The soldiers looked at one another. What should we do? Should we detain them? For what? For walking in their own country? Garner stood on a boulder above the women, looking down at them. One woman signaled with her hand, asking if her group could pass by. She pointed at a Claymore. The mine was hidden, but when you lived in a country covered with explosives, you learned to watch where you walked.

Garner signaled for her to pass by; she shook her head no and pointed in a different direction she wanted to travel, circling around their makeshift camp, hugging the cliff and walking into a thick cluster of woods. They allowed the women to leave on that route.

As the sun set on the valley, Cunningham, Monti, and Hawes stood behind a big rock and began talking about moving to a different spot. If they did, they would have to travel on a different path -­ that's how the enemy slays U.S. soldiers, Cunningham thought, he waits until we're in a vulnerable position. Yet they weren't sure there was a better, more defendable position -­ this area of the ridgeline was wider than others, and there were a few big boulders they could use for cover.

They were talking about doubling the number of troops on guard shift for the night when an RPG exploded in the tree above them.

* * *

There are many different types of grenades and RPGs, but in general one should picture an RPG as resembling arocket about the size of a man's forearm. Fired from a tube, it becomes something like a combination of an immense bullet and an explosive. RPGs take down helicopters; they stop tanks. Human bodies -- flesh and bone, muscle and tissue -- offer little impediment.

First comes the force of the explosion, the blast wave that inevitably knocks soldiers down and perhaps unconscious. The high-pressure shock wave is followed by a "blast wind" that sends an overpressure through the body, causing significant damage to tissues in the ears, lungs and bowels.

Then, if a soldier survives being hit by an RPG, it's only after he has gotten his bearings that he then notices the impact of the considerable shrapnel. The RPG casing, now in the form of myriad penetrating fragments, has been hurled in all directions. That the shape of these fragments is irregular can slow down their trajectory as they fly through tissue, at times making their impact more painful than a bullet. A leg or arm might be turned to mash, or liquefied. If you're a soldier in battle and an RPG hits a tree near you, you get down and hope to God that another one doesn't land closer.

* * *

The first thing Smitty did was look at his watch to see what time he was going to die. Private 1st Class Sean "Smitty" Smith had been lying down and putting out his cigarette ­- a local brand called Pine Light ­- when the shooting started. He and six other troops were at the northern end of their position, near the treeline. The other five were Franklin Woods, Brian Bradbury, Private 1st Class Derek James, Specialist Matthew Chambers, and Specialist Shawn Heistand. Woods had heard the shuffling of feet, but before he could say anything the shooting started, so quickly and so ferociously that many of the troops didn't even have time to grab their weapons. There were approximately 50 Afghans shooting at them from 150 feet away to the north, and some more immediately to the west -- all so close that the men at the treeline could see the their faces as they fired at the Americans with Russian-made PKM machine guns. Those faces looked calm and collected, wearing the kind of expression common to target practice. The insurgents firing the RPGs were to the northwest.

A U.S soldier climbs a hilltop near the town of Walli Was in Paktika province. (Goran Tomasevic/Reuters) A U.S soldier climbs a hilltop near the town of Walli Was in Paktika province. (Goran Tomasevic/Reuters)

Smitty was scared. This was his first firefight ever. There wasn't much for him to take cover behind, though he didn't think the enemy yet knew he was there. But sooner or later, they would surely figure it out.