“Force cannot be the basis for the demarcation of new lines around Russia.” The German Foreign Minister offered this precise summary of the challenge facing Nato in Georgia as he arrived for yesterday's emergency summit in Brussels. Almost simultaneously, seven Russian armoured vehicles drove west out of Gori.

A withdrawal of sorts had begun. It offered some consolation on a bleak day for Nato commanders, informed yesterday morning of the deaths of ten French troops in a clash with Taleban forces in Afghanistan. President Sarkozy promptly vowed to fly there, and affirmed that “the cause is just”.

The same can be said of Nato's task of containing Russia in the Caucasus. For all the alliance's hesitancy in recent days, this task is also achiev-able: the crisis there may have left relations between Russia and the West chillier than at any point since the Cold War, but, as yesterday's troop movements showed, Western diplomacy and Russian manoeuvring have seldom been so tightly linked.

The lesson for Nato is clear: Moscow, for all its bluster, is paying close attention to steadily mounting condemnation of its Georgian adventure. Nato force is still a last resort. Its use is all but inconceivable in Georgia. But Nato unanim- ity counts for a great deal.

Yesterday's pullback from Gori was better than intransigence, but it was limited. As the small contingent of armoured vehicles headed for South Ossetia, more Russian troops looked on from the roadside, going nowhere. Their commander said that a full withdrawal would have to wait until his forces had set up what he called “peacekeeping posts”. Despite a prisoner exchange aimed at calming tensions near Tbilisi, Russian units remained within easy striking distance of the capital. Farther west, there was no sign of a withdrawal from the strategic port of Poti, nor from Abkhazia, where 1,000 Russian troops have arrived in the past two weeks.

Such is the reality on the ground. It mocks the ceasefire agreed with President Sarkozy two days into the crisis. It may yet make Condoleezza Rice, the US Secretary of State who brokered a second deal last Friday, look equally naive. But it has hardened Nato unity.

As David Miliband, the Foreign Secretary, wrote yesterday in The Times, “Russian mind games on withdrawal do them no credit”. The US, long since the most enthusiastic champion of Georgian membership of Nato, now proposes the establishment of a permanent Nato-Georgia Commission. Germany had resisted further Nato expansion for fear of antagonising Moscow, but now explicitly supports Georgian membership.

Much of the rhetoric emanating from Moscow is for domestic consumption. Some of it, including the weekend's absurd threat of a nuclear strike on Poland if it proceeds with a missile defence pact with the US, may be symptomatic of power struggles between President Medvedev's Kremlin clique and an increasingly vocal military over which he exercises only nominal control.

This is not the time for similar bellicosity from the West. There is little to gain and much to lose by issuing further ultimatums as long as Russia continues to withdraw. But Nato warships should remain in the Black Sea until the pull-back is complete. The Organisation for Security and Co-operation in Europe must insist on replacing Russian peacekeepers in the region with its own. And the EU as well as Nato must agree and publish detailed mechanisms for isolating Russia should it persist in dragging its feet.

Mr Miliband has advocated “hard-headed engagement”. But actions must have consequences. For now, Nato needs to be more hard-headed with Russia and less engaged.