Article 5 of the North Atlantic Treaty

Article 5 of the North Atlantic Treaty establishes NATO's principle of collective defence: an armed attack against one or more allies in Europe or North America is treated as an attack against them all. Every ally must assist the attacked party, but each determines the action it considers necessary.

Nature of the obligation

The obligation arises from the North Atlantic Treaty of 1949 and is linked expressly to the right of individual and collective self-defence recognised by Article 51 of the UN Charter.

• Each ally must assist the attacked member forthwith, acting individually and in concert with the other allies.
• Assistance may include the use of armed force, but Article 5 does not prescribe an identical or automatic military response from every ally.
• The phrase "such action as it deems necessary" allows each ally to decide the form and scale of its contribution.

Trigger and limits

Article 5 applies to an armed attack, not automatically to every political dispute, security threat or crisis involving a NATO member.

• The treaty frames the obligation around attacks against allies in Europe or North America, with the treaty further specifying its geographical application.
• Measures taken must be reported immediately to the UN Security Council.
• Such measures must end when the Security Council has taken the measures necessary to restore and maintain international peace and security.

Significance for India

Article 5 makes NATO a treaty-based military alliance rather than merely a consultative forum. For India, its operation matters because NATO's collective responses can affect regional security, relations with major powers, defence partnerships and the space available for strategic autonomy.

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