Is NATO obliged to invoke Article 5 if one of its members attacks another member?
Turkey is currently doing a lot of posturing against the EU in general and its neighbor Greece in particular. Assuming Turkey were to attack Greece, is NATO obliged to invoke Article 5 (Collective defence)? Is this something defined within the NATO rules?
Related (but different) question: If Turkey enters in war, are other NATO members obligated to assist her?
It really depends on who is declared the aggressor and that's usually decided politically, not realistically. Either way, without Greece and Turkey, there is no NATO.
@Overmind : that's not a trivial thing to decide, as officially declared wars seem to be a thing of the past. Today it's more in the style of "We did not attack you! There are some activists fighting in your country claiming to be loyal to us, but we have nothing to do with them, they did what they did out of their own free initiative.".
@vsz "Oh, and, by the way, we're annexing the land that these completely independent activists just took over in your country because they voted that they wanted us to."
Note that there's no "invocation" requirement in the North Atlantic Treaty, once one party has been attacked in Europe or North America, the other parties are obligated to respond. Strictly speaking it doesn't place any obligations on NATO itself, since its not a signatory to the treaty. The organization is just the framework the parties put in place to help organize a collective defence and, if necessary, a collective response.
@vsz, yes, that's one tactic. They can blame very easy pseudo-terrorists. That's why the high end politics actually decide who's guilty. And with the media propaganda support, it's settled.
@vsz The current aggression between Turkey and Greece is mostly them intercepting each other's military aircraft, which isn't something that can be attributed to "activists who say they're loyal to us." I suppose activists could occupy one of the various small uninhabited islands that are disputed between the two countries but it's not clear how big a deal that would be. A Russia/Ukraine-style "We're totally not involved in your civil war" situation seems very unlikely, since Greece doesn't have big enough political divisions for Turkey to exploit, or enough money to exploit Turkish divisions.
@Overmind "without Greece and Turkey, there is no NATO" . Greece and Turkey joined primarily because they were worried about their communist neighbours, and that was their primary strategic value to the alliance. NATO did just fine without Greece from 1974 to 1980, and it's not clear to me what, if any, fundamental role Greece plays today. Turkey provides air bases which are useful to US actions in the Middle East but those aren't NATO activities. I suppose Turkish control of the Bosphorus helps keep the Russian Black Sea Fleet in its box.
Look at it both historically and strategically. Historically, NATO should not exist anymore. They lack the enemy they were created to 'protect' from. Strategically, look here: http://www.globalfirepower.com/countries-listing-nato-members.asp ; remove 4 and 10, ignore 1 and 8 and you're left with what ? Btw, 7,11,14,16 and everyone 19-26 will not stay for long.
The NATO treaty is surprisingly short and readable as far as treaties go. Here's (most of) article 5:
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.
Note that it doesn't make any distinction between NATO members and external parties. So if one member attacks another, the NATO members have the same obligations.
Also note that the language doesn't exactly specify what has to happen, other than "assist the Party or Parties so attacked by taking [..] such action as it deems necessary".
So what exactly will happen? It's difficult to tell. It will depend on the exact situation, and speculating on dozens on scenarios is somewhat outside of the scope of the answer :-)
As a footnote, I'd like to point out that the chances of Turkey actually invading Greece in the near-future are virtually non-existent. Barking is not the same as biting.
In a real case, it will always be a controversed debate as who the "agressor" is. Even if a country wants to agress another it will do so with a huge propaganda machine making everyone believes it's the agressed one. So in practice, if 2 NATO members started to escalate a war, both will claim support from others based on that article.
So if Turkey _were_ to attack Greece, it, as a member of NATO, would be obligated to "_assist the Party or Parties so attacked_" and have to resist itself?
@TripeHound It could decide that the "assistance" that it "deems necessary" is to invade Greece :-) The "invasion to help the people out"-excuse goes back at least to the Roman times, when Caesar claimed he was helping the Gauls out by invading them.
I'm not sure about "short and readable" - or at least am left with many questions from the quoted portion (I suppose I should read the whole thing some day): If the German embassy to Finland is attacked, is that an attack "against one or more of them in Europe or North America"? And what if Mayotte (French territory that is even considered part of the European Union, but of course not geographical Europe) is attacked?
@HagenvonEitzen Short and readable is not the same as unambiguous or even internally consistent. Short and readable just means it's easier to notice where things are ambiguous ill defined or internally inconsistent.
@HagenvonEitzen Whether an embassy would strictly fall under the terms of the treaty could be debatable; as it could be seen as the "territory" of a country (although strictly speaking it isn't) or the employees could be seen as "forces" (but some might disagree). As for Mayotte, as far as I can tell this isn't covered in the treaty (it was probably wise to exclude colonies from the treaty in 1949, with the chief exception of French Algeria).