The North Atlantic Treaty Organization, in terms of conventional military capability, is by far the best resourced and most sophisticated regional or multilateral organization in the world. Its 26 countries - which will become 28 following the Strasbourg-Kehl NATO summit later this week - together have a formidable war-fighting and peace enforcement capacity, in terms not only of the raw numbers of both personnel (some 2.5 million in uniform) and equipment (over 5,000 helicopters for a start) but also their interoperability, highly professional and integrated military command structure, and ability draw on the contributions of non-EU countries like Turkey and Norway.

Moreover, while never having had to fire a shot during the Cold War, it has demonstrated in more recent years considerable competence in the actual conduct of military operations, whether those missions have been highly controversial, as with Operation Allied Force in Kosovo from March to June 1999 (because of the absence of Security Council authority), or much more accepted, as in the cases of the Implementation Force (IFOR) and Stabilization Force (SFOR) in Bosnia from 1995 to 2004 (NATO'S first ever out-of-area deployments), the Kosovo Force (KFOR) from June 1999, and the International Security Assistance Force (ISAF) in Afghanistan since 2001.

It is true that some significant institutional problems have become apparent in the course of these operations, particularly in Afghanistan, and remain to be resolved: notably serious differences in the willingness of its member states to contribute troops and resources, to make them available for hard-end fighting tasks when they are contributed, and to agree on common rules of engagement when they are so deployed. But any way one looks at it, NATO is a formidable fighting force. And it's one that has shown at least some signs of being willing to spread its wings beyond its traditional roles of defending its members from attack, from within or without, and in a way that is basically confined to the Euro-Atlantic area.

In 1999 NATO updated its Strategic Concept to provide for members of the alliance to defend not just other members but to conduct a full range of "non-Article 5 Crisis Response Operations" to ensure peace and stability in its region and periphery; then at its Prague conference in 2002, it agreed even more specifically that its forces could be sent "wherever they are needed," abandoning the restriction of acting in defense of the treaty area alone. This has been followed by some significant reorganization of NATO's military structure to meet evolving demands of this kind, with there being at least notionally fully operational since 2006 a NATO Response Force (NRF) of 25,000 troops--with land, air, and sea components that train together and become available for six months before being replaced. Its role is to act as a stand-alone military force available for rapid deployment as a collective defense, crisis management, or stabilization force, although so far NRF members have performed only relatively minor and uncontroversial tasks, like providing humanitarian relief after Hurricane Katrina and the Pakistan earthquake in 2005.

The question arises as to what all this capacity is for, and whether it can or should be used for a wider range of global peace and security tasks. And in particular the question arises as to what role NATO can and should play in helping implement the international responsibility to protect vulnerable populations against mass atrocity crimes - genocide, ethnic cleansing, other crimes against humanity and war crimes committed in internal conflicts. As most of this audience will know, the responsibility to protect norm was adopted unanimously by the UN General Assembly in 2005 by over 150 heads of state and government meeting as a World Summit on the UN's 60th anniversary, against a background of long failure to reach any kind of consensus on how to react to these atrocities, which dates back centuries but came to a head in the series of catastrophes in Rwanda and the Balkans through the 1990s.

The core elements of the new responsibility to protect norm can be very simply stated. First, sovereign states have the responsibility to protect their own people against mass atrocity crimes. Second, where they need assistance in doing do, others have a responsibility to help them (including where necessary by providing, at the request of the government in question, military forces for human protection purposes). And third, where they are manifestly failing to protect their people - perhaps because of ill-will rather than incapacity - then the wider international community has the responsibility to take appropriate collective action, in a timely and decisive manner (including in extreme cases, if the Security Council agrees, the use of coercive military force). The responsibility to protect - unlike the doctrine of the right of humanitarian intervention, which it was expressly designed to supersede - of course involves much more than just the use of military force, but it is that small part of the total picture which is relevant to the present discussion about NATO's role.

As efforts have continued since 2005 to consolidate and effectively implement the new norm, one of the many issues that arises is where - in those cases that need it - is the relevant military capacity to come from, not only in peacekeeping operations accepted more or less voluntarily by the governments concerned (which may have a significant ongoing peace enforcement dimension, as for example is the case with the UN's MONUC operation in the Congo, or the combined UN-AU UNAMID operation in Darfur), but more particularly, for present purposes, in straight-out fire-brigade type coercive peace enforcement operations (of the kind mounted briefly by the EU's Operation Artemis in the Congo in 2003 , or - going back further - the UK in Sierra Leone in 1997 or the West African regional organization ECOWAS in Liberia in 1992, and which should have been mounted, but wasn't, in Rwanda in 1994).

Finding that sharp-end capacity has been a recurring source of immense frustration for policymakers. The idea of a standing UN volunteer army is endlessly debated but no closer to acceptance than it has ever been. Even just a UN rapid reaction force, built of national components on standby but almost immediately deployable, has proved impossible to construct. On the face of it, NATO's NRF - assuming it could be made in practice to work as well as it does on paper -- is exactly the kind of "highly mobile, self-sustaining rapid reaction force...uniquely prepared to respond to a fast moving genocide, such as occurred in Rwanda in 1994."

There are practical issues to be resolved if NATO is to play this role, in addition to some of the institutional problems already mentioned. Given the other demands on NATO members in Afghanistan, Iraq, and elsewhere, it cannot be assumed that the necessary troops, even if formally committed to the Response Force, will be readily available. Force configurations in most NATO countries are still very much those of the Cold War, and the percentage of uniformed military personnel that are actually deployable on international peace operations at any given time is very small--most informed estimates suggest the figure is only 3-4 per cent. It certainly cannot be assumed, given the requirement for consensus in any decisions of this kind by NATO's governing body, the North Atlantic Council, that agreement will be reached, quickly or at all, to send them. And it certainly cannot be assumed that any military enterprise by NATO, even if mandated or endorsed by the Security Council, will be greeted without suspicion or hostility elsewhere.

But the more fundamental problem is that NATO has still not worked out, in the post-Cold War world, what kind of organization it wants to be, and there is bound to remain a degree of both external hostility and internal division until it does. There seem to me to be three broad options among which the organization, sooner or later, has to choose.

One is for it to retreat into Cold War nostalgia and remain essentially the organization it was in the past, a transatlantic regional defense alliance concerned above all about threats from the east, willing to embrace as new members any Euro-Atlantic countries committed to democratic, market-oriented values but nervous about Russia -- incapable of even conceptualizing it as a member of the organization itself -- and prepared to deploy out-of-area only in situations, like Afghanistan after September 11, where the security interests of alliance members are seen as directly and immediately at risk.

A second option, advanced in 2007 by five retired NATO generals (Naumman, Shalikashvili, Inge, Lanxade and van den Breemen), is one certainly rooted in Cold war nostalgia but with some nuanced and sophisticated additions: there would continue to be an inner ring of transatlantic members wholly committed to existing standards of democracy, human rights, and good governance, and to mutual defense (including by nuclear first strikes if that's what it took); a second circle of partners--including Russia, and possibly China and India--with whom the inner ring could work on conflict and crisis prevention; and an outer ring of more distant partners and allies who shared inner-ring values and convictions--presumably including countries like Japan and my own Australia--with whom the inner group could promote general stability and possibly join in coalition-of-the-willing interventions and stabilization operations, not necessarily feeling constrained by the need to seek prior approval from the UN Security Council for any use of coercive force.

A third option, and one that I very much prefer, would be for NATO to quite fundamentally recast its role and become a global military resource, potentially available to prevent and resolve security problems worldwide in partnership with others as circumstances required or allowed, but deploying anywhere only with UN authority. Such a NATO would not just defend its members against attack from within or without but be prepared to contribute when asked to human protection missions, and above all to play the role of emergency force provider in response to conscience-shocking mass atrocity crimes - the responsibility to protect situations I have been describing. Gendarmes du monde--"policemen of the world"--is a phrase that already causes much concern both for nervous NATO members themselves and for others concerned by the organization's perceived liking for throwing its weight around, and this badge would no doubt be applied to any enterprise of the kind described. But there is a large difference between an organization operating within constraints set by the UN Security Council and one working freelance, and it is not inconceivable that in this context the badge could become one of honor. That said, a fundamental reshaping of NATO's role in this way is not likely to be possible any time soon and certainly will not be achieved in a single leap.

Perhaps the best starting point for rethinking the kind of contribution NATO could most usefully make to global peace and security in the twenty-first century is the "three circles" approach in the second ('five generals') option I described above, but to put aside its Cold War flavor once and for all and make it more universally attractive. This would probably involve NATO being prepared over time to relax the wholly Euro-Atlantic geographic character of the inner ring; and certainly would involve it being prepared, in a way the five generals were not, to accept the constraint of Security Council approval for any use of force not involving self-defense in response to actual or genuinely imminent attack.

But above all, it would seem to require that NATO be overtly willing to welcome Russia itself into the "inner ring", at least if it satisfies the kind of democracy and human rights conditions being demanded of other former Soviet bloc countries. With the tensions and feelings generated by Russia's invasion of Georgia still running high, not least among the Central and Eastern Europe members of NATO, it is not easy to contemplate such a membership offer being made any time soon. But the apparent failure of a general ability to even conceptualise, let alone offer, Russian membership of the organization, seems to my outsider's eyes, to have been wholly counterproductive. The problem with NATO's expansion was never that it extended to Russia's borders: it was that it stopped there. To so obviously continue to regard Russia as the beast from the east, whose aggressive resurgence would be only a matter of time, was from the outset manifestly a very self-fulfilling enterprise, and so it has proved to be.

An expanded and open-minded NATO, no longer focused on collective defence but collective security in the broadest sense, still able and willing to protect its own members from threats both without and within but also focused on a wider global role, and willing to use its resources, working with the United Nations, to advance and protect our common humanity, would be an exciting new player on the global stage, and one that over time would generate far less global suspicion and antagonism than it would global support.

Gareth Evans is the President of the International Crisis Group.