The September 11, 2001 attack on the US remains the only time NATOs article 5 has been invoked. But during the existence of article 5 has any NATO country suffered a significant qualifying attack (see article 6) without it being invoked?

Politics can certainly muddy the water here and fiddle with the meaning of what constitutes an attack so I'll ask that two categories be considered when defining "an attack":

  1. The actual language in the treaty
  2. The attacked NATO country requested that article 5 be invoked

This means answers may include both requests for invocation that failed and qualifying attacks that didn't produce a request.

But essentially what I want to know is, after all this time, what explains article 5 only being invoked once: a failure to honor the treaty or 73 years of peace?

  • Comments are not for extended discussion; this conversation has been moved to chat.
    – JJJ
    Commented May 6, 2022 at 3:36
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    In this time where everyone thinks about invading someone it seems surprising how "peaceful" this post of the world was in the last 70 years. Commented May 6, 2022 at 5:00
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    The article 5 section of the Wikipedia page about the North Atlantic treaty mentions that in 2015 Turkey considered briefly incoming article 5 after the downing of one of their jets somewhere between Turkey and Syria, but didn't. So maybe not that serious. Commented May 6, 2022 at 5:20
  • If you consider 9/11 to be a valid invocation, there have been many other terrorist attacks on Nato members from groups with connections from Libya to Ireland to East Germany (the RAF in Germany, Irish terrorists in the UK, Arab terrorists across Europe, etc). IMO it's not clear if they count as Article 5 attacks, so the question needs to make it clear.
    – Stuart F
    Commented Jun 29, 2023 at 9:17

5 Answers 5


As it was generally understood, the 'armed attack' in Article 5 refers to inter-state warfare. But it does not say so, and it got used after 9/11 as a political signal. There were many terrorist incidents involving NATO members:

  • The IRA attacked the UK (NATO member) from bases in the Republic of Ireland (not a member). It was not in the interest of the UK government to invade the ROI over this.
  • The domestic Red Army Faction attacked West Germany (NATO member) with support from Communist intelligence agencies (not NATO members). Again, it was not in the interest of the West German government to invade the GDR government over this.
  • Palestinian groups based in the Middle East attacked the Olympic Games in Germany (NATO member). Again, it was not in the interest of the West German government to declare a war. (They were busy explaining their inept counterterrorist operations ...)

Another category would be border incidents. From the long list:

  • The Soviets shot Turkish border guards (Turkey is a NATO member).
  • In 1950, the Soviets destroyed a US aircraft over the Baltic. According to the US, not in Soviet airspace.
  • Syrian fighting spilled into Turkey.

Again, it was not in the interest of NATO to turn those incidents into a war. Perhaps because there were spy overflights by the US and UK which did deliberately violate Soviet airspace.

My conclusion: Article 5 successfully deterred major interstate war. That was not "luck," it was the knowledge that a fight between the Cold War blocks could quickly spiral out of control. I don't know how old you are, but I grew up in the knowledge that if "the war" came, a large part of mankind would die. Both sides were interested in keeping a sense of perspective, rather than fiat iustitia, et pereat mundus as an emperor said four centuries earlier.

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    The plane that was shot down in 1950 was either in Soviet airspace or over international waters, so it would not fall under article 5.
    – phoog
    Commented May 6, 2022 at 8:54
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    @phoog: actually it might, because article 5 includes an attack on the armed forces of the signatories in Europe. It doesn't have to be on the territory of the signatories. Some seas like the Mediterranean are explicitly included in article 6. The Baltic isn't so, but it's considered in Europe. Airplanes are specifically included as well in article 6. Commented May 6, 2022 at 12:56
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    @Fizz attacks on forces trigger article five not if they are anywhere in Europe but only if they are in or over "any other area in Europe in which occupation forces of any of the Parties were stationed on the date when the Treaty entered into force or the Mediterranean Sea or the North Atlantic area north of the Tropic of Cancer." The Baltic Sea does not qualify except for territorial waters of NATO members or of occupied territories (i.e. in West German territorial waters).
    – phoog
    Commented May 6, 2022 at 14:20
  • @phoog: well, if you're certain, you can get some points by writing that as an answer to my Q: politics.stackexchange.com/questions/72992/… Commented May 6, 2022 at 14:21
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    @Acccumulation Turkey's territory is explicitly included in the scope of the treaty, including those portions that are not part of Europe.
    – phoog
    Commented May 9, 2022 at 14:52

As mentioned in o.m. answers conclusion: The Noth Atlantic Treaty seems to have successfully deterred major warfare in the last 73 years. The only occurrence where another country openly attacked a NATO member was during the Falkland war, though the treaty only covers the region north of the Tropical of Cancer (Art.6), so Article 5 couldn't be invoked back then.

Little "fun fact": Japan's attack on Pearl Harbor would not be covered be the treaty, since Hawaii is also excluded by Article 6.


Invoking article 5 is a major step. Given that the main conflict during most of the 20th C and which would take roughly half of the 73 years is the cold war between the USSR and the USA, strenuous attempts would have been made by diplomats to not invoke article 5 to avoid being drawn into a wider conflict. NATO is, after all, a defensive alliance.

Notably, no terrorist attacks on member countries - apart from 9-11 - led to article 5 being invoked. It would have been like using a sledgehammer to crack a nut.

It's only the scale of the tragedy of 9-11 that led to article 5 being invoked. In my personal view, this was a mistake, although probably understandable in the early aftermath. In fact, as a high German official stated, the USA was considering using nuclear weapons as "all options were on the table."

Europe itself, the theatre for two European wars in the early to mid 20C, simply wasn't interested in war any longer. It wanted to build peace and this led to the building of the EU as a bulwark against any future belligerant nationalistic fervour breaking out into war.

NATO had served its purpose when the old Soviet Empire collapsed, and like Jack Matlock said, the more or less last US ambassador to the USSR, a new security architecture emcompassing the West and East Europe would have been in the best long-term interests of both parties. This was not to be as we now see in the tragic sitiation in Ukraine.

  • It's difficult to say how that new security architecture could have looked like. Just because something is new it must not be better. Eastern Europe clearly saw a continuing purpose in NATO and Russia somehow didn't really want to be part of many architectures either. The war between Russia and Ukraine now can also be seen as confirmation of the ongoing value of NATO. Commented May 9, 2022 at 6:39
  • @Trilarion: Actually, Matlock said they were well into building that new security architecture when they were pushed back by the executive. This is why he testified in Congress on disbanding NATO. He also said that one of the flash-points would be the Ukraine. What's happening now is exactly as he predicted. That waa what - twenty or thirty years ago ... Commented May 9, 2022 at 6:44
  • Sure, there were ideas but estimating their value and validity will always remain speculative. Eastern Europe desperately wanted to be part of NATO. That at least says that there was a value for some in the past 20 years. If Sweden or Finland wants to join now, it might mean that still there is value in NATO. Russia with its doomed thinking of a big empire that needs to be conquered, is a threat to everyone surrounding. Not saying this is the only interpretation, but certainly it's one that would give value to NATO. Commented May 9, 2022 at 6:54
  • @Trilarion: They wanted to the cold war to be over. Right now it looks like boiling up into another one. NATO should have been history. Its useful life was over and new security architecture encompassing East & West would have worked then. Commented May 9, 2022 at 6:56
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    "The USSR was defeated." Not really. Not in the sense that Germany was. "except in the former Yugoslavia. Yugoslavia wasn't part of the USSR. "West Germany was made a part of a new Europe" After an occupation that installed a Western-style government. Russia, on the other hand, was taken over by the KGB with a new face. "as the two nuclear super-powers could have abandoned their nuclear armory." What about China? "It's a moment that future historians will wonder what possessed the USA to carry on pushing onto Russia." What does that mean? And Russia approved much of the expansion. Commented May 9, 2022 at 7:48

NATO has taken collective defense measures several times at Turkey's request. For example, it was the deployment of the Patriot air defense system during the Gulf War in 1991, a set of defensive measures and the conduct of Operation Display Deterrence during the crisis in Iraq in 2003 and the deployment of the Patriot air defense system in response to the situation in Syria in 2012. However, this was not considered an application of the fifth article.

  • Did they invoke article 5 though?
    – Joe W
    Commented Jun 26, 2023 at 20:03
  • @Joe W No, but there seems to be examples where it was close to be invoked.
    – convert
    Commented Jun 26, 2023 at 20:13
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    @convert was Turkey attacked during the Gulf War? If not then there were no grounds for invoking article 5.
    – phoog
    Commented Jun 26, 2023 at 23:15

The wording of the question is so ambiguous that it in fact asks 2 different questions.

has there really been only one occasion where NATO's article 5 applies?

Could mean either

  • "has there been other occasions when article 5 was invoked?", or
  • "has there been other occasions when the circumstances allowed for article 5 to be invoked even though the attacked country elected not to invoke it?"

The answer to the 1st question is "no, not so far" according to "Foreign Policy Research Institute."

And while there have been many times when military assistance was supplied to buttress allies' defenses, no other formal invocation has ever taken place.

The answer to the 2nd question is definitely a "Yes."

For example, the USSR shooting down of the US spy plane over Cuba could have lead to article 5 invocation because, in a private conversation, the US referred to it as "drawing the 1st blood":

Ellsberg said that Robert Kennedy (RFK) told him in 1964 that after the U-2 was shot down and the pilot killed, he (RFK) told Soviet ambassador Dobrynin, "You have drawn first blood ... . [T]he president had decided against advice ... not to respond militarily to that attack, but he [Dobrynin] should know that if another plane was shot at, ... we would take out all the SAMs and antiaircraft ... . And that would almost surely be followed by an invasion."

So it was deemed to be an act of war.

A question was raised in comments of whether Cuba would qualify under article 6.

The legal analysis in the this article states that the question of a limited area of the action of the treaty was considered.

And while the area of effect was specified by the article 6 to end at the Tropic of Cancer (a latitudinal line which passes just North of Havana), it was not meant to be a hard limit or a boundary, but rather a description of the general area where the treaty would be in effect.

the word area is to be understood to cover the general region rather than merely the North Atlantic Ocean in a narrow sense. This is also confirmed in the 1949 Executive Report on the North Atlantic Treaty produced by the U.S. Senate Committee on Foreign Relations. In it, the U.S. Senate stressed that “[i]n view of the purpose of the treaty to deter armed attack, the area covered by the treaty was deliberately described in general terms rather than defined by the lines of a map.

Lastly, since the retaliation described by RFK would have clearly been a massive military action, it would have been to the benefit of the European NATO allies to be prepared for a European escalation by the USSR. So invocation of the article 5 would have been in line with the gravity of what would be about to happen.


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