Russia's Ambassador to Nato, Dmitry Rogozin, wrote last month that “with the demise of communism, reasons for the West and Russia to be in confrontation vanished”. He would be hard put to stand by his remark when Nato meets tomorrow for an emergency summit forced on its members by Russia's invasion of Georgia, especially given its troops' continued presence there despite two ceasefire deals, its extraordinary threat to Poland last Friday, and reports that it is considering arming its Baltic fleet with nuclear warheads for the first time since the Cold War.

As it happens, Mr Rogozin was wrong. There have been myriad reasons for confrontation between the West and Russia since 1991. The implosion of a hollow ideology gave way to a series of more practical grounds for dispute, from Washington's passion for missile defence to Moscow's foot-dragging over Iranian uranium enrichment. But there has been no provocation quite so blatant as the flooding of South Ossetia and parts of Georgia with Russian tanks. Nato has so far floundered in response, but this does not make it irrelevant. The opposite is true.

Nato will be 60 next year - past retirement age for most personnel under its command. Until the Georgian war, retirement, to many, seemed an option for Nato itself. It had triumphed in the Cold War against the Warsaw Pact with scarcely a shot fired in anger. It had rained high explosive on Kosovo, ending Serbian ethnic cleansing of Muslims there. But in Afghanistan, too complex command structures and absurd restrictions on some of its members' deployments too often have made its operations ineffectual. In Europe, polls taken before the August 8 invasion of Georgia found that decreasing numbers of taxpayers thought Nato vital for security. In Brussels, Nato officials are as undecided as their EU counterparts on whether to help work towards an enhanced EU defence capability, and if so how.

August 8 provided a moment of clarity. The impunity with which Moscow ordered heavy armour into Georgia showed that the principle of collective security on which Nato is based remains the only serious guarantee of its members' borders. It showed that Russia seeks nothing less than a veto on further Nato expansion. And it showed that the price of denying Russia that veto could be high: absent the threat of mutually assured destruction, the notion that an attack on one Nato member state is an attack on all, to be resisted by all, now seems more likely to lead to conflict than at any time in the Cold War.

So anyone who thought Germany might cite recent events as vindication of its opposition to further Nato expansion at the organisation's last summit in Bucharest may have been surprised to hear Chancellor Angela Merkel yesterday assuring Georgia that it would become a member of Nato if it wished to. They need not have been.

Deferring Nato membership for Georgia and Ukraine was right, not because of Russian threats but because neither country has earned it yet. Both need to consolidate their democratic reforms. In the meantime, Nato needs to fix what is going wrong in operational terms in Afghanistan. Winning hearts and minds while fighting a fanatical counter-insurgency is tough at the best of times and hugely ambitious with a multi-lingual force drawn from 40 countries.

In Brussels tomorrow Nato must address not just the immediate crisis in the Caucasus but the need to streamline its command and control systems in conflict zones. Only then will guarantees of territorial integrity for new members serve their ultimate purpose of deterring aggression.

Mr Rogozin has called Russia's relations with Nato the basis of global security. On this he is right. But those relations will founder until Russia understands that Nato means business.