MOSCOW On wooded hillsides where Georgian and separatist troops eye each other through the sights of their guns, the smallest spark could set off a war.
Last week the detention of four Georgian soldiers in the breakaway South Ossetia region quickly escalated into a crisis. Georgia threatened an attack on the Russian-backed separatists and in response Moscow sent fighter jets into Georgian airspace 'to cool hot heads in Tbilisi'.
Georgia's pro-Western government, the separatist leaders and the Kremlin say they do not want war. But with tensions at unprecedented levels, they could find themselves hostage to events on the ground.
"It's like somebody said: a couple of guys with guns could start a war in these places if they were intent on doing so," said Svante Cornell, an expert on Georgia at the Institute for Security and Development Policy, a Stockholm-based think tank.
Georgia's breakaway regions of South Ossetia and Abkhazia, both on the southern slopes of the Caucasus mountains, threw off Georgian control in separatist wars in the post-Soviet 1990s and now run their own affairs with help from Russia.
The conflicts have snowballed into an international row drawing in Russia on one side and on the other the United States, which wants to see Georgia join NATO.
Moscow and Washington are competing for influence over Georgia, an ex-Soviet state that hosts the only pipelines pumping gas and oil from the Caspian Sea to world markets without going through Russia.
On the ground in South Ossetia and Abkhazia, huge amounts of weaponry, deep-seated mistrust, unclear chains of command and the lack of any clear front line combine to create a tinderbox.
Abkhazia's main flashpoints are the Gali and Zugdidi districts, either side of the separatists' de facto border with Georgia. Four people were killed this month by a bomb in a cafe in Gali that the separatists blamed on Georgia.
Weapons are everywhere, and not just in the hands of formal security forces.
"We have buried arms wherever we could," Ruslan Kishmaria, the top separatist official in Gali district, told a Reuters reporter on a visit to the region earlier this year.
"There is probably not a single family which does not have two or three guns hidden somewhere. Oiled and cleaned and ready," said Kishmaria.
Irregular armed groups that fought on the Georgian side in the 1990s war, known under names such as the Forest Brothers and White Legions, have become active again since the start of this year, some observers say.
South Ossetia is even more volatile. It is an untidy patchwork of Georgian and separatist enclaves with shifting boundaries and often just a few meters (yards) from each other.
The ethnic Georgian village of Tamarasheni is hemmed in on three sides by separatist-controlled territory.
Georgian security forces equipped with Western-made weapons patrol in sight of a South Ossetian checkpoint, and local people showed a Reuters reporter the bullet holes in their houses from night-time gunfights.
Russian troops patrol both South Ossetia and Abkhazia under a peacekeeping mandate. Diplomats say they do a reasonable job keeping the sides apart, but they are not fully effective because Georgia sees them as a party to the conflict.
The peacekeepers in Abkhazia include a unit from the Vostok battalion, a force made up of Chechen soldiers. This has angered Georgia as fighters from Chechnya fought on the Abkhaz side in the separatist war.
Since 2006, local Abkhaz and Georgian commanders had been holding weekly meetings on a ceasefire line, meetings that acted as a safety valve for security issues. These are now suspended.
"With the dispute between Georgia and Russia in a new, dangerously confrontational phase, the risk of war in the South Caucasus is growing," the International Crisis Group, a Brussels-based think tank, said in a report this year.
"A localized provocation or an accident could cut across the calculations of all sides."