12. September 11 and the Afghanistan Mission (2001-2021)
In response to the September 11, 2001, terrorist attacks, NATO invoked Article 5 of its founding treaty for the first time, affirming that an attack against one member was an attack against all (history.com). Subsequently, NATO assumed command of the International Security Assistance Force (ISAF) in Afghanistan, aiming to prevent the country from becoming a terrorist haven. The prolonged and costly conflict exposed divergent national priorities and raised questions about the alliance’s role in out-of-area operations.
