The only time NATO's Article 5 has been invoked was on September 12, 2001, in response to the September 11 terrorist attacks in the United States. This invocation was a collective defense response to the attacks by the Al Qaeda terrorist group, marking the first and only invocation in NATO history.
Additionally, NATO's Article 4, which calls for consultations when a member's security is threatened, has been invoked multiple times, most recently by Poland in September 2025 due to airspace breaches by Russian drones. However, Article 4 invocation does not automatically trigger Article 5 or military action.
