For many years now Catalonia has been attempting to peacefully secede from Spain through a binding referendum. However the Spanish authorities are constantly undermining their efforts by not accepting the results of the vote or by arresting members of the Catalan government for violating the court's order against the referendum.

But what if Catalonia were to attempt to leave through the use of force? Since it would mean that Spain is under attack, would it be possible for it to trigger Article 5 in order to call in assistance from other member states?

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    Very related: Is NATO obliged to invoke Article 5 if one of its members attacks another member? (almost duplicate, since the answer would apply here as well).
    – user11249
    Commented Sep 24, 2017 at 0:08
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    @Voo For many years... for starters. Unlike in the Basque country, the question has not been an issue in mainstream Catalan politics up to recently.
    – Miguel
    Commented Sep 24, 2017 at 4:53
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    @Miguel A pro independence party was part of government after 2003, there's been the whole second statute of autonomy in 2006 which was rather prominent even in international news. Not really new the whole discussion.
    – Voo
    Commented Sep 24, 2017 at 9:23
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    @Voo Such pro independence party neither "attempted to secede" nor organized a referendum. The statute of autonomy sort of reinforces my point.
    – Miguel
    Commented Sep 24, 2017 at 9:52
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    @Voo, the first attempt to peacefully secede from Spain through a binding referendum began this year. The "process" of 2014 was not a referendum, much less binding, even in its original form (before being watered down), as is made explicit in the name "Decret de convocatòria de la consulta popular no referendària sobre el futur polític de Catalunya". Commented Sep 24, 2017 at 17:24

2 Answers 2


No, internal conflicts and secession attempts do not qualify as “armed attacks” under the North Atlantic Treaty (itself based on the UN charter, article 51, which only covers actions between states). The most obvious historical example is the Algerian War, in which Algeria – then a part of France and covered by the treaty, as explicitly acknowledged in article 6 – fought for its independence, without the involvement of the other NATO members.

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    To be fair, France didn't want involvement since they saw it as an 'internal matter', nor were others likely to be involved, since they lacked the political will to get tangled up in that mess. Commented Sep 23, 2017 at 10:57
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    The moment Catalonia becomes it's own state, this doesn't really matter any more, does it? Or does the UN have to acknowledge Catalonia as state before it's no longer an internal matter?
    – Mast
    Commented Sep 23, 2017 at 15:13
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    @Mast: As long as Spain doesn’t acknowledge a secession, it’s an internal matter for them. And that’s what matters, because Spain (as a party to the treaty) would need to “call for help”.
    – chirlu
    Commented Sep 23, 2017 at 15:18
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    @chirlu Ah, of-course. Thanks for clearing that up.
    – Mast
    Commented Sep 23, 2017 at 15:54
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    @chirfu Article 5 doesn't require the country being attacked to "call for help" as the attack is considered to be made against all the members, and all members are obligated to assist "forthwith".
    – Ross Ridge
    Commented Sep 23, 2017 at 17:38

The treaty is geared towards international threats, so that would be unlikely.

It could theoretically trigger article 4 of the treaty. The latter states that:

The Parties will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the Parties is threatened.

It got used only a few times in history: three times by Turkey (in 2003 on the outbreak of the Iraq war; in June 2012 after the shooting down of a Turkish military jet; and in October 2012 after Syrian attacks on Turkey), then by Poland on the basis of the events in Ukraine, and again by Turkey in 2015 owing to its civil war against IS and PKK rebels.

If the reaction Turkey got in the past two decades is anything to go by, NATO would react similarly to the UN in a similar context: the treaty is about international conflicts first and foremost, in spirit if not explicitly in writing, and states are left to themselves to deal with their internal conflicts.

If things get really out of hands for Spain then article 4 could theoretically result in NATO help. But there's not a shred of sensible evidence that events in Catalonia could blow out of proportion and devolve into violent separatism. Mass protests with occasional violent clashes are a more likely outcome IMO i.e. nothing that anti-riot police can't deal with until a peaceful outcome is negotiated.

It's also worth noting in passing that begging for NATO help to deal with a bunch of poorly equipped rebels is a clearcut case of international humiliation. The UK never sought NATO help when it was dealing with its Irish problems. It would have been the world's laughing stock had it done so. Likewise, as raised by chirlu, for France and its Algerian problems.

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