NATO Article 5 — Plain-English Explainer
A quick guide to what it says, how it’s used, and what would change if it were invoked.
What Article 5 says
Article 5 of the North Atlantic Treaty states that an armed attack against one or more Allies
in Europe or North America shall be considered an attack against all of them. Each Ally will take
such action as it deems necessary, including the use of armed force, to restore and maintain security.
How it’s triggered
- Evidence & attribution: an armed attack is established and attributed.
- Political decision: Allies consult and decide collectively to treat it as an Article 5
case.
- Response: each Ally determines the measures it will take, from military to non-military
support.
Has it been used before?
Yes — once, after the September 11, 2001 attacks on the United States. It led to a range of
collective defence measures, including the deployment of NATO AWACS aircraft to help patrol U.S. airspace.
Myths vs reality
- Myth: Article 5 forces every Ally to send troops immediately.
Reality: each Ally chooses what actions to take; responses can be military or non-military.
- Myth: Any border incident triggers Article 5 automatically.
Reality: incidents are assessed; only an armed attack with political consensus can
lead to Article 5.
Where to read more