ANALYSIS: The escalation in conflict in South Ossetia may have its roots in the Balkans.

IT was "the first day of war", Russia's main state-run television channel said last night. The presenter, looking suitably gloomy, might have added that it was the beginning of an undeclared war to protect an unrecognised nation.

The Russian Federation, still one of the most potent military forces in the world, yesterday effectively invaded its neighbour Georgia to defend, it said, tens of thou- sands of its citizens in the breakaway territory of South Ossetia. The move comes amid the latest and potentially most dangerous escalation of a conflict that has simmered for nearly 20 years.

Georgians and Ossetians have been fighting, on and off, since the dying years of the old Soviet Union. Ossetia straddles the Caucasus and the border between Russia and Georgia. To the south of the mountains, Europe's highest, are some 70,000 Ossetians, nine out of 10 of them Russian citizens. For 15 years they enjoyed de-facto independence, not least thanks to support from their fellow countrymen living in Russia. Yesterday Georgia moved to end that de-facto independence; Russia moved to shore it up. The result: the first direct engagement between official Russian and Georgian forces in nearly 300 years.

Yesterday's flare-up may have its roots in another troubled region, the Balkans.

South Ossetia, nothing more than a patchwork of towns and villages in what is formally Georgia, is one of several unrecognised states.

This February another, Kosovo, was declared independent with support from Western powers. Russia, among other opponents of the move, warned Kosovan independence would have repercussions in the Caucasus and elsewhere. South Ossetia - and another break- away Georgian region, Abkhazia - began an appeal for recognition as soon as Kosovo got its.

Georgia got worried. Its President, Mikhail Saakashvili, has long argued that Russian support of separatists in Ossetia and Abkhazia is a proxy war against his administration and desire for closer ties with Nato. A truly independent South Ossetia, Mr Saakashvili believes, would quickly seek official links with Russia. That, he fears, could lead to full-scale Russian military presence 50 miles from his capital, Tbilisi.

Many Russians are also wary of Georgia, which made a bid for membership of Nato at this year's summit.

Svante Cornell, the co-director of the Stockholm-based Institute for Security and Development Policy and an expert on Georgia, said he saw three reasons for the timing of the current conflict.

"It boils down to Kosovo independence, Nato's Bucharest summit and possibly Russian internal politics and the transfer of power," Mr Cornell said, referring to the election of Russian President Dmitri Medvedev.

Ossetians and Georgians, although both Christian in a region with a large Muslim population, come from quite different ethnic groups.

The Ossetians are ancestors of the ancient Alans, a people who once lived on the Don River in what is now Russia. They feel they were bundled into Georgia in Soviet times and should not have to live under foreign rule.

Ossetians in Russia have had their own problems, including a bloody conflict with their Muslim neighbours, the Ingushetians and Chechens. Ossetians were the targets of the largely Chechen terror attack on the school in Beslan in 2004.

North and South Ossetia, however, retain astonishingly close ties. Volunteers from the north have been involved in fighting, both last night and in the past two decades.

Jonathan Eyal, the director of studies at London's Royal United Services Institute, stressed the stakes could not be higher. An all-out war between Russia and Georgia, he was reported as saying, would amount to "the worst crisis in Europe since the end of communism".

There were signals last night that soldiers from separatist Abkhazia were eager to join the fighting, but CIS peacekeepers, most Russian, on the border between Abkhazia and Georgia said they would step in to prevent it.

Russia's invasion yesterday came after what experts said appeared to be a well-planned operation to retake South Ossetia, a clear bid to humiliate Russia and boost Mr Saakashvili's grip on power. If it was, said Mr Eyal, it may have backfired.