The key section of the treaty is Article 5. Its commitment clause defines the
. It commits each member state to consider an armed attack against
one member state, in Europe or North America, to be an armed attack against
them all.
It has been invoked only once in NATO history: by the United States after the
in 2001.
The invocation was confirmed on 4 October 2001, when NATO determined that the attacks were indeed eligible under the terms of the North Atlantic Treaty.
The eight official actions taken by NATO in response to the 9/11 attacks included
and
, a naval operation in the
which was designed to prevent the movement of terrorists or weapons of mass destruction, as well as enhancing the security of shipping in general. Active Endeavour began on 4 October 2001.
It is a common misconception that NATO involvement in
was a result of Article 5's invocation.
In April 2012, Turkish Prime Minister
considered invoking Article 5 of the NATO treaty to protect Turkish national security in a dispute over the
.
The alliance responded quickly and a spokesperson said the alliance was "monitoring the situation very closely and will continue to do so" and "takes it very seriously protecting its members."
On April 17, Turkey said it would raise the issue quietly in the next NATO ministerial meeting.
On April 29, the Syrian foreign ministry wrote that it had received Erdoğan's message, which he had repeated a few days before, loud and clear.
On 25 June, the Turkish Deputy Prime Minister said that he intended to raise Article 5
at a specially-convened NATO meeting
because of the downing of an "unarmed" Turkish military jet which was "13 sea miles" from Syria over "international waters" on a "solo mission to test domestic radar systems".
A Syrian Foreign Ministry spokesman insisted that the plane "flying at an altitude of 100 meters inside the Syrian airspace in a clear breach of Syrian sovereignty" and that the "jet was shot down by anti-aircraft fire," the bullets of which "only have a range of 2.5 kilometers (1.5 miles)" rather than by radar-guided missile.
On 5 August, Erdoğan stated, "The
[in Syria] and the land surrounding it is our territory. We cannot ignore any unfavorable act against that monument, as it would be an attack on our territory, as well as an attack on NATO land... Everyone knows his duty, and will continue to do what is necessary."
NATO Secretary-General
later said in advance of the October 2012 ministerial meeting that the alliance was prepared to defend Turkey, and acknowledged that this border dispute concerned the alliance, but underlined the alliance's hesitancy over a possible intervention: "A military intervention can have unpredicted repercussions. Let me be very clear. We have no intention to interfere militarily [at present with Syria]."
On 27 March 2014, recordings were released on YouTube
of a conversation purportedly involving then Turkish foreign minister
, Foreign Ministry Undersecretary
, then
(MİT) head
, and Deputy Chief of General Staff General Yaşar Güler. The recording has been reported as being probably recorded at Davutoğlu's office at the Foreign Ministry on 13 March.
Transcripts of the conversation reveal that as well as exploring the options for Turkish forces engaging in
operations inside Syria, the meeting involved a discussion about using the threat to the tomb as an excuse for Turkey to intervene militarily inside Syria. Davutoğlu stated that Erdoğan told him that he saw the threat to the tomb as an "opportunity".
Prior to the meeting of Defence Ministers and recently appointed Secretary-General
at Brussels in late June 2015,
it was stated by a journalist, who referenced an off-the-record interview with an official source, that "Entirely legal activities, such as running a pro-Moscow TV station, could become a broader assault on a country that would require a NATO response under Article Five of the Treaty... A final strategy is expected in October 2015."
In another report, the journalist reported that "as part of the hardened stance, the UK has committed £750,000 of its money to support a counter-propaganda unit at NATO's headquarters in Brussels."
