the only Article 5 operation on anti-terrorism that NATO has ever had."
https://www.nato.int/cps/en/natohq/topics_7932.htm
"Operation Eagle Assist began on 9 October 2001 following the North Atlantic Council's 4 October decision to take measures to operationalise Article 5 of the Washington Treaty."
https://www.nato.int/docu/update/2002/04-april/e0430a.htm