The outbreak of military hostilities between Russia and Georgia in the tiny, mountainous region of South Ossetia might seem to have come out of the blue. But the prospect of open war between the two countries has been feared for years.

South Osseita, an enclave on the border of the two countries, with a largely ethnic Russian and non-Georgian population, has been a flashpoint at least since the Soviet Union collapsed, and Georgia regained its independence at the end of 1991. It is one of three such minority regions – Adjaria and Abkhazia are the others – which are in Georgia, but not of it. Having enjoyed quasi-autonomous status in Soviet times, they challenged their inclusion in Georgia in 1992, precipitating a brief, but messy, civil war.

Georgia's "rose revolution" of 2003, when a nationalist and pro-Western wave propelled the US-educated Mikheil Saakashvili to power, reopened the issue of Georgia's territorial integrity. Fearing a new attempt by Georgia to impose rule by force, Adjaria sued for peace, but South Ossetia and Abkhazia held referendums and declared independence unilaterally. In the absence of international recognition, they looked to Russia for more than moral support, which arrived in the form of "peacekeepers". Their declared purpose was to protect the ethnic Russians – many of whom now held Russian passports – from what they feared would be enforced assimilation by Georgia.

The presence of these unrecognised independent enclaves has been a perpetual irritant to the Georgian government. But the same could be said of Georgia's brazenly pro-Western stance to Russia, which also accused Georgia of protecting separatists fighting in Chechnya. Recent months have seen an escalating war of words between Georgia and Russia, along with periodic skirmishes involving unauthorised over-flights and stray missiles.

It would be easy to interpret the conflict that erupted with bombs, tanks and warplanes yesterday as a case of big, bad Russia, resentful of Georgia's independence and growing closeness to the West, taking advantage of the world's preoccupation with the Beijing Olympics to inflict some punishment on its southern neighbour.

But the rights and wrongs are confused, not least because Russia officially recognises Georgia's statehood and its territorial integrity. Nor is there any doubt that yesterday's fighting was triggered by Georgia, whose forces crossed into South Ossetia with a view to reintegrating it into Georgia. The country's Prime Minister made this clear, saying that Tbilisi's patience had "run out".

The timing, for Georgia's purposes, was perfect. The world's attention was focused on Beijing, where the Russian Prime Minister and former president, Vladimir Putin, who is still the real power in the land, was an honoured guest, along with George Bush and other leaders. The new President, Dmitry Medvedev, was in charge in Russia, but his authority is still untested.

If Georgia had hoped for a short, sharp victory to recover what it regards as its lost territory, it may be dangerously mistaken. The very circumstances that made this a propitious moment for Georgia to act, also make it especially risky. Russia, for all its oil and gas wealth, is politically and militarily weak.

At the last count, Russia had lost more than a dozen of its "peackeepers" and at least two planes. The South Ossetian capital, Tskhinvali, was said to lie in ruins. What is more, many Russians see Georgia, with its shiny new US-trained and US-equipped armed forces, as no more than a proxy for a United States intent on securing energy routes. They are in no mood to see their country humiliated by what they see as uppity southerners.

Between them, Medvedev and Putin now have their work cut out. To spread the conflict beyond South Ossetia by, for instance, attacking Tbilisi, would risk igniting the flames of war across the Caucasus and lose Moscow any moral advantage it might have had. To retreat, however, would make South Ossetia the latest in a string of bitter losses.

Moscow has been unable to stop US plans for anti-missile installations near its borders, and it could only look on as a Western consensus railroaded an independent Kosovo into existence, against the wishes of Russia's Slav brethren in Serbia. With the ethnic Russians of Georgia now under siege, the Kremlin accepts a new defeat at its peril.