After 10 years at war, coalition forces are still struggling to bring peace to Afghanistan.
In some places, the effort is being undermined by tribal rivalries that draw away attention and resources.
Dominating tribes
The main road that runs through Achin district of Afghanistan is closed to all traffic except border police. It is near the vital highway that links Pakistan's Khyber Pass to the Afghan capital, Kabul.
The Shinwari tribe dominates Achin and two sub-tribes, the Sepai and Ali Sher Khel, live on either side of the road.
They are at war with each other.
Defense
During the day, tribesmen guard their territory. At night, they hide behind rock mounds that cover the land and fight.
Sayeed Hakim from the Ali Sher Khel tribe says that, because of the fighting, they have moved many of their women and children out of the area.
He says when we sit here in our village; we sit close to the walls where our animals are. We take cover with these walls. We find a place where the bullets cannot hit us directly.
The dispute has gone on for years, but has escalated in recent months.
Malik Mahamoud is a tribal leader from Sepal who says just yesterday tribal leaders said that if the fighting continues, the insurgents will use it to their advantage, undermining security and attacking coalition forces.
Conflict
In January 2010, Achin did not appear headed for conflict. The Shinwari tribe had pledged to support the Afghan government, oppose the Taliban and ban opium growing. In return, U.S. commanders pledged $200,000 for small development projects and promised an additional $1 million for future projects.
To try to minimize corruption, the senior U.S. commander in eastern Afghanistan decided to disperse the aid through the local government and fund projects approval by a tribal shura.
But bypassing the central government drew complaints from senior Afghan officials who argued it undermined the Karzai administration. The U.S. State Department later drafted a policy prohibiting officials from working with tribes. The promised aid was never distributed.
Since the pact fell apart, all schools in Achin have closed, the only clinic has shut its doors and the local bazaar is deserted.
Taliban
While some tribal leaders say despite their dispute, they are continuing to keep out the Taliban, others concede they are accepting help from insurgents.
An Ali Sher Khel tribesman, who asked not to be named because he fears retribution for speaking out, says the Shinwari's reliance on the Taliban boils down to money.
He says when there is fighting we have to buy weapons. Our harvest just lies in the field because we cannot collect it peacefully. He says we are losing money and because of the dispute, we have contact with the Afghan Taliban. They help financially and with weapons.
The ongoing fighting is draining critical resources away from other missions. Some 600 Afghan police protecting the border area near Pakistan are now in Achin trying to contain the violence.
General Aminullah Amerkhil, the border police commander in eastern Afghanistan, says there are powerful forces behind the land dispute. On one hand, the dispute is a political issue and, on the other, the Taliban have taken advantage of the situation. The Taliban is not only threatening Jalalabad, he says, but the entire eastern region of Afghanistan.
Members of the Sepai and Ali Sher Khel tribes say they want the government to resolve their differences, but little is being done. Both sides threaten to join the insurgents if the government does not step in. But, for now, they continue fighting and the Taliban keeps encouraging them.