Spanish North African cities but this take has not been tested in practice. This is also why events such as the Balyun airstrikes did not trigger Article 5, as the Turkish troops that were attacked were in Syria, not Turkey. As well as why the 1982 invasion of the Falkland Islands by Argentina did not trigger Article 5, as the Falkland Islands are in the South Atlantic, south of the Tropic of Cancer, and not within the geographic area covered by Article 6.
On 16 April 2003, NATO agreed to take command of the International Security Assistance Force in Afghanistan, which includes troops from 42 countries. The decision came at the request of Germany and the Netherlands, the two states leading ISAF at the time of the agreement, and all nineteen NATO ambassadors approved it unanimously. The handover of control to NATO took place on 11 August, and marked the first time in NATO's history that it took charge of a mission outside of the area delineated by Article 6.