Supreme Headquarters Allied Powers Europe
Allied Commander Operations
October 26, 2021

Collective Defense

“You could say that Article 5 is the strongest article (of the fourteen articles of the North Atlantic Treaty) because it’s the foundation of collective defense.”

The heart of the [1949 North Atlantic] Treaty and key to collective defence is Article 5, which declares that if any single Ally is the victim of an armed attack, every other member of the Alliance will consider it as an attack against all members.

If Article 5 is invoked it’s the Allies’ obligation and responsibility to identify the necessary actions to undertake in that situation under the given circumstances. Each member can provide any form of assistance they think is necessary to support the attacked Ally and “to restore and maintain the security of the North Atlantic area.”