Many factors are involved in the present conflict but the central one is straightforward: the majority of the Ossetes living south of the main Caucasus range in Georgia wish to unite with the Ossetes living to the north, in an autonomous republic of the Russian Federation; and the Georgians, regarding South Ossetia as both a legal and an historic part of their national territory, refuse to accept this.

Twice in the past century, when the empire to the north weakened and Georgia declared its independence, the southern Ossetes revolted against Georgian rule. It happened in 1918-20, between the collapse of the Russian empire and the Soviet Union’s conquest of Georgia in 1921; and it happened again in our own time with the fall of the Soviet Union.

In 1918-20, between 5,000 and 15,000 people died, depending on whose figures you believe. For the conflicts since 1990, the figure is about 4,000 and rising.

As the Soviet Union began to crumble in 1989, and Georgian nationalist moves for independence gathered pace, so too did Ossete nationalism and demands for separation from Georgia.

The Ossete national movement was encouraged by the Soviet Government in an effort to exert pressure against Georgian independence.

In November 1989 the Soviet assembly of the South Ossetian autonomous region passed a motion calling for union with North Ossetia. Thousands of Georgian nationalists marched on Tskhinvali, the South Ossetian capital, in protest but were blocked by Soviet forces.

A year later, after the election in Georgia of a pro-independence government led by the extreme nationalist Zviad Gamsakhurdia, the same assembly declared South Ossetia a Soviet republic separate from Georgia. The Gamsakhurdia Government then sent thousands of Georgian armed police and nationalist militia into the region. These were fought to a standstill by local Ossete militia backed by Soviet Interior Ministry troops.

I was in Georgia at the time, reporting for The Times, and could hardly have imagined that this obscure conflict would one day create a major international crisis. Tskhinvali was a typical grey Soviet Caucasian Nowheresville, of bleak, crumbling concrete offices, potholed roads and faceless compounds. The only colour I remember was on the uniforms of the Georgian fighters: one was wearing a blue and white bobble hat, another had made for himself the uniform of an officer in the Georgian forces of 1918-21.

The Russian conscripts by contrast were not colourful at all: drab, demoralised and loathing the whole situation. They were, however, much better armed than the Georgians -- and still are today.

The conflict rumbled on for several years, with peaks of fighting interspersed with truces. When in 1991 the Soviet Union collapsed and Georgian independence (within the borders of the Georgian Soviet Republic, and therefore including South Ossetia and Abkhazia) was recognised by the international community, South Ossetia rejected this and continued to assert its independence. Georgia declared the South Ossete autonomous republic abolished.

Russia has not recognised this, but Russian forces have remained as the de facto defenders of the South Ossetian separatist region.

In 1996 the Organisation for Security and Cooperation in Europe (OSCE) brokered an agreement whereby Russian and Georgian peacekeepers would patrol different sectors of the region.

The OSCE remained until the Georgian Government of Eduard Shevardnadze, the former Communist leader, was overthrown in the Rose Revolution and replaced by the radical nationalist administration of Mikhail Saakashvili.

Russia’s policy is driven by a mixture of emotion and calculation. The Russian security establishment likes the Ossetes, who have been Russian allies for more than 250 years. They loathe the Georgians for their anti-Russian nationalism and alliance with the US. For a long time they hoped to use South Ossetia initially to keep Georgia within the Soviet Union and later in a Russian sphere of influence.

That Russian ambition has been abandoned largely in the face of the Georgians’ determination to escape from this influence.

What remains is an absolute determination not to be defeated by Georgia and not to suffer the humiliation of having to abandon Russia’s South Ossete client state, with everything that this would mean for Russian prestige in other areas. Vladimir Putin’s Kremlin made it clear again and again that if Georgia attacked South Ossetia, Russia would fight. Georgian advocates in the West claimed that Moscow was only bluffing. It wasn’t.