How many times has Article 5 been invoked?

Article 5 of the North Atlantic Treaty has been invoked only once in history.

The Sole Invocation of Article 5

The unprecedented invocation of Article 5 occurred following the devastating September 11 attacks on the United States in 2001. This collective defense clause, a cornerstone of the North Atlantic Treaty Organization (NATO), signifies that an armed attack against one member state is considered an attack against all.

• Event Leading to Invocation: The terrorist attacks on the World Trade Center in New York City and The Pentagon in Arlington, Virginia, on September 11, 2001.
• Date of Invocation Confirmation: On October 4, 2001, NATO officially confirmed that the attacks met the criteria for an Article 5 invocation under the terms of the North Atlantic Treaty.

This event marked the only time in NATO's existence that this critical defense mechanism has been activated, underscoring the gravity and global impact of the 9/11 attacks.

Understanding Article 5

Article 5 is a core tenet of the NATO alliance, embodying the principle of collective defense. It states that if an armed attack occurs against one of the NATO member states, it shall be considered an attack against all members, and consequently, all other members shall take such action as they deem necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area. This principle is fundamental to NATO's deterrent posture and its commitment to mutual defense.

For more details on the treaty, you can refer to the North Atlantic Treaty on Wikipedia.

Historical Context of Article 5 Invocation

The invocation of Article 5 after 9/11 led to a range of support actions from NATO allies, including:

• Operation Eagle Assist: NATO AWACS (Airborne Warning and Control System) aircraft provided enhanced air surveillance over the United States from October 2001 to May 2002.
• Operation Active Endeavour: A naval operation in the Mediterranean Sea aimed at detecting and deterring terrorist activity, which began in October 2001.

This table summarizes the single instance of Article 5 invocation: