By Tom Coghlan
In Ahmadabad district, Paktia province
Drums hang in the remote villages of Paktia, deep in the tribal belt of eastern Afghanistan.
At times of danger, beating the drum brings hundreds of armed local men running from their homes - an instant army to protect the area.
It is the basis for a traditional system of village militias, known as the "arbakai", that operates in only a few provinces of the east.
With Afghanistan's fledgling national police deeply unpopular and insufficient in number to impose control in many areas of the country, Western diplomats and commanders have been exploring what they term "Afghan solutions" to counter rising Taleban violence.
Britain, in particular, is exploring the use of village defence forces in Helmand province.
The idea owes much to the controversial arming of Sunni tribal militias in al-Anbar province of Iraq by American forces, which has dramatically reduced the influence of al-Qaeda in that region.
Speaking to the British parliament on 12 December, British Prime Minister Gordon Brown said that Britain advocated a shift in strategy that would favour "hard-headed realism" and work "with the grain of Afghan tradition".
"One way forward is to increase our support for community defence initiatives, where local volunteers are recruited to defend homes and families modelled on traditional Afghan 'arbakai'," he said.
Harnessing informal militias is not a new idea in counter-insurgency. But it has a mixed history of success, not least in Afghanistan.
Alongside some successful examples - such as the British use of the Firqa irregulars in Oman in the 1970s or the US forces' use of Hmong tribal militias in Vietnam - are less encouraging precedents.
After the withdrawal of Soviet forces from Afghanistan in 1989, President Najibullah surprised the world by holding out for three years against the mujahideen guerrillas.
His use of local militias initially proved successful. However, though they were sometimes tough fighters, the brutality and indiscipline of such units helped to alienate public support for his regime and they could be unreliable, self-interested and prone to switching sides.
At sunset in a village in Ahmadaba district of Paktia, in the shadow of snow-capped mountains, a group of local men stand with Kalashnikovs and a wary eye for their surroundings.
They are the local arbakai from the Ahmadzai tribe, just 10 strong but with the power to raise a force of 250 in less than 20 minutes.
"We just listen to our tribe, to our tribal elders," said Haider Jan, a wild-haired young man wearing scraps of Afghan police uniform who showed off an old Taleban bullet wound in his leg.
"We keep the Taleban out of this area. If we find someone sheltering the Taleban, the tribe will burn his house."
The system only operates in an area of eastern Afghanistan which is famous for the weakness of government influence and the strength of its tribal structures.
Officially, the arbakai of the area were incorporated into the Afghan National Auxiliary Police, a central government reserve police force formed last year. However, they regard themselves still as simply the "Ahmadzai arbakai".
In Paktia the tribes rule themselves, imposing their own legal system.
The arbakai are the police, tribal elders are the local rulers; the system as a whole is part of the ancient Afghan code of behaviour known as "Pashtunwali".
"Each sub-tribe takes its turn to be arbakai and they serve 10 days at a time," said Shaista Khan Mangal, a tribal elder in the provincial capital, Gardez.
"The arbakai only works in the area of its own tribe. The tribe will discipline them if they do anything wrong to the people.
"They recognise the local people. That is why they are better than the national police or the army."
'Back the police'
Western officials working in the region acknowledge that the arbakai system is often a substitute for central government control, and frequently preferable to corrupt centrally-appointed police.
Tribes in Paktia have their own legal system
"There are strong tribal structures in Paktia and these usually stand in opposition to the Taleban," said one Western official.
The official emphasised that the arbakai worked only where tribal structures were strong and where tribes were not mixed together.
The potential dangers that come with arming unofficial militias are clear.
Tens of millions of pounds have so far been expended on trying to disarm illegal militias across Afghanistan under two separate UN-backed programmes and to impose central government control.
And in southern Helmand province, where a number of militias tied to local warlords already operate as adjuncts to the local security forces, they have been linked to drug crime, frequent looting and murder.
But so, too, have the official police.
"I am speaking for myself, not my government here - but as far as Afghanistan is concerned in three decades of war there is not any example of a militia having done anything for the benefit of Afghanistan," said Helmand Police Chief, Gen Mohammad Hussein Andiwal.
"If you use the name of militia or of arbakai, people will be shocked. They had a very bad reputation and just look after the interests of their own tribe.
"The British have not contacted me on this issue, but I will always tell them to focus on the national police, not militias."