It's often been portrayed in popular culture that the US falls into a civil war, in which it's treated as a purely internal matter and no other ally may intervene. In reality this would unlikely be the case with any country that's part of an alliance, and the reasons could be numerous, but it's not clear to me if it would be purely down to which side is recognised as the more democratic, has the higher chance of winning the civil war or another factor. If a civil war started in a member state of NATO, which side would the other countries in the past come to assist?


4 Answers 4


The NATO treaty does not restrict the adversaries against whose attacks members are supposed to defend one another. Thus, if one NATO member finds itself facing armed attacks by an insurrectionist group, the other NATO members promise to render appropriate assistance in order to restore security.

While the NATO treaty clarifies that military force is an option, it is also clear that it is the country rendering aid which decides what aid it considers appropriate. So a country could offer mediators rather than soldiers, and for a messy civil war with unclear legitimacy that might be the preferred course of action.

There is no manual or scoring system for NATO members to determine who is the legitimate government of their fellow NATO members. This is supposed to be obvious, and if it is ever going to be not obvious, it's going to be a case by case decision anyway.

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    Which is part of why membership is restricted to democracies with stable governments. Commented Jun 22 at 23:18
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    @Acccumulation There is no such requirement.
    – gerrit
    Commented Jun 24 at 6:26
  • 3
    @gerrit That isn't part of the explicit requirements in the charter, but in practice the existing members have governance requirements that need to be fulfilled before they vote to allow a new member to join. Commented Jun 24 at 12:52
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    @Acccumulation Like Salazar's Portugal? Commented Jun 25 at 8:19

Schmerel, in his answer refers to historical precedent and claims that

None of those conflicts received any NATO intervention.

Officially, that might be true. But informally, neutrality was hard to come by.


History of the USS Saratoga:

In the beginning of 1975, the Saratoga took part in the Locked Gate-75, a NATO operation meant to contain the influence of the Portuguese Communist Party in Portugal after the Carnation Revolution. Along with several foreign vessels, she entered the Tagus River delta and anchored in front of the Presidential Palace of Belém.

The political context is covered in this article. It explained that in that year, Henry Kissinger had been prepared to support a counter-coup by right-wing General António de Spínola parallel to the way Pinochet found indirect support by the CIA in Chile, but was opposed by security advisor William G. Hyland and the then Ambassador to Portugal, Frank Carlucci.

The article claims that the NATO exercise played a significant role in splitting the leftist side over the question of how far the "revolutionary process" should go, and lead ultimately to Mário Soares and his Socialist Party winning public support instead of the Communist Party. But it gets some facts wrong, as the NATO operation took place on 1st – 7th February 1975, while the main confrontation between right and left wing factions culminated in the second half of the year.

Wikileaks has published some cables concerning the exercise that shead at least some light on its role.

The first cable by Ambassador Carlucci states that the exercise had been planned one year earlier, that the Potuguese Government had expressly stated it wanted it to go ahead, despite the public opposition this had received from radical left groups.

The second cable is a report of NATO ambassador Bruce on discussions with its Secretary General Joseph Luns. Despite Bruce's assurances that "the U.S. realizes there is no role for NATO at this time", Luns raised concerns that the operation could not be perceived by the Portuguese public as "anything other than a hastily organized direct attempt by NATO to interfere in Portuguese internal affairs..."

So it might be concluded that the exercise was not meant to be an intervention, but was perceived as one at least by the Portuguese Radical Left. NATO was well aware of that, but all it did to counteract the impression was to confirm the planned shore leave for the crews.


Based on historical precedent, apparently they would not get involved. NATO is a defensive pact primarily focused on external threats. Not internal conflicts.

There were several coups in Turkey, the Greek junta overtook the Greek government by force, the UK had a thirty year long civil war over Northern Ireland.

None of those conflicts received any NATO intervention.

Furthermore in a civil war, due to the absence of any invading force representing any foreign, sovereign country it could be difficult to clearly determine (1)who the aggressor is and (2)what makes this a war rather than standard criminal anti-government behavior.

NATO's own website says they got involved after 9/11 once it had been determined that the attacks came from abroad. That implies that NATO would not have come to the US's assistance after 9/11 had it been a local terrorist group who attacked it.


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    @Schmerel "... the UK had a thirty year long civil war over Northern Island." No, it didn't.
    – MikeB
    Commented Jun 24 at 7:14

If a civil war started in a member state of NATO, which side would the other countries in the past come to assist?

They will assist whatever side favor their national interests. When saying "assist" I don't necessarily mean formally engaging in hostilities, and not necessarily doing so within NATO framework - as the events in Ukraine has shown assistance may go very far, without formally declaring a state of war.

Given that the US is about two thirds of NATO, and the major economic force, one can bet that most would opt for trying to calm things down, without taking either side. Indeed, it is unlikely that any state (even Russia or China) could decisively sway a potential conflict in the US to a desired outcome. Therefore placing all bets on one side and risking the US wrath, if the preferred side loses is much worse, than watching Americans fighting among themselves till one side wins.

One the other hand, a civil war in the US would be a major conflict (making Ukraine and Gaza look like peanuts), so its continuation is sure to cause economic and political disruption elsewhere (and possibility of many local conflicts that are normally kept in check by the US pressure or military presence.) So simply standing by and watching the civil war escalate is not an option either.

Finally, let me point out that foreign powers did engage in civil war in the US - during the American war of independence (which, viewed from the other side, was a separatist civil war within a British Empire) and the American civil war. In the former case, the involvement of the autocratic French regime on the side of the republican separatists proved decisive (King Louis XVI was an absolute monarch par excellence, and had later his head cut in French Revolution.)

Prise de Yorktown is a well-known painting, depicting George Washington surrounded by French military advisors: (although the decisive role in the battle was played by the French fleet.)

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Le tableau représente l'État-major de Washington au moment de la prise de Yorktown. Les deux personnages centraux sont le général Rochambeau à gauche et le général Washington à droite. Derrière les deux hommes, on reconnait le marquis de La Fayette et à droite de Washington se trouve le marquis de Saint Simon. À gauche, sur un cheval et tournant le dos, on devine qu'il s'agit du duc de Lauzun. À droite du Général Washington, le comte de Ménonville qui commanda le siège de Yorktown.

The tableau represents Washington's major at the time of the capture of Yorktown. The two central figures are General Rochambeau on the left and General Washington on the right. Behind these two, we recognize the Marquis de La Fayette and to the right of Washington is the Marquis de Saint Simon. On the left, on a horse and turning his back, we can guess it's the duc de Lauzun. To the right of General Washington, the Comte de Ménonville who commands the siege of Yorktown.

  • It appears the translation is incomplete; it still has some French in it. Commented Jun 25 at 22:21
  • @JoelHarmon Google translate is not the same as it used to be...
    – Morisco
    Commented Jun 26 at 5:05

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