FACTBOX: Scenarios for Georgia's South Ossetia crisis

(Reuters) - Fighting raged in and around the capital of Georgia's breakaway South Ossetia region on Friday as Georgian troops, backed by tanks and warplanes, pounded separatist forces in a bid to re-take control of the territory.

The following are possible scenarios:

* Georgia, whose army and reservists total around 18,000 soldiers, swiftly completes its assault on breakaway South Ossetia before Russia can mobilize a major military response.

A Georgian victory could spark an exodus of non-Georgians to Russia. The majority of the breakaway region's roughly 70,000 population feel close to Russia and are ethnically distinct from Georgians.

Should Georgian troops quickly establish control over the territory it could prove more difficult for the Russians, diplomatically, to seize back control of the province by sending in its own forces.

* Failure by Georgia to quickly establish full control over South Ossetia could allow Russia, which has a peacekeeping mandate in the region, time to launch a counter-offensive, arguing that it needs to protect its own peacekeeping forces as well as civilians, most of whom have Russian passports.

Georgian officials say Russian armor is already pouring into the region from across the border. Hundreds of volunteers from Russia and another Georgia's breakaway region of Abkhazia, were reported to be making their way to South Ossetia.

* If Georgian troops fail to retake South Ossetia, Tbilisi could be vulnerable to political and diplomatic pressure from the United States and Europe to halt its offensive. The European Union is wary of antagonizing Russia, one of its main sources of energy. Some European members of NATO, also wary of President Mikheil Saakashvili's record in clamping down on opponents, have resisted moves to put Georgia on a fast track to membership. Russia fiercely opposes NATO membership for its former Soviet satellite.

* Outright defeat for Georgian forces, with a retreat to pre-conflict positions, would be a humiliation for Saakashvili. He has made it a priority to win back control of South Ossetia and Abkhazia, another rebel region on the Black Sea. Defeat could also boost his domestic opponents and raise doubts about Georgia's pro-market reforms and drive to align itself more closely with the West.