NEXT week's NATO summit in Lisbon is likely to be one of the most crucial in the 61-year history of the military alliance. Officially, the 28 members are meeting mostly to approve a new “strategic concept” that frames the threats NATO faces and the ways in which it should defend against them over the next decade.

It is 11 years since the last such concept was adopted. In that period, both the world and NATO itself have changed greatly. But attention will focus on more immediate worries: above all, the prospects for the long war in Afghanistan, the response to Iran's nuclear ambitions and the need to “reset” NATO's ambiguous relations with its old enemy, Russia, after the chill caused by the invasion of Georgia in 2008. All this comes at a time of tumbling European defence spending and fears that America, preoccupied by strategic competition with China and by global terrorism, sees NATO as less vital to its security than in the past.

The new strategic concept itself should be easy to agree to. It is a sensible document, the result of a report drafted by a “group of experts” led by a former American secretary of state, Madeleine Albright. Last month NATO officials were claiming that it was “98% there”, and although members continue to differ on some issues, such as the alliance's future nuclear posture (of which more later), those will be papered over in Lisbon.

At the heart of the document is a restatement of NATO's core commitment to collective defence, enshrined in Article 5 of the North Atlantic Treaty. However, it recognises that there is little likelihood of an orthodox military assault across the alliance's borders. Most of the threats NATO faces are of the unconventional kind: from terrorism, rogue states with weapons of mass destruction, disruption of global supply lines, or cyber attacks on critical infrastructure such as power grids.

It is particularly hard for the alliance to decide when threats of this kind reach a level of seriousness that warrants an Article 5 response. NATO's bullish secretary-general, Anders Fogh Rasmussen, formerly prime minister of Denmark, says there is nothing wrong with a bit of “constructive ambiguity”. Others say that NATO will know the moment when it sees it, as happened when Article 5 was invoked for the first time after the terrorist attacks of September 11th 2001. But what about a big cyber-assault? At least at first, it may be impossible to tell who the instigators are.

The alliance will want to show its determination to press ahead with a territorial shield against ballistic missiles. Mr Rasmussen thinks this should convince members' sometimes sceptical publics that NATO can protect them against new threats. In the past, ballistic-missile defence (BMD) has been bedevilled by uncertainty over the technology, arguments about where the radars and interceptors should be put and the fear in some countries (most of all in Germany) of upsetting Russia, which still insists that the ultimate aim of a BMD system in Europe is to undermine its nuclear deterrent.

The Bush administration angered the Kremlin by planning to place long-range interceptors in Poland. By contrast, Barack Obama's administration has proposed the Phased Adaptive Approach, which will deploy tried and tested theatre-of-war systems as territorial defences, starting with the sea-based Aegis and moving on to land-based SM-3 missiles a few years later.

As well as being cheaper—Mr Rasmussen reckons that the cost will not exceed $300m over ten years—the new approach is clearly designed to deal with a potential Iranian missile threat, rather than bother the Russians. Mr Rasmussen would like NATO to say explicitly that defending against an attack from Iran is “an essential military mission”. But that could cause problems for Turkey, which has been asked to be one of the first hosts for the BMD system's powerful X-band radars, but does not want to jeopardise its growing regional influence or its increasing bilateral trade and energy ties with Iran.

Rather than see BMD as an obstacle to getting on better with Russia, NATO now thinks it can become something positive. With support from the Americans, the alliance has extended a hand to Russia, suggesting it could collaborate in the system. The technical and political difficulties are formidable, but co-operation is now seen as not just a way to soothe Russian prickliness, but a means of transforming the relationship from mutual suspicion and occasional crises into genuine long-term partnership.

To Russia with love

There is some excitement that Russia's president, Dmitry Medvedev, after his meeting in Deauville last month with France's Nicolas Sarkozy and Germany's Angela Merkel, has accepted an invitation to come to Lisbon. There he will attend the first meeting of the NATO-Russia Council, which was created in 2002, since the row over Georgia.

Nobody is expecting Mr Medvedev to sign up to BMD just yet. But given the range of common interests that NATO and Russia have—from slowing the proliferation of weapons of mass destruction to preventing conflicts in the Eurasian region and fighting terrorism, maritime piracy and the illegal drugs trade—there is hope that something constructive can be forged. In particular, Russia may agree to be more helpful in Afghanistan, providing helicopters, training for the Afghan army and secure supply routes for NATO's military equipment. Although NATO will maintain its “open door” policy for new members, it will be a long time before Georgia can meet the requirements of membership, while Ukraine remains uncertain whether it even wants to join: thus removing, at least for the foreseeable future, one source of tension with Russia.

In a recent report for the International Institute for Strategic Studies, Igor Yurgens and Oksana Antonenko argue that there is also, from Russia's point of view, much to be gained from a new accommodation with NATO. It would advance the cause of domestic reform and accelerate the much-needed modernisation of Russia's armed forces by allowing more technology sharing with the West. It would also allow resources to be applied to real and emerging threats, rather than to imaginary old ones. A recent poll carried out by the Pew Research Centre found that 40% of Russians had a favourable view of NATO, compared with only 24% last year. That said, deeply embedded suspicions of NATO within Russia's military establishment, as well as the populist nationalism of Vladimir Putin, the prime minister, will make for stuttering progress.

Alternatives to nuclear?

Assuming that the BMD plan goes ahead, it may further complicate one very tricky issue for the alliance—the rumbling argument over its nuclear posture. NATO insiders say that some member countries have begun to see BMD as an alternative to nuclear deterrence, not as a complement to it.

The trouble started in Germany after the election last year, when the strongly anti-nuclear Free Democrats (FDP) drove a hard bargain before entering the coalition government led by Mrs Merkel. Emboldened by Mr Obama's Prague speech in April 2009 that talked of a world eventually free of nuclear weapons, Guido Westerwelle, the FDP's leader and Germany's foreign minister, committed his government to the unilateral removal of all nuclear weapons from German soil. Mr Westerwelle wilfully ignored the president's rider that the conditions for “global zero” were unlikely to occur in his lifetime, and that America would continue to need a “safe, secure and effective arsenal” to maintain nuclear deterrence.

The German démarche creates all sorts of problems. NATO has cut the number of tactical nuclear weapons it deploys by more than 85% since the early 1990s, and now has only about 200 aircraft-delivered gravity (ie, non-guided) bombs left in Europe, stationed with American and allied air crews in Germany, Holland, Belgium, Italy and Turkey. Although of doubtful utility, these weapons are still considered by most of the alliance—especially the new members from eastern Europe and the Baltic, alarmed by the aggressiveness of recent Russian exercises—to symbolise the umbilical coupling of America's strategic nuclear forces to the defence of Europe.

In a paper published earlier this year by the Centre for European Reform, a think-tank in London, George Robertson (a former NATO secretary-general), Franklin Miller and Kori Schake (defence policy experts who served in the Bush administration) argued that Germany was opening a Pandora's box by trying to provoke a debate on matters that had long been considered settled. They also accused Germany both of morally unacceptable free-riding (it is happy to be protected by America's nuclear umbrella, but unwilling to share any responsibility) and of forcing other allies either to follow suit or to make the difficult political case for nuclear deterrence to voters.

The authors noted that in contrast to NATO's deep reductions in its tactical nuclear arsenal, Russia, according to the Federation of American Scientists, has 5,400 tactical nuclear weapons, of which roughly 2,000 are deployed and can be dispatched in various ways. Moreover, Russia has not only resisted all NATO's efforts to start discussing the imbalance in their arsenals, but has recently elevated the importance of nuclear weapons in its military doctrine as a response to the weakness of its conventional forces.

Pondering: Rasmussen and Clinton

The row over nuclear issues will be put off, however, to another day. The five principles drawn up by Hillary Clinton, America's secretary of state, at a meeting of NATO foreign ministers in Tallinn earlier this year appear to have been accepted for now. These are that NATO remains a nuclear alliance; as a nuclear alliance, member states share risks and responsibilities; NATO should reduce the role and number of nuclear weapons; the allies should pursue territorial missile defence; and NATO should draw up plans for future arms-control talks with the Russians. The nuclear issue, however, will not go away. The Luftwaffe's Tornado strike aircraft, which can carry either a conventional or a nuclear payload, are due to retire from service by 2015, and Germany appears to have no intention of equipping the Typhoons that will replace them with the avionics that would give them the same dual capability.

Hard pounding

Once the new strategic concept is adopted, the summit will turn to the alliance's most pressing problem—the uncertain prospects of the campaign in Afghanistan and the lessons so far drawn from it. Although America is undertaking its own progress review next month, it is unlikely to draw very different conclusions from those the summit reaches in Lisbon. The emphasis will be on the regained military momentum of the International Security Assistance Force (ISAF), as the American troop surge begins to have an impact on the ground. There will also be an upbeat account of the timetable for handing responsibility to Afghan forces, as an increased supply of trainers supposedly builds up their capabilities and numbers.

Among the lessons learned will be the need for NATO to develop what it calls “the comprehensive approach” to crisis management—bringing together military and civil resources by working more closely with partner countries (more than 20 are contributing troops to ISAF), other international bodies (such as the United Nations and the European Union), NGOs and local authorities. In particular, there is now a feeling that as the ferocity of the insurgency in Afghanistan grew, NATO did not provide the security necessary for civilians with experience in economic development, governance, judicial institutions and police training to go on doing their work.

To many in NATO, Afghanistan is a crucible for the alliance. This year the NATO-led coalition has suffered over 600 deaths, the highest number since the American invasion in 2001 and part of a steadily mounting trend since 2003. Nobody talks of victory any longer, but of what General David Petraeus, the commander of ISAF, calls “Afghanistan good enough”. Views on how NATO has performed there are decidedly mixed.

On the negative side, the Americans (and those like the British, the Canadians and the Danes who have taken disproportionately heavy casualties) have been frustrated by the reluctance of some countries to put their forces in harm's way and by the maddening caveats that dictate their rules of engagement. One NATO insider observes that such problems arise not always because those allies “are chicken, but because they don't have the right equipment for war-fighting conditions”. That is no less damning a criticism, reflecting the toll on the alliance's fighting capability of inadequate or poorly conceived defence spending by too many of its members (see table). The war is also becoming increasingly Americanised, partly because of Mr Obama's surge, but also because a few NATO members, notably the Dutch and the Canadians, are bringing home their combat troops (while still, it seems, contributing trainers). According to almost every opinion poll, public support for staying in the fight is dwindling across Europe.

More positively, NATO is still in Afghanistan after nine long years, many of them characterised by America's neglect of the campaign while it was bogged down in Iraq. Even today, nearly a third of the forces in Afghanistan are non-American, most of them from Europe. Mr Rasmussen has also been more successful than expected in persuading members to meet Mr Obama's request last year for 10,000 additional troops. At every bilateral meeting he has banged the drum for more.

It remains an open question whether NATO can or should mount another such mission out of area. It is still a regional, not a global, organisation, but threats to its members can come from anywhere in the world. That said, it is hard to imagine NATO wanting to tackle anything as tough or as complex as Afghanistan again.

NATO's record there provides ammunition for both sides of the debate about its future. Many (possibly including Robert Gates, America's defence secretary) agreed with an article by Fred Kaplan, a commentator, in Slate, an online magazine, last February suggesting that, although America had gained from having fighting allies in Afghanistan, it had been wrong to let NATO lead the mission. Dragging in member countries that would rather not be there, he wrote, served nobody's interests.

Eric Edelman, an undersecretary of defence for policy in the Bush administration, says that Afghanistan has shown the limits of what NATO can do. In “Understanding America's Contested Primacy”, a pamphlet for the Centre for Strategic and Budgetary Assessments, a Washington-based think-tank, he argues that although NATO still has value as a regional alliance, for demographic, economic and cultural reasons it will be increasingly hard pressed “to generate substantial useful military capability”. He recommends developing partnerships with countries such as India, Brazil and Australia, which may be willing and able to do more than America's traditional allies, and which are in parts of the world that reflect today's security preoccupations.

Others see it differently. America's ambassador to the alliance, Ivo Daalder, believes that there is little support within the organisation for NATO “narrowing its ambition”. He also says that there is no “either or” between America's commitment to NATO and its search for other partners round the world. Mr Daalder adds: “This administration believes in strengthening alliances and partnerships—including NATO. You don't tackle things like Iran, climate change, proliferation, BMD or cyber-threats on your own.”

In the 20 years since the end of the cold war NATO's obituary has been written many times, so far always prematurely. In a world of fewer dragons but a great many more snakes, it can look clumsy. Yet it carries on, attempting, as next week, to reinvent itself a little every decade or so. NATO has more members than ever and other countries wish to join it. Even the most critical Americans admit they would miss it if it was not there. And whatever its failings, most of NATO's members still see it as the cornerstone of their security and the irreplaceable bond that joins America to Europe. After 61 years, the alliance shows signs of wear and tear, but it endures.