By Bridget Kendall
BBC diplomatic correspondent
The dramatic violence of the last few days may have come as a surprise, but the row over South Ossetia goes back years - to the break-up of the Soviet Union.
When in 1991 Georgia claimed its right to be an independent country, separatists in its enclave of South Ossetia insisted they could do the same.
This is a chance for Russia to demonstrate its military power
Russian peacekeepers were brought in to keep the lid on tensions.
But as with time Russia began to flex its muscles and talk of itself as the guarantor of security in the region, and protector of the many South Ossetians to whom it had given Russian passports, it was inevitable tensions would flare up.
Georgia sees this as a land grab. Russia claims it is protecting its civilians from aggression.
And any mediation by Western powers is going to be difficult.
Piling on pressure
What has riled Russia most of all has been Georgia's ambition to join Nato.
Moscow has repeatedly warned that this would be a move it could not accept.
But emissaries from the US and the European Union who are Nato members are hardly likely to be seen as honest brokers by the Kremlin, when it comes to Georgia.
Russian PM Vladimir Putin has taken a firm line
And an attempt by the UN Security Council to agree a statement on a truce failed for the third day running.
Western nations are now piling on the pressure.
The United States said both sides shared some blame but Russia's use of force had been disproportionate and it must join Georgia's offer of an immediate ceasefire.
Britain urged Russia to respect Georgia's territory, and France warned Russia its relations with Europe could suffer if it did not do so.
Several EU countries criticised Russia for violating Georgia's borders by sending troops in.
Russia says it is acting to protect civilians from aggression
But whether Western attempts at mediation will make much difference is uncertain.
The danger now is that Russia will not only use this crisis to demonstrate its military power in the region, but argue it is time to redraw the map.
Arriving on the border on Saturday, Vladimir Putin declared it was unlikely now that South Ossetia would reintegrate with the rest of Georgia.
This is precisely the outcome Georgia was trying to avoid.