Brent Scowcroft Center Nonresident Senior Fellow Stanley R. Sloan writes for War on the Rocks on how the actual wording of NATO’s Article V provides a significant degree of latitude in how allied nations could respond, even if it is invoked:
Reporting on the aftermath of the Paris attacks has included a good bit of speculative (and not necessarily well-informed) commentary on whether or not NATO’s collective defense provision(Article V of the North Atlantic Treaty) would come into play. As of this writing, France has not requested that Article V be invoked in response to the attacks apparently directed and organized by the Islamic State of Iraq and the Levant (ISIL).
Some commentaries assume that when a NATO ally is attacked the other allies are required to jump to their defense. In fact, Article V is carefully worded and limited, in no small part due to demands from the U.S. Congress protecting their prerogative to declare war. The passage therefore ensures that all allies are able to make their own sovereign decisions about how to respond to an attack on another ally. According to the text, if an “armed attack occurs … each [member state] … will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area” [emphasis added].