By Damian Grammaticas
BBC News, Khost, Afghanistan
Another helicopter brings more casualties
The call is a red alert, and American medics scramble to meet an incoming helicopter.
It is ferrying the latest casualty from Afghanistan's vicious, changing war.
He is stretchered straight into the field hospital in forward base Salerno at Khost close to the border with Pakistan.
His name is Staff Sgt Ken Wininger, and the bones in his foot have just been shattered by a roadside bomb.
"A big old flash of black came across the windshield," he says, describing the moment his vehicle was hit.
"I crawled out of the truck, my gunner and my driver were yelling that they were okay, and I yelled that I was okay. But my foot hurt. I noticed the front wheel of the Humvee was lying about a hundred metres away."
The doctors treating Staff Sgt Wininger say his war is over. It will take months of operations and therapy to repair his foot. He will never sprint again and never be able to carry heavy weights.
Staff Sgt Ken Wininger was injured in a bomb attack on his vehicle
A Taleban propaganda film shows attacks like the one that destroyed Ken Wininger's vehicle.
A Humvee is seen driving down a remote road. There is a huge blast. The gunner in the turret is thrown up into the air and the seven-tonne vehicle topples over backwards.
The Taleban appear to be copying tactics from Iraq - becoming more deadly.
In the propaganda film masked men prepare a homemade bomb the size of a football. It is crude, but lethal - powerful enough to blow apart an armoured vehicle.
Instead of confronting America's firepower head on, the Taleban are attacking more exposed targets, like unarmoured vehicles belonging to the Afghan army, police stations, government buildings.
While we were patrolling with the Americans a suicide bomber detonated his explosives at the police checkpost on the river crossing right next to the city of Khost.
The blast left a crater in the tarmac, shrapnel marks across the face of the building and the smouldering wreckage of two cars caught in the explosion.
A couple of policemen were injured, one lorry driver was killed.
Increasingly this is the way the Taleban are fighting their war. They cannot gather in large formations because they will be decimated by Nato's modern war-fighting armies. So the Taleban are waging a guerrilla campaign.
The police in Khost showed us a suicide vest they had captured a few days ago.
Rafiq (left) tried to kill Khost Governor Arsala Jamal
It was wired and ready for use, packed with 30kg of explosives.
The bomber had been recruited in the madrassas of Pakistan and sent across the border on his suicide mission.
Most of the Taleban's suicide bombers are teenage boys. Rafiq is just 14 years old.
"We were told Afghanistan is full of infidels," he says. "They said if we become martyrs we go straight to heaven, and there we have anything we want."
But there is no paradise for Rafiq, just embarrassment, as he stands awkwardly posing for pictures with his intended target, Khost Governor Arsala Jamal, who has escaped three suicide attacks.
"I feel sorry for him," says the governor. "In Khost, for sure, the Taleban don't have the support of the masses. They don't have the ability to fight with our security forces face-to-face. That's why they are going for these extreme tactics."
Teenage bombers and homemade explosives may not be enough to win the Taleban this war, but they are effective and hard to combat.
The Americans have lost 50 men in Afghanistan so far this year. Every new casualty bleeds a little more strength from the coalition.