By Steven Eke
BBC News Russian affairs analyst
As heavy clashes are reported in South Ossetia, Russia and Georgia have swapped increasingly angry accusations.
Russia says it has played peace-keeper since the end of the civil war
Georgia's President Mikhail Saakashvili has called upon his country to "mobilise" in the face of "a very blunt Russian aggression".
Russian Foreign Minister Sergei Lavrov said Moscow had reports of "ethnic cleansing" in villages.
Russian tanks have reportedly moved towards the capital of the region, which has been under heavy bombardment from Georgian forces.
South Ossetia is a territory one-and-a-half times that of Luxembourg, with an estimated population of some 70,000 people.
It is legally part of Georgia, since its self-proclaimed independence has been recognised by no other state, including Russia.
Yet its people and their separatist leaders do not want to be part of the Georgian state, in any shape or form.
They want either to attain international recognition as an independent state, or to be united with their ethnic kin living across the border in the Russian region of North Ossetia.
Russia asserts that its role since the end of the South Ossetian war in 1992 has been that of a peace-keeper.
However, it has supported the separatist regime financially and militarily, and reportedly has a considerable number of security and intelligence operatives there.
Georgia says it is merely defending itself from external enemies
Georgia also claims that Russian mercenaries are active in South Ossetia.
The "frozen" nature of the South Ossetian conflict - as well as that in the other, separatist Georgian region, Abkhazia - has allowed Russia to preserve a vital lever of influence over its southern neighbour, a country it now views as wayward, if not hostile.
There is, of course, an international peace process, but years of work have barely begun to bring Georgia and South Ossetia together. Their positions remain fundamentally irreconcilable.
There are also clear fault lines between Russia and the West in dealing with the immediate tensions.
A Russian-drafted UN Security Council statement calling on both Georgia and South Ossetia to renounce the use of force failed to secure British and US backing.
Russia has issued most South Ossetians with Russian passports, potentially justifying direct intervention (on the grounds of protecting "its own" citizens).
Recent heightened military tension had effectively given Russia a more solid pretext for intervention.
Military involvement may risk serious losses and international condemnation but the alternative of unilaterally recognising South Ossetian and Abkhaz independence could risk an even wider conflict.
Speaking on national Georgian television, Mr Saakashvili portrayed his actions as those of the leader of a democratic, freedom-loving nation defending itself from external enemies.
While he has many influential supporters in the West, there are also those who doubt his personal democratic credentials. Or suspect he may now be strongly overplaying his hand in a military adventure in South Ossetia.
Certainly, Russia wants to stop Mikhael Saakashvili. It views him as an emotional and dangerous leader, destabilising an already restless region on Russia's southern flank.
SOUTH OSSETIA TIMELINE
1991-92 S Ossetia fights war to break away from newly independent Georgia; Russia enforces truce
2004 Mikhail Saakashvili elected Georgian president, promising to recover lost territories
2006 S Ossetians vote for independence in unofficial referendum
April 2008 Russia steps up ties with Abkhazia and South Ossetia
July 2008 Russia admits flying jets over S Ossetia; Russia and Georgia accuse each other of military build-up
7 August 2008 After escalating Georgian-Ossetian clashes, sides agree to ceasefire
8 August 2008 Heavy fighting erupts overnight, Georgian forces close on Tskhinvali
Moreover, Moscow wants an end to Georgia's crawl towards Nato membership. Just recently, the Russian Foreign Minister Sergei Lavrov, in an extended essay on Russia's position in the world, insisted that Nato should be superseded as the pre-eminent guarantor of European security.
In this vein of anti-Western, anti-Nato suspicion, another school of thought in Russia believes that Mikhael Saakashvili is actually trying to drag Nato into intervention in his country's disputes with Moscow.
Mr Saakashvili has already tried to trumpet Nato membership as a fact - not a long-term prospect. So, for the time-being, it seems inconceivable that Nato would become involved in such a way.
The "Kosovo factor" also matters.
Even before the Serbian province unilaterally declared independence, there was a strong body of thought in the Russian political and diplomatic worlds, that believed Russian recognition of South Ossetian and Abkhaz independence would be morally and politically justified.
This has become much stronger since many Western countries ignored furious Russian objections and recognised Kosovo's independence.