What would happen if a NATO member was compelled to go to war because of a separate defense pact they were a part of?

As an example, Russia has threatened Sweden and Finland if they try to join NATO. While these 2 countries aren't part of NATO, they are part of the EU's mutual defense clause, and the EU contains NATO members. I would assume that, should Sweden be invaded, France, Germany, and other European NATO members would be obligated to respond. Would this, then, involve other NATO countries outside the EU, like the US and UK? Obviously there would be plenty of political pressure to get involved, but I'm interested in the question of what the NATO treaties require and/or encourage.

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    As much as I would like to know the answer to this question at this point I think it is hypothetical and we can't give an answer. It would also depend on what happens to the NATO members after they join the defense of EU members who are not NATO members.
    – Joe W
    Feb 25, 2022 at 21:40
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    @JoeW I don't think it's hypothetical at all. The NATO treaties specify that if, say, France is attacked, all the other NATO nations need to defend them. But what if France is attacked because they're defending Sweden, which they're obligated to do by the EU? The answer is simply in the text of the treaties. Of course, the US could choose to help or not to help for other reasons, but I'm only asking about the NATO requirements
    – divibisan
    Feb 25, 2022 at 21:47
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    @JoeW That's purely a example that has no specific relevance to the question. I'm not looking for punditry on what is likely to happen - I'm curious what the official, ratified treaties say
    – divibisan
    Feb 25, 2022 at 22:42
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    It's possible they don't mention it at all, which would be an interesting (and concerning) answer, but I think this is absolutely something that someone with knowledge of NATO treaties (or who's willing to read them) can answer objectively
    – divibisan
    Feb 25, 2022 at 23:20
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    And it doesn't trigger if that member started the attack
    – Joe W
    Feb 26, 2022 at 14:57

1 Answer 1


The NATO treaty applies to attacks on a country within the Treaty Area. The key here is Article V:

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 recognised 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.

It has the term "such action as it deems necessary," which is not an automatic mechanism. It also says "Europe or North America."

  • The Syria conflict spilled into Turkey. This did not trigger the NATO case since NATO did not see a serious threat against Turkish territory.
  • The UK fought Argentina to defend the Falklands. Not a treaty case, because the Falklands are South Atlantic islands. Also not exactly a defensive treaty with the Falklands, but it should answer your question.
  • The US and several allies went to war against Iraq to defend Kuwait. Again not a NATO case. Some NATO members helped, in a coalition of the willing rather than the NATO framework.

So NATO members can clearly go to war without the rest. It remains an interesting question how NATO would act if a NATO member goes to war and gets counterattacked on their territory for that reason.

  • Nonetheless the CIA provided some help during the Falklands war etc. standard.co.uk/news/world/… Feb 26, 2022 at 7:27
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    @Fizz how is that relevant? The voluntary participation of a NATO member in some action undertaken by another NATO member does not imply that the participation is required by the treaty (and in fact, it was not in this case).
    – phoog
    Feb 26, 2022 at 7:31
  • Nato has been involved in out-of-area activities. E.g. From 2004 to 2011, NATO conducted a relatively small but important support operation in Iraq that consisted of training, mentoring and assisting the Iraqi security forces. The NATO-led mission Resolute Support Mission (RSM) in Afghanistan was launched on 1 January 2015, following the completion of the mission of the International Security Assistance Force (ISAF). Its aim was to provide further training, advice and assistance for the Afghan security forces and institutions. Also Libya. May 17, 2022 at 14:12

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