South Ossetia, about 60 miles (100 km) north of the Georgian capital, Tbilisi, broke away from Georgia in a 1991-92 war that left several thousand people dead. It has close ties with the neighbouring Russian region of North Ossetia.
The majority of the roughly 70,000 people living in South Ossetia are ethnically distinct from Georgians. They complain that they were forcibly absorbed into Georgia under Soviet rule and want self-determination.
A peacekeeping force made up of soldiers from Russia, Georgia and North Ossetia monitors a 1992 truce. Tbilisi accuses Russian peacekeepers of siding with separatists, something Moscow denies. Sporadic clashes between separatist and Georgian forces have killed dozens of people in the last few years.
The Georgian president, Mikhail Saakashvili, has proposed a peace deal that would give South Ossetia "a large degree of autonomy" within a federal state. But the separatist leader, Eduard Kokoity, says he wants full independence.
In November 2006, Georgian-controlled villages inside South Ossetia elected a rival leader, the ex-separatist Dmitry Sanakoyev. While he is endorsed by Tbilisi, his authority only extends to a small part of the region.
Russia has found itself pitted against the west for control of the Caucasus region, which is increasingly important as an energy transit route.
This tension has been heightened by Georgia's pro-western government, and more recently its application to become a member of Nato, which would bring western forces right up to Russia's borders.