nato article 5 summary

Collective defence and Article 5
Last updated: 20 Sep. 2022 13:23

The principle of collective defence is at the very heart of NATO’s founding treaty. It remains a unique and enduring principle that binds its members together, committing them to protect each other and setting a spirit of solidarity within the Alliance.

nato article 5 summary

Collective defence means that an attack against one Ally is considered as an attack against all Allies.
The principle of collective defence is enshrined in Article 5 of the Washington Treaty.
NATO invoked Article 5 for the first time in its history after the 9/11 terrorist attacks against the United States.
NATO has taken collective defence measures on several occasions, including in response to the situation in Syria and the Russian invasion of Ukraine.
NATO has standing forces on active duty that contribute to the Alliance’s collective defence efforts on a permanent basis.

A cornerstone of the Alliance

In 1949, the primary aim of the North Atlantic Treaty – NATO’s founding treaty – was to create a pact of mutual assistance to counter the risk that the Soviet Union would seek to extend its control of Eastern Europe to other parts of the continent.

Every participating country agreed that this form of solidarity was at the heart of the Treaty, effectively making Article 5 on collective defence a key component of the Alliance.

Article 5 provides that if a NATO Ally is the victim of an armed attack, each and every other member of the Alliance will consider this act of violence as an armed attack against all members and will take the actions it deems necessary to assist the Ally attacked.

“The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.

Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.”

This article is complemented by Article 6, which stipulates:

“For the purpose of Article 5, an armed attack on one or more of the Parties is deemed to include an armed attack:

The principle of providing assistance

With the invocation of Article 5, Allies can provide any form of assistance they deem necessary to respond to a situation. This is an individual obligation on each Ally and each Ally is responsible for determining what it deems necessary in the particular circumstances.

This assistance is taken forward in concert with other Allies. It is not necessarily military and depends on the material resources of each country. It is therefore left to the judgment of each individual member country to determine how it will contribute. Each country will consult with the other members, bearing in mind that the ultimate aim is to “to restore and maintain the security of the North Atlantic area”.

At the drafting of Article 5 in the late 1940s, there was consensus on the principle of mutual assistance, but fundamental disagreement on the modalities of implementing this commitment. The European participants wanted to ensure that the United States would automatically come to their assistance should one of the signatories come under attack; the United States did not want to make such a pledge and obtained that this be reflected in the wording of Article 5.

Invocation of Article 5

The 9/11 terrorist attacks.

The United States was the object of brutal terrorist attacks on 11 September 2001. The Alliance's 1999 Strategic Concept had already identified terrorism as one of the risks affecting NATO’s security. The Alliance’s response to 9/11, however, saw NATO engage actively in the fight against terrorism, launch its first operations outside the Euro-Atlantic area and begin a far-reaching transformation of its capabilities. Moreover, it led NATO to invoke Article 5 of the Washington Treaty for the very first time in its history.

An act of solidarity

On the evening of 12 September 2001, less than 24 hours after the attacks, the Allies invoked the principle of Article 5. Then NATO Secretary General Lord Robertson subsequently informed the Secretary-General of the United Nations of the Alliance's decision.

The North Atlantic Council – NATO’s principal political decision-making body – agreed that if it determined that the attack was directed from abroad against the United States, it would be regarded as an action covered by Article 5. On 2 October, once the Council had been briefed on the results of investigations into the 9/11 attacks, it determined that they were regarded as an action covered by Article 5.

By invoking Article 5, NATO members showed their solidarity toward the United States and condemned, in the strongest possible way, the terrorist attacks against the United States.

Taking action

After 9/11, there were consultations among the Allies and collective action was decided by the Council. The United States could also carry out independent actions, consistent with its rights and obligations under the United Nations Charter.

On 4 October, once it had been determined that the attacks came from abroad, NATO agreed on a package of eight measures to support the United States. On the request of the United States, it launched its first ever anti-terror operation – Eagle Assist – from mid-October 2001 to mid-May 2002. It consisted in seven NATO AWACS radar aircraft that helped patrol the skies over the United States; in total 830 crew members from 13 NATO countries flew over 360 sorties. This was the first time that NATO military assets were deployed in support of an Article 5 operation.

On 26 October, the Alliance launched its second counter-terrorism operation in response to the attacks on the United States, Active Endeavour. Elements of NATO's Standing Naval Forces were sent to patrol the Eastern Mediterranean and monitor shipping to detect and deter terrorist activity, including illegal trafficking. In March 2004, the operation was expanded to include the entire Mediterranean.

The eight measures to support the United States, as agreed by NATO were:

Enhanced collective defence measures

On the request of Türkiye, on three occasions, NATO has put collective defence measures in place: in 1991 with the deployment of Patriot missiles during the Gulf War, in 2003 with the agreement on a package of defensive measures and conduct of Operation Display Deterrence during the crisis in Iraq, and in 2012 in response to the situation in Syria with the deployment of Patriot missiles.

Since Russia’s illegal annexation of Crimea in 2014 and the rise of security challenges from the south, including brutal attacks by ISIL and other terrorist groups across several continents, NATO has implemented the biggest increase in collective defence since the Cold War. For instance, it has tripled the size of the NATO Response Force (NRF) , a highly ready and technologically advanced multinational force; established a 5,000-strong Spearhead Force within the NRF; and deployed multinational battlegroups in Estonia, Latvia, Lithuania and Poland. NATO has also increased its presence in the southeast of the Alliance, centred on a multinational brigade in Romania. The Alliance has further stepped up air policing over the Baltic and Black Sea areas and continues to develop key military capabilities, such as Joint Intelligence, Surveillance and Reconnaissance. At the Warsaw Summit in July 2016, Allies recognised cyber defence as a new operational domain, to enable better protection of networks, missions and operations; and at the meeting of foreign ministers in November 2019, Allies agreed to recognise space as a new operational domain to "allow NATO planners to make requests for Allies to provide capabilities and services, such as hours of satellite communications."

Following Russia’s unprovoked invasion of Ukraine – which started in February 2022 – and in line with its defensive planning to protect all Allies, NATO is taking additional steps to further strengthen deterrence and defence across the Alliance. This includes the deployment of the NRF for the first time in a deterrence and defence role. Allies have placed thousands of additional forces at high readiness, ensuring that the NRF continues to have the speed, responsiveness and capability to defend NATO territory and populations. Moreover, at an extraordinary Summit on 24 March 2022, NATO Leaders agreed to significantly strengthen the Alliance’s longer-term deterrence and defence posture. This was followed by a united and firm commitment of Allies, at the Madrid Summit in June 2022, to concrete measures such as deploying additional in-place combat-ready forces on the eastern flank, to be scaled up from the existing battlegroups to brigade-size units where and when required, underpinned by rapidly available reinforcements, prepositioned equipment, and enhanced command and control. They also made initial offers to NATO’s new force model, which will strengthen and modernise the NATO Force Structure and will resource a new generation of military plans. All these steps, together with the release of the 2022 Strategic Concept, which identified Russia as “the most significant and direct threat to Allies’ security and to peace and stability in the Euro-Atlantic area” will substantially strengthen NATO’s deterrence and forward defences.

Standing forces

Collective defence measures are not solely event-driven. NATO has a number of standing forces on active duty that contribute to the Alliance’s collective defence efforts on a permanent basis. These include NATO’s standing maritime forces, which are ready to act when called upon. They perform different tasks ranging from exercises to operational missions, in peacetime and in periods of crisis and conflict.

Additionally, NATO has an integrated air defence system to protect against air attacks, which also comprises the Alliance’s ballistic missile defence system. NATO also conducts several air policing missions, which are collective peacetime missions that enable NATO to detect, track and identify all violations and infringements of its airspace and to take appropriate action. As part of such missions, Allied fighter jets patrol the airspace of Allies who do not have fighter jets of their own. They run on a 24/7 basis, 365 days a year.

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Foreign Policy Research Institute

A nation must think before it acts.

Article 5 for the Next Decade of NATO

Article 5 for the Next Decade of NATO

Bottom Line

Collective defense is at the heart of European security. Enshrined within Article 5 of its founding treaty , NATO allies see “an armed attack against one or more of them in Europe or North America shall be considered an attack against them all.” Written over seventy years ago with the threat of a Soviet invasion of Western Europe in mind, Article 5 has been formally invoked just once—in support of the United States following the 9/11 terrorist attacks. Collective defense held throughout Europe and prevented open military conflict between NATO allies and the Soviet Union. In the 21st century, however, conflict can take many forms. With that in mind, it’s worth considering whether the time has come to review the text of Article 5 in light of current trends in warfare which may not be captured in the original “armed attack” language.

Since the Soviet collapse in 1991, NATO has evolved. Originally created as a defensive alliance, it has since become more active in “out of area” actions to preserve security and protect human rights, redefining the alliance’s international role. NATO deployed forces in Bosnia-Herzegovina in 1995 and Kosovo in 1999. In the early 2000s, NATO deployed forces outside of Europe for stabilization and training in Afghanistan, training in Iraq, and maritime security in the Gulf of Aden.

After Russia’s 2014 invasion of Ukraine, NATO rediscovered its essential collective defense role in Europe. Members committed to increasing defense spending and ensuring that new allies were interoperable. Russia’s escalation of its war on February 24, 2022, reinforced this need.

Ukraine’s battlefield successes against Russian ground forces, thanks in no small part to Western support for Ukrainian efforts to preserve its sovereignty, will have a lasting impact on European security. As NATO allies upgrade their defense postures, there’s an urgent need to rethink NATO as a political organization and the sort of future threats it may face.

The principal future threat to NATO members probably won’t come from artillery shells or tanks rolling across the border, but rather from cyber, biological, air, and space. And those threats will not only originate from Russia. As the European Union and individual countries in Europe recognize, China poses a threat to Europe.

The challenge for NATO then becomes how to adapt Article 5 to accommodate such longer-distance or non-territorial threats. Are additions or revisions to the NATO treaty’s diplomatic architecture necessary to properly accommodate the potential of cyberwarfare and other emerging technologies? How do non-North Atlantic countries contribute to global security?

Broader Definition of ‘Armed Attack’

The language used in the NATO treaty is very specific, saying “an armed attack” on any member will be considered an attack on all members, and that members would then would “assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.” Although Article 6 goes on to describe the sort of targets of an armed attack that would require a response, the definition of armed attack itself is treated as self-evident.

In the contemporary world, however, non-violent attacks can be devastating in their own ways. Cyber attacks, for example, are non-violent and therefore not an “armed attack,” yet could paralyze a country’s infrastructure. This could embolden rogue actors who know that this is a tool they can utilize without necessarily triggering an Article 5 response. While NATO holds annual cyber defense exercises and is clearly taking cyber threats seriously on an operational level, the alliance should pay more attention to the political and strategic implications of cyber warfare.

For example, in 2007 Estonia was hit by a ruthless cyber attack from Russia in response to the removal of a Soviet-era war monument. For three weeks, state and commercial websites ranging from defense ministries to banks and media outlets were targeted, rendering them inaccessible to the public. Estonia was even forced to close its digital borders and block all international web traffic.

At the time, this did not provoke an Article 5 response. However, the alliance has since recognized in today’s world this could be enough for an invocation. And yet, when Iran committed a cyber attack against Albania in September 2022, nothing happened despite Prime Minister Edi Rama being very open to seeing the cyber attack as a threat to collective security.

Part of the reason for NATO’s reluctance to treat cyber attacks as Article 5 matters could be that it isn’t clear what an Article 5 response to a cyber attack would look like. Policymakers struggle with the question, “and then what?” Within traditional warfare, a nation’s attack and defense posture are fairly well understood—sending tanks and missiles in support. The same cannot be said in response to cyberspace operations. Would it merit returning cyber-attacks in kind? Or a stronger, kinetic response?

This lack of clarity in the treaty will continue to create ambiguity within NATO unless it is addressed. A lot of energy is focused on improving interoperability with thirty-two allies, but making Article 5 fit for the next seventy-five years is equally important.

Member States and Allies

The other issue with Article 5 is the narrow definition of which nations the alliance will defend. As the Russian invasion of Ukraine has shown, NATO could not deter an attack on a non-member state. Yet, Russia’s attempt to destroy Ukraine displaced millions of people, disrupted energy imports, and drew non-European countries into the fight, which poses serious security risks within the North Atlantic region. To create an effective deterrent for this type of situation, NATO needs to be able to deter conflict not only for its members, but also a sub-group of “ally states” that have the potential to destabilize Europe.

For these partners, there would not be the strength of a NATO “obligation” to intervene if they were attacked, but it would be enshrined in an updated treaty where member nations will consider in good faith whether to support an ally. This would make it less important to expand NATO’s membership, but create a further deterrent layer that would impact European and North American security.

Obviously, the process of getting NATO members to align on who should be on this list of allies would be challenging. However, once it had been agreed you could go down one of two routes. Either publish the list to discourage an attack on those nations that are “with” NATO, or adopt a policy of deliberate ambiguity as a general deterrent to rogue actors to prevent mayhem on the periphery. This has the potential to grow alliance commitments, but many allies already operate outside the alliance structure in the Middle East and North Africa.

Additionally, for those member states already in the organization, a rethink on the formula for defense contributions is needed. National defense structures need to be fully integrated into a NATO structure to avoid duplication of resources, cost, and effort.

Reclaim the Security Architecture

More broadly, with Russia’s ground capabilities weakened but China’s capabilities moving beyond Northeast Asia, now is the time for a bold vision for a new global security framework. Leading international experts should get together to think through possible changes to the North Atlantic Treaty so that the alliance is fit for purpose in the 21st century. A conference on reimagining Article 5 of the treaty would focus leading geopolitical strategists from around the world on one of the most pressing challenges facing the United States and its allies.

In light of Russia’s attempt to destroy Ukraine, if the West wants to stand against territorial aggression it needs to involve non-Western power blocs within the joint defense architecture. Building on NATO’s Mediterranean Dialogue would secure the Mediterranean and link North Africa to Europe. It obviously isn’t possible to extend NATO membership to all friendly nations and nor should it be attempted. But the West, and particularly the United States, could encourage the creation of sister organizations, including a South Atlantic treaty organization; an organization in the Middle East for the Abraham Accords countries; and similar bodies in Southeast Asia and Africa for nations who share the ideal of Westphalian sovereignty.

This is an opportune moment to re-imagine international security. With a new Article 5 to reflect the modern world of warfare; the creation of a network of allies; and the building out of sister treaties globally, the United States and NATO can better protect its vision of the global world order.

The author would like to thank and acknowledge Derek Reveron , Nikolas Gvosdev , and Ronald Granieri for their advice and editorial input during the writing of this essay.

The views expressed in this article are those of the author alone and do not necessarily reflect the position of the Foreign Policy Research Institute, a non-partisan organization that seeks to publish well-argued, policy-oriented articles on American foreign policy and national security priorities.

Image: State Department (Photo by Ron Przysucha)

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NATO’s Article 5 Collective Defense Obligations, Explained

Here’s how a conflict in Europe would implicate U.S. defense obligations.

Katherine Ebright

Executive Power

NATO — the North Atlantic Treaty Organization — is an alliance of 30 European and North American countries, including the United States. Its foundational document is the North Atlantic Treaty, which sets forth NATO’s purpose and obligations: ensuring peace and security through collective defense.

NATO was formed shortly after the end of World War II, at the dawn of the Cold War. The organization’s collective defense obligations, detailed in Article 5, have been invoked only once, on behalf of the United States after 9/11. Russia’s recent invasion of Ukraine has sparked concerns that Russian President Vladimir Putin may expand the scope of the conflict to NATO members like Poland and Lithuania, triggering NATO’s collective defense obligations. Many in the public are now asking what NATO’s collective defense obligations mean for the United States.

What are a NATO member’s collective defense obligations?

Article 5 of the North Atlantic Treaty states:

The Parties agree that an armed attack against one or more of them . . . shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking . . . such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.

This language is relatively flexible. It permits each NATO member to decide for itself what action should be taken to address an armed attack on a NATO ally. It does not require any member to respond with military force, although it permits such responses as a matter of international law. A member may decide that instead of responding with force, it will send military equipment to NATO allies or impose sanctions on the aggressor.

If a NATO ally is attacked, would Article 5 authorize the president to send U.S. forces into conflict?

No. Even if a NATO ally is attacked and Article 5 is invoked, the president needs to obtain congressional authorization before sending the military into a conflict zone or otherwise using force. Article 11 of the North Atlantic Treaty explains that “its provisions [shall be] carried out by the Parties in accordance with their respective constitutional processes.” In the United States, that means securing express authorization from Congress, which has the sole constitutional power to declare war and is responsible for military appropriations and oversight.

Consider that treaties are made by the president, with the consent of the Senate. If the invocation of a collective defense treaty automatically allowed the president to use force abroad, the House would be wholly excluded from decisions about where, when, and how the country goes to war. The Senate would play a role secondary to the president. Such a scheme would violate the Constitution’s text and design, which vest “[t]he whole powers of war” in Congress, according to a foundational Supreme Court opinion .

Congress endorsed this analysis in the 1973 War Powers Resolution , a Vietnam War-era law that reaffirms the president’s obligation to seek congressional authorization before using offensive force. The War Powers Resolution states that congressional authorization to use force “shall not be inferred . . . from any treaty heretofore or hereafter ratified.”

What about the president’s inherent powers as commander in chief?

The president’s inherent powers as commander in chief would not allow the president to send the military into a conflict zone or otherwise use military force in response to an invocation of Article 5. The Constitution vests the president with the power to defend U.S. territory and citizens, even without express authorization. But it does not permit the president to use force against an adversary who poses no direct threat to the United States, as would be involved in a military campaign to assist a NATO ally.

Since the Cold War, executive branch lawyers have tried to broaden the scope of the president’s inherent powers. They have argued that the Constitution permits the president to defend not only U.S. territory and citizens but also more abstract national interests, such as the credibility and effectiveness of the United Nations. As many experts have noted, this open-ended “national interest” theory is constitutionally dubious.

Still, executive branch lawyers concede that the president cannot unilaterally commit the military to a conflict of substantial nature, scope, and duration , even if there is a strong national interest. Any military confrontation between Russia and NATO would surely be of a substantial nature, scope, and duration — and would therefore require congressional authorization. This limitation on the president’s inherent powers explains why President George W. Bush sought congressional authorization for the Afghanistan War and the Iraq War, large-scale conflicts involving ground forces.

What could Congress’s response to an invocation of Article 5 look like?

If Congress were to decide that a military response is “necessary,” Congress could declare war or, more likely, adopt a limited authorization to use force. For years, experts and advocates have agreed that any authorization to use force should specify the conflict’s purpose and geographical scope, as well as the identity of the enemy, and that it should include an expiration date. These limitations ensure that Congress reviews the authorization on a regular basis and understands where, why, and against whom U.S. forces are fighting.

Would waiting for Congress conflict with our obligations to aid our NATO allies?

No. Our NATO allies understand that legislatures play an important role in determining what kind of support is “necessary” to respond to an invocation of Article 5. After 9/11, NATO’s governing body invoked Article 5 and called upon the NATO allies to support the United States in its response to the terrorist attacks. In turn, the leaders of NATO allies like Germany asked their legislatures for permission to deploy forces. On November 16, 2001, the German Bundestag voted to commit 3,900 troops to fight in Afghanistan as a means of fulfilling its Article 5 obligations.

Moreover, Congress can act quickly in response to national security developments, and it would likely do so for any invocation of Article 5. Congress passed the 2001 Authorization for Use of Military Force, the congressional authorization to pursue those responsible for 9/11, on September 14, 2001. In 1964, it passed the Gulf of Tonkin Resolution just three days after the supposed incident that prompted President Lyndon Johnson’s request for authorization to use force in Vietnam.

What would happen if the president sent the military abroad without securing congressional authorization?

If the president were to send the military into a conflict zone without congressional authorization, Congress could invoke the War Powers Resolution. The War Powers Resolution provides that military forces operating “without a declaration of war or specific statutory authorization . . . shall be removed by the President if the Congress so directs.” Congress could also use its power over military appropriations to restrict the president’s use of funds on an unlawful war.

What does the invocation of Article 4 mean?

In February 2022, NATO members invoked Article 4 of the North Atlantic Treaty in response to Russia’s invasion of Ukraine. Article 4 permits members to call a NATO meeting when they perceive a threat to the “territorial integrity, political independence or security” of any NATO ally. The invocation of Article 4 does not trigger any collective defense obligations.

Consistent with Article 4, the leaders of each NATO member, including President Biden, convened to reaffirm their commitment to Article 5. As a result of the meeting, NATO members made “additional defensive deployments” to the easternmost allies, some of which share a border with Ukraine. NATO members did not deploy or commit to deploying forces to Ukraine.

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What is Article 5 of the NATO treaty?

Two missiles from the Ukrainian war theater struck Poland, a NATO member, on Tuesday, setting off a frenzy over the Western alliance’s mutual defense mechanism known as Article 5.

Article 5 of the North Atlantic Treaty, NATO’s founding document, says that any attack on a NATO member in Europe or North America “shall be considered an attack against them all.”

Once a member invokes the principle of collective self-defense under the treaty, NATO can come to its defense with “such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.”

But that doesn’t mean any attack on a NATO member automatically triggers a state of war.

“It’s not like a trigger mechanism. It doesn’t mean that tomorrow every single country in NATO responds with a full military invasion of Russia,” Joel Rubin, a former deputy assistant secretary of State, said.

The diplomatic nature of an Article 5 invocation is by design. It allows the alliance the necessary pause and diplomatic toolkit to respond to an aggression on its own terms.

“If you think about it, if [it’s a trigger mechanism], you’ve given Russia all control over the battlefield. They decide when there is a war. They decide whether or not we get involved. No. We have control. We have agency over what our actions are,” Rubin said.

“Article Five is an incredibly powerful diplomatic tool. So it gives options for a Polish response. That’s what it does. It gives options. It doesn’t give requirements,” Rubin said.

Reuters reported late Tuesday that NATO members are scheduled to meet Wednesday under Article 4 to investigate the incident.

That meeting’s findings could set the stage for a formal invocation of Article 5.

The missile attack in question came amid a Russian barrage against Ukraine’s energy infrastructure.

While Polish officials did not immediately confirm that missiles landed in their territory, U.S. officials said the possibly errant missiles killed two people on the Polish side of the border.

Polish Prime Minister Mateusz Morawiecki convened his security Cabinet on Tuesday to study the explosions near the Ukrainian border.

Polish and NATO authorities on Wednesday confirmed the missiles that landed in Poland were part of Ukraine’s air defense system, which was activated to counter the Russian barrage.

The missiles were presumed to be launched by Russia on Wednesday, as part of the attack on Ukrainian infrastructure.

Given the attack on its soil, Poland will first have to investigate why the Russian missiles overshot Ukraine.

“It’s quite possible that they were hitting Ukraine as much as they could. Russia’s military — they are not always precise,” Rubin said.

But the attack could also be a direct provocation or a Russian testing of the waters to gauge NATO’s resolve.

“The first step is to figure out why this happened and figure out whether it’s a beginning salvo or a test and then calibrate the response to that,” Rubin said.

Whether the missile strike was a mistake, an attack or a test, it could become the second invocation of Article 5 in NATO’s history.

The first happened on Jan. 12, 2001, when then-NATO Secretary General George Robertson informed the United Nations that NATO allies would come to the defense of the United States following the 9/11 attacks.

That Article 5 invocation led to a series of actions, ranging from intelligence sharing to diplomatic actions to direct military action, all undertaken as a response to the terrorist strike.

Under a Polish invocation, NATO would be free to design its own collective response, whether diplomatic, economic or military, under the umbrella of the principle of collective self-defense allowed by the United Nations Charter.

Updated: 11/16/2022 10:41 a.m.

Copyright 2023 Nexstar Media Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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What are Articles 4 and 5 of NATO’s founding treaty and why do they matter?

Nearly a year into Russia’s invasion of Ukraine, Eastern European countries remain worried about their own security, while allies have warned Moscow that attacking NATO members would trigger a broader, global conflict.

The United States made a “sacred commitment” to Article 5 of NATO’s founding treaty, President Biden told leaders of countries on the alliance’s eastern flank, who gathered Wednesday in Warsaw to discuss concerns about Russian aggression. “We will defend literally every inch of NATO,” he said.

NATO Secretary General Jens Stoltenberg repeated that pledge, saying members of the alliance would “protect every inch of allied territory based on our Article 5 commitment to defend the charter: One for all, and all for one.”

The treaty article means that if Russian forces were to attack Poland, for instance, that move should be treated as an attack on the United States as well. Article 4 lays out another bedrock principle of the alliance: consultation among members if one of them is under threat.

Here’s what to know about Articles 4 and 5 of the NATO charter.

One year of Russia’s war in Ukraine

Portraits of Ukraine: Every Ukrainian’s life has changed since Russia launched its full-scale invasion one year ago — in ways both big and small. They have learned to survive and support each other under extreme circumstances , in bomb shelters and hospitals, destroyed apartment complexes and ruined marketplaces. Scroll through portraits of Ukrainians reflecting on a year of loss, resilience and fear .

Battle of attrition: Over the past year, the war has morphed from a multi-front invasion that included Kyiv in the north to a conflict of attrition largely concentrated along an expanse of territory in the east and south. Follow the 600-mile front line between Ukrainian and Russian forces and take a look at where the fighting has been concentrated .

A year of living apart: Russia’s invasion, coupled with Ukraine’s martial law preventing fighting-age men from leaving the country, has forced agonizing decisions for millions of Ukrainian families about how to balance safety, duty and love , with once-intertwined lives having become unrecognizable. Here’s what a train station full of goodbyes looked like last year.

Deepening global divides: President Biden has trumpeted the reinvigorated Western alliance forged during the war as a “global coalition,” but a closer look suggests the world is far from united on issues raised by the Ukraine war . Evidence abounds that the effort to isolate Putin has failed and that sanctions haven’t stopped Russia , thanks to its oil and gas exports.

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Here’s what nato’s article 5 is and how it applies to russia’s invasion of ukraine.

Russia’s unprovoked invasion of Ukraine has prompted a roiling debate about what US involvement should look like.

US officials have made clear that American troops won’t engage directly with Russian forces, and NATO members have pushed back on calls for a no-fly zone to be set up in Ukraine, warning that it could lead to a “full-fledged war in Europe.”

The situation could change quickly, however, if Moscow’s attack on Ukraine spilled into a NATO member nation and triggered a response based on the alliance’s Article 5 principle.

But what is Article 5, and how does it apply to the ongoing war in Ukraine?

Here’s what you need to know:

What is Article 5?

Article 5 is the principle that an attack on one member of NATO is an attack on all members. It’s been a cornerstone of the 30-member alliance since it was founded in 1949 as a counterweight to the Soviet Union.

The principle aims to deter potential adversaries from attacking NATO members. Article 5 guarantees that the resources of the whole alliance can be used to protect any single member nation. This is crucial for many of the smaller countries who would be defenseless without their allies. Iceland, for example, has no standing army.

Since the US is the largest and most powerful NATO member, any state in the alliance is effectively under US protection.

According to the NATO website, Article 5 specifically lays out:

“ The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defense recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area .

Firefighters work on a fire on a building after bombings on the eastern Ukraine town of Chuguiv on February 24, 2022, as Russian armed forces are trying to invade Ukraine from several directions, using rocket systems and helicopters to attack Ukrainian position in the south, the border guard service said. - Russia's ground forces on Thursday crossed into Ukraine from several directions, Ukraine's border guard service said, hours after President Vladimir Putin announced the launch of a major offensive. Russian tanks and other heavy equipment crossed the frontier in several northern regions, as well as from the Kremlin-annexed peninsula of Crimea in the south, the agency said. (Photo by Aris Messinis / AFP) (Photo by ARIS MESSINIS/AFP via Getty Images)

What is NATO and why hasn't it imposed a no-fly zone in Ukraine?

Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security .”

During the Cold War, the main concern was the Soviet Union, but in recent years, Russia’s aggressive actions in eastern Europe have been the focus of attention.

Has Article 5 ever been invoked?

Article 5 has only been invoked once: After the September 11, 2001, terror attacks on the US.

But NATO’s Article 5 principle stretches beyond attacks on the homeland. The alliance has also taken collective defense measures on several occasions, including deploying Patriot missiles in 2012 on the Syrian-Turkish border and bolstering its forces in Estonia, Latvia, Lithuania and Poland following Russia’s annexation of Crimea in 2014.

NATO allies have also joined the US to fight in Afghanistan, Iraq and Syria.

How does Article 5 apply to Russia’s attack on Ukraine?

Since Ukraine is not a member of NATO , the US is not compelled to protect the country the same way it would if a NATO member nation was attacked.

But many of Ukraine’s neighbors are NATO members, and if a Russian attack extended into one of those countries, Article 5 could trigger direct involvement from the US and other NATO members.

What constitutes an attack on a NATO member nation?

The Article 5 language specifies that an “armed attack” on a member nation is what triggers collective action.

But what constitutes an “armed attack” is up to NATO members, and Russia’s aggressive posture has already prompted concern about the country’s willingness to potentially tempt a NATO response.

For example, Democratic Sen. Mark Warner of Virginia told The Washington Post recently that a Russian cyberattack on Ukraine could lead to consequences beyond the intended “geographic boundaries” and affect NATO members.

Russian President Vladimir Putin arrives to chair a Security Council meeting via a video link in Moscow on February 25, 2022.

Putin vs. the entire concept of international law

“It could end up bleeding into Poland or Romania or into the Baltic states and cause damage that would shut down hospitals, and potentially, you’ve got American troops there. If American troops in a truck crash because the lights were out, you could get very close to Article 5,” Warner, the Senate Intelligence Committee chairman, told the outlet.

Russia’s attack on the Zaporizhzhia nuclear power plant site – the largest in Europe – had prompted similar concern. While local authorities said there’s been “no change in radiation levels” in the area, what if there had been a radiation leak that spread into a NATO member nation?

“That’s a question for the alliance to make,” Pentagon spokesman John Kirby told CNN earlier this month . “Specifically, I would just remind that Article 5 makes it clear that it’s an armed attack on a NATO ally triggers Article 5. … But how that’s interpreted – that would be really something for the NATO alliance to determine.”

What are US officials currently saying about Article 5?

US Secretary of State Antony Blinken has reiterated the US’ and allies’ commitment to NATO’s Article 5 , stating, “If there is any aggression anywhere, on NATO territory on NATO countries, we the United States, all of our allies and partners will take action to defend every inch of NATO territory. It’s as clear and direct as that.”

The comments from the top US diplomat echoed President Joe Biden’s pledge during his State of the Union address to “defend every inch of territory of NATO countries with the full force of our collective power.”

CNN’s Jeremy Herb contributed to this report.

Summary of the North Atlantic Treaty (1949)

There are only 14 articles to the treaty, meaning it is a relatively short treaty. The purpose of the treaty is for collective defence and for the preservation of peace and security. It entered into force on the 24th August 1949.

Website of NATO . The Treaty in full can be found here

As of April 2017, NATO members are:

nato article 5 summary

Ukraine invasion — explained

The roots of Russia's invasion of Ukraine go back decades and run deep. The current conflict is more than one country taking over another; it is — in the words of one U.S. official — a shift in "the world order." Here are some helpful resources to make sense of it all.

A part of the NATO treaty could turn Russia's invasion of Ukraine into a wider war

nato article 5 summary

Secretary of Defense Lloyd Austin and Polish Defense Minister Mariusz Blaszczak stand with Polish and U.S. soldiers at the 33rd Air Base of the Polish Air Force near Powidz during a visit last week. Janek Skarzynski/AFP via Getty Images hide caption

Secretary of Defense Lloyd Austin and Polish Defense Minister Mariusz Blaszczak stand with Polish and U.S. soldiers at the 33rd Air Base of the Polish Air Force near Powidz during a visit last week.

As Russia began its invasion of Ukraine, some U.S. officials and analysts were already warning of a possible escalation of the conflict into a wider war.

The trigger: Article 5 of the North Atlantic Treaty.

As the fighting continues, we unpack what Article 5 is, what could invoke it, and the places and people to watch.

What is it?

Article 5 is a key pillar of the 1949 North Atlantic Treaty — also known as the Washington Treaty — and is based on the principle of collective defense. It means that an attack on one member of NATO is deemed to be an attack on all.

Ukraine is not a member of NATO, but a number of its neighbors are.

"There are 30 members of NATO, and we have given all of them Article 5," said Mary Elise Sarotte, a professor of history at Johns Hopkins University and author of Not One Inch: America, Russia, and the Making of Post-Cold War Stalemate .

How NATO's expansion helped drive Putin to invade Ukraine

How NATO's expansion helped drive Putin to invade Ukraine

"And I don't think Americans understand this — that means we are obligated by treaty to basically defend them or go to war if they are attacked by Russia. We are obliged to treat an attack on Estonia as if it were an attack on Chicago by treaty."

"So, if there is an Article 5 incursion, this could very quickly become not Ukraine's war, but our war."

The article states:

[NATO members] will assist the party or parties so attacked by taking forthwith, individually and in concert with the other parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.

Article 5 has been invoked once — in response to the 9/11 attacks .

Albania, Belgium, Bulgaria, Canada, Croatia, Czech Republic, Denmark, Estonia, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, Montenegro, Netherlands, North Macedonia, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Turkey, the United Kingdom, the United States

What could trigger this?

Russia has attacked Ukraine by land, sea and air – but there remains a question over cyberattacks.

Less than 24 hours after the invasion began, U.S. Senate Intelligence Committee chairman Mark Warner, D-Va., warned that if Russia launched major cyberattacks on Ukraine, the damage could spill beyond the country's borders .

Sen. Warner says a direct NATO-Russia conflict would be 'uncharted territory'

National Security

Sen. warner says a direct nato-russia conflict would be 'uncharted territory'.

"When you launch cyberattacks, they don't recognize geographic boundaries. Some of that cyberattack could actually start shutting down systems in eastern Poland," he said.

"If you shut down Polish hospitals because they can't get power to take care of their people, you're rapidly approaching what could be viewed as an Article 5 violation of NATO ... so we are in an uncharted territory."

Retired U.S. Navy Adm. James Foggo echoed this sentiment shortly after the attack began, saying the U.S. was right to station troops in Poland.

"We're doing that because we do not want the spillover effects to impact any of our NATO allies," he said. "If there is an interaction — a kinetic interaction, a fight — between Russian troops and American troops it could trigger a world war. So, we need to reinforce our allies and make sure that this crisis is contained just to Ukraine and continue to support Ukraine with lethal weapons."

Want to support the people in Ukraine? Here's how you can help

Want to support the people in Ukraine? Here's how you can help

The countries that could be affected.

It's unclear whether a traditional armed conflict will go beyond Ukraine and Russia and trigger it again. But Sarotte said there were particular places to watch.

"We're going to see, I think, regime change and we're also going to see [Russian President Vladimir Putin] take control of more areas. I think he's de facto already taken control of Belarus," she said.

"Then there is a question about does he try to do something to the Baltics, which also used to be part of the former Soviet Union. And that's really dangerous because the Baltics are in NATO."

nato article 5 summary

Soldiers of an airborne brigade of the U.S. Army stand at the Adazi Military Base of the Latvian armed forces in upon arrival Friday for their mission to strengthen the NATO presence in the region. Gints Ivuskans/AFP via Getty Images hide caption

Soldiers of an airborne brigade of the U.S. Army stand at the Adazi Military Base of the Latvian armed forces in upon arrival Friday for their mission to strengthen the NATO presence in the region.

On Friday, NATO leaders issued a scathing condemnation of Russia after meeting to discuss the invasion of Ukraine, calling the attack "the gravest threat to Euro-Atlantic security in decades."

The alliance said it was now taking "significant additional defensive deployments of forces" to its eastern flank and said it would give "political and practical support" to Ukraine.

In a statement on Thursday , it said: "Our commitment to Article 5 of the Washington Treaty is iron-clad. We stand united to protect and defend all allies."

Alejandra Marquez Janse and Ayesha Rascoe contributed to this report.

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COMMENTS

Topic: Collective defence and Article 5
Article 5 provides that if a NATO Ally is the victim of an armed attack, each and every other member of the Alliance will consider this act of
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Article 5 is the cornerstone of the North Atlantic Treaty Organization (NATO) and states that an attack on one member of NATO is an attack
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What are a NATO member's collective defense obligations? ... Article 5 of the North Atlantic Treaty states: The Parties agree that an armed attack
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Article 5 of the North Atlantic Treaty, NATO's founding document, says that any attack on a NATO member in Europe or North America “shall be
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Article 5 states that the parties to the NATO treaty “agree that an armed attack against one or more of them in Europe or North America shall be
North Atlantic Treaty
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
Here's what NATO's Article 5 is and how it applies to Russia's ...
Article 5 is the principle that an attack on one member of NATO is an attack on all members. It's been a cornerstone of the 30-member
Summary of the North Atlantic Treaty (1949)
Article 5 – The parties agree that an armed attack on any party is an attack on them all. If such armed attack does incur, following Article 51 of the UN
How NATO's Article 5 could escalate the Russia-Ukraine conflict
Article 5 of the North Atlantic Treaty means that an attack on one member state is determined to be an attack on all. Ukraine is not part of