How many times has Article 5 been invoked since NATO's founding?

• A. Never invoked
• B. Once (after 9/11)
• C. Twice
• D. Multiple times

Answer: (B)

Article 5 is NATO’s mutual defense pledge: if one member is attacked, all members consider it an attack on themselves and can respond collectively. This clause has been invoked only once in NATO’s history, in the aftermath of the September 11, 2001 attacks. That day, the alliance activated Article 5 to show solidarity with the United States and to support efforts related to that crisis, including NATO’s role in Afghanistan. Since then, there have been many NATO operations and activities, but none have used Article 5 again. So the best answer is that Article 5 has been invoked once, after 9/11.