Ever since the cold war ended it has been tempting to regard Nato as an old alliance in search of a new role and a new enemy. Amid all the motorcades, flashbulbs and ceremonials of the Nato summit which concluded in Lisbon on Saturday - the most important Nato gathering for a decade, or since the fall of the Berlin Wall, depending on who you listen to - this remains the unresolved question haunting the much-expanded Atlantic alliance. That is not to say that the 28 Nato member states and their many partners, contacts and clients who gathered in Lisbon had nothing more concrete to discuss than the alliances latest strategic concept - a crisp, concise and concrete document, that was unveiled by Nato secretary-general Anders Fogh Rasmussen. On the contrary, what brought Barack Obama and many other heads of government to Portugal is one extremely urgent practical question, Afghanistan, and a clutch of other tangled regional and strategic issues that are only slightly less pressing and intractable. Afghanistan undoubtedly dominated the summit. But there were no dramatic initiatives. The reality of Nato deployment there is that, America and Britain excepted, most of the member states are doing the absolute minimum to support the mission consistent with preserving the alliance. With the Dutch gone and the Canadians going, the Obama administrations goal in Lisbon was the modest one of keeping the alliance lined up behind the four-year US handover timeline. Its simply about holding it all together. There were other big topics on the table. Two stand out - and are related. Russia is the first, though relations with the old enemy are easier now than during the war in Georgia and since the Obama administration reset the dial with Moscow. The one-time superpowers are working together on nuclear weapons reduction and Afghanistan. The other big subject was Iran, whose conduct plays to Natos need to find a new threat - not without reason in this case - against which it can justify its existence. Irans intention of producing missiles that would threaten Europe is now treated as a given by Nato strategists, and Iran has duly overtaken North Korea and Saddam-era Iraq as the justification of choice for the deployment of a US missile defence shield in Europe. But the shield is on course to become a reality now, and Russian cooperation with it has been a pivotal shift. Yet Natos underlying existential uncertainty should not be brushed aside just because there are practical matters of this kind. The fact remains that Nato was formed to defend western Europe against the Soviet Union. Over these years, Nato has attempted to reinvent itself in many ways: first as the guarantor of the newly independent former Soviet satellites and republics; then as the enforcer - eventually - of new nation states in the Balkans; and finally, since 2001, as a go-anywhere military alliance, classically in Afghanistan. Yet Natos deployment in each of these roles took place at least as much for political as for military reasons. The truth is that Nato is now more obviously something that to some extent it has always been - an international auxiliary military force of the United States. No common interests The great achievement of Nato is that it has helped to keep the peace in Europe - with occasional exceptions - for more than 60 years. And yet, 65 years since the guns fell silent, what were once common interests have naturally diverged and developed in different ways. It is no longer true that the European nations and the US have common foreign and security interests, as they once did. America no longer looks at the world through a European prism. All this has been sharply accentuated by the financial crisis, which has seen European nations slash their defence spending, to Washingtons and the militarys alarm. The upshot is that Nato today is more than ever an alliance between, on the one hand, a superpower which spends a lot on defence and is increasingly focused on the emergence of new powers in Asia; and, on the other, a lot of small nations which all spend relatively little on defence. Those small nations could certainly co-ordinate their spending more smartly and with less duplication, as Britain and France have recently pledged to do. Rasmussens proposed streamlining of Natos command structure is also manifestly overdue. But it is hardly surprising that the one remaining big spender calls most of the shots. There are better alternatives. More honourable ones too. The European members of Nato could all spend more as well as more smartly, perhaps making the 2 per cent of national income on defence target a common goal, like the 0.7 per cent pledge on aid. That way, Europe could increase its role in Nato or focus its defence policy in new and more independently European ways. Rasmussens new strategic concept document will set out all the reasons - cyber, terrorist, ballistic and nuclear - as to why the defence and security job has to be done, in our name and whether we like it or not. If we dont own it, pay for it and do it ourselves in our way, it will be done by the Americans in theirs. And in two years time, if recent reports are to be believed, that might even mean by Sarah Palin. Martin Kettle is an associate editor of the Guardian Gulf News