What, therefore, were the immediate consequences of Article 5's invocation and how has NATO coped with the fundamental change in its operational responsibilities?
While the Alliance is today extremely active in Afghanistan, where it runs the International Security Assistance Force (ISAF), Washington chose to operate outside the NATO framework in ousting the Taliban and al Qaida from Afghanistan, despite the invocation of Article 5. Indeed, to make things clear, when Richard Armitage, then US Deputy Secretary of State, came to NATO Headquarters days after the 9/11 attacks, he stated bluntly: "I didn't.come here to ask for anything."
The US decision effectively to do without NATO support reflected US perceptions of the Alliance's performance during the 1999 Kosovo campaign, the then limits of NATO's anti-terrorism capabilities, and a desire to avoid future political problems. Rightly or wrongly, NATO was associated with "targeting by committee", which was not deemed to be a sufficiently efficient mode of operation. Although the United States recognised that NATO had come a long way since the Cold War, the Alliance was clearly not configured to execute counter-terrorist operations in Central Asia. Moreover, Washington did not wish to have its hands tied by the need for consensus in the North Atlantic Council in the event of future campaigns, such as the invasion of Iraq.
Some analysts have argued that the European members of NATO failed to make a more robust response to the terrorist threat because of the absence of shared threat perception among Allies - a loss of what Phillip Gordon of Washington's Brookings Institution has called the "glue" that held the transatlantic community together for so long. However, this is not necessarily so.
Despite deep political differences over the Iraq campaign, the US National Security Strategy and the EU Security Strategy are similar documents and security professionals whose job it is to assess the threat to their countries, whether in Berlin, Paris or Washington, are largely agreed that the looming menace is extremist Islamist terrorism. Moreover, following the 2005 attacks in London and Madrid, it is clear that Europe is no longer at peace.
Despite Washington's decision to go it largely alone in Afghanistan, 14 of the then 19 NATO Allies contributed forces to the campaign to oust the Taliban and al Qaida in 2001. Moreover, the invocation of Article 5 has been fundamental to the Alliance's retooling in the intervening period to equip it with the capabilities to take on operations such as ISAF. In effect, it set in train NATO's ongoing post-post-Cold War transformation. In the process, the Alliance has built new command structures, launched various capabilities initiatives, developed some terrorism-related competencies and created the NATO Response Force. It has also moved well beyond the Euro-Atlantic area with operations and missions in Iraq, Pakistan and Sudan, in addition to Afghanistan.
NATO is not and never has been a club of homogeneous states. Rather it has traditionally provided and continues to provide different things to its different members. For many and in particular the new Allies, Article 5 remains a cornerstone of the Alliance. For others, the clause retains a greater political importance. And others see the Alliance's value in practical terms in its new out-of-area missions and operations, which are not a part of the traditional menu of war-fighting skills.
Finally, there are those who believe that NATO has demonstrated that it can adapt over time to new challenges, and that in time Article 5 may come to be understood as having direct relevance not to scenarios of invasion, but to the ways Allies collectively combat the scourge of international terrorism. As a result, while EU watchers have for years spoken of the possibility of a multi-speed European Union, NATO has already created the reality of a multi-speed alliance, that is one able to serve many purposes to cater to the diverse needs of its many members.
The debate over whether NATO remains a collective-defence organisation or whether it is turning into an alliance for collective security is largely academic. The Alliance satisfies both needs and will continue to do so for some time. Moreover, as such, it possesses capabilities that no other international organisation possesses. As for Article 5's historic invocation, we may do well to agree with the assessment of former Secretary General Lord Robertson, namely that: "It is still too early to say what the decision on Article 5 will mean in practical terms for the immediate future."