The fall of the Berlin Wall seemed to herald the end of the Cold War and the emergence of a single superpower. A resurgent Russia's actions in Georgia have shattered that illusion

When Gordon Brown sits down tomorrow at the conference table with the 26 other EU premiers in the glass-fronted Justus Lipsius building on Brussels's Rue de la Loi, the significance will not be lost on any of those present. The last time they sat in emergency session was in 2001, immediately after al-Qaeda's attack on America.

This time, they will be meeting to consider Russia's military actions in response to Georgia's attempt to retake South Ossetia. Those present are likely to agree with British Foreign Secretary David Miliband who declared last week that a new era in international relations was upon us: the post-post Cold War, as former US Secretary of State Colin Powell originally framed it. Russia's intention to absorb both South Ossetia and Abkhazia into the Russian Federation is being treated as a move of that magnitude.

History, to reverse Francis Fukuyama's pronouncement on its ending, has decisively begun again. The 'new world order' envisaged in the aftermath of the fall of the Berlin Wall, an order in which liberal democracies would proliferate across the world as the United States exercised a benign global hegemony, has proved to be a mirage. First 11 September and then the debacle of Iraq shattered that happy illusion nurtured in the thinktanks of Washington.

Now, in the space of a few weeks, Putin's tanks have buried it once and for all. In the face of protests, exhortations and furious remonstrations, Moscow acted as it saw fit in what it considers the Russian backyard, and damned the consequences, assuming there would be none of any note. This is no unipolar world, designed to Western specifications.

In Syria, Libya, even Turkey (a US and European friend) politicians and analysts have noted the consequences of the Georgian crisis - not for what Russia has done but for what the US, EU and Nato have been unable to do: exercise their power to protect an ally.

Trading of accusations has accelerated, with Russia's Prime Minister Vladimir Putin charging - in language that would not seemed out of place coming from the lips of dour Soviet Cold War-era Minister for Foreign Affairs, Andrei Gromyko - that the US had armed Georgia for war, and suggesting that US military advisers may have been present during fighting.

'I do think this is a pivotal moment,' says Stephen Flanagan of the Center for Strategic and International Studies in Washington, 'not least with Russia's rapid recognition of Abkhazia and South Ossetia. It puts into question one of the fundamental assumptions of the post-Cold War era - you don't change borders. Or at least you don't if you're one of the key stakeholders.'

Flanagan's assessment is echoed by a senior European diplomat working on the Georgia crisis, who says: 'The widely held view among people who think about these things in Europe as well as Washington, was that Russia was determined to respect borders at the ending of the Soviet Union. That is the major change.'

But if there is agreement that one era of diplomacy has passed, there is less agreement over the nature of the new period and how to negotiate its uncertainies.

For Ivan Krastev of the Centre for Liberal Strategies - and Republican presidential nominee John McCain's foreign policy adviser, Robert Kagan - the Georgian crisis echoes the power plays of a century ago. 'Europe,' he wrote soon after the fighting, 'has entered a new 19th century, vapourising the end-of-history sentiment that shaped European politics in the 1990s and replacing it with an older, geopolitical calculus in a modern form.'

On the surface, at least, the return to gun-boat diplomacy appears confirmed by the spectacle of the warships of five nations cluttering the Black Sea, and US and Russian troops competing over two of Georgia's ports. But if a new Cold War is coming it is clear it will not be much like the old - or even the brief outbreak of conflict in Georgia. With a high oil price, £300bn in its reserves, European dependency on Russian energy, and wider dependency on Russian co-operation in issues like Iran and the Middle East, Russia is already well-armed with the weapons needed to fight this war.

While many analysts have taken the Kagan/Krastev line, others are sceptical of describing the new era solely in terms of a competition between the democracies and the autocracies. Clifford Gaddy of the Brookings Institution, who has met both Putin and George Bush on several occasions, believes that Georgia is a 'turning point' but is more cautious about apportioning the blame entirely on Putin and his vision of Russia.

'The Georgia crisis is not unique in itself. It has simply been the event that wakes people up to what has been already happening. I really think that many leaders in the West failed to acknowledge what was happening. I liken it to a financial bubble, and the implicit assumption was that Russia was weak. We considered multiple models for Russia, except for the outcome where Russia became strong and "bad" as defined in our terms of 'good' - which means "like us". No one considered this outcome because no one imagined oil at over $100 a barrel.'

Gaddy also rejects the idea that Russia is trying to re-establish an empire or bring back a Cold War similar in scope to the last. Instead, he sees the current crisis as the inevitable reaction to the experience of Putin and those closest to him over the question of Russia's 'security' during the 1990s - when Russia veered towards becoming a failed state.

That concern, existential in Russian society, Gaddy believes was too easily discounted by the West as a rhetorical device of domestic politics: 'Russia in the 1990s was close to being a non-entity. Survival as a grand power was an issue.'

Into this was interposed the issue of Nato expansion up to Russia's very borders, sold first by President Bill Clinton and then George Bush, as a mechanism for 'democratisation' that would guarantee security. Gaddy says: 'That push was counter-productive and largely responsible for what is happening today. If we push harder, [as Gordon Brown suggests] it will confirm Russia's worst fear over what Nato is about. That is what I am afraid of - by pushing ever-harder we end up in a dangerous place.'

The feeling that the world stands in the midst of a definitive reorganisation is shared in Russia. 'We are on the verge of a new Cold War,' argues Sergei Karaganov, a former adviser to Russian President Boris Yeltsin and now deputy director of the European Studies Institute in Moscow. 'It seems like a Cold War. I can only hope it will not be so deep.'

For Karaganov, the conflict between Russia and the West has been an inevitable consequence of a scenario that many American writers have recently turned their attention to - the relative decline in US power and the unipolar world that dominated throughout the 1990s - and the emergence of a multipolar world that US and British foreign policy has been slow to react to and acknowledge.

It is not just that the West and the EU has been losing infuence because of mistakes made in places like Iraq, says Karaganov. 'Russia has contributed to what is happening, too, by being too cocky in trying to restore its position in the world too quickly. Not so long ago we were almost a failed state. Now we are one of the world's three big powers again.'

There will be much noise generated by tomorrow's meeting in Brussels, the likely outcome is an agreement on a series of minor punishments - not enough to reverse what has happened in Georgia, but enough, it is hoped, to discourage Russia in the future.

Among them, it is expected, will be a review of joint Russian-EU partnership agreements; a declaration of support for Georgia's territorial integrity (if not necessarily its President Mikheil Saakashvili, who launched the attack that led to Russia's intervention); and consideration of new visa restrictions for Russians wanting to come into the Schengen Area.

What none will be able to ignore, in a grouping that gets almost a quarter of its energy from Russia, is that the EU - like the US - has few weapons in its armoury to punish Russia, except by attempting to shame it at a time when Moscow appears determined not to be embarrassed, its President, Dmitry Medvedev, declaring the country is not afraid of a 'new Cold War'.

There are a few unwilling to be drawn into comparisons with the last Cold War. Zbigniew Brzezinski, former National Security Adviser to President Jimmy Carter, now a lecturer in US foreign policy, believes the solution to the crisis lies in old-fashioned capitalist economics, an influence notably absent in the days of the Soviet Union.

'It is serious, but it is neither fatal nor tragic. It is serious because Russia is going through a post-imperial crisis of leadership inspired by post-imperial nostalgia. It is not tragic or fatal, because Russia is not the Soviet Union. It is vulnerable, as the flight of capital from its stock market has already shown.

'The difference between Stalin and Putin is that Stalin commited great crimes on a great scale. Putin has committed petty crimes on a petty scale. And what is certain is that Russia's new business elite is not going to be happy if they think their bank accounts could be frozen or their children cannot study in the West. What is required is calm, deliberate ostracism.'