September - October 2007: Soldiers of Battle Company of the Second Battalion of the US 503rd Infantry Regiment fire grenades and automatic weapons from their bunker in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: US forces bomb an insurgent position with phosphorus in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: Soldiers of Battle Company of the Second Battalion of the US 503rd Infantry Regiment run to a sniper position for a counter attack after being overrun by militants during a combat operation above the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: A US helicopter lands to pick up an American commander, after a meeting in the wake of US bombing of Yaka China village in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: A mortar company of the Second Battalion of the US 503rd Infantry Regiment returns fire from the Kop base, the main US base in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around this valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: A soldier of Battle Company of the Second Battalion of the US 503rd Infantry Regiment shouts out to his gunner while preparing grenades in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: Grenades marked by a soldier of Battle Company of the Second Battalion of the US 503rd Infantry Regiment in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: Soldiers of Battle Company of the Second Battalion of the US 503rd Infantry Regiment drag an injured comrade to shelter under fire in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: A doctor of Battle Company of the Second Battalion of the US 503rd Infantry Regiment treats an injured soldier while under attack in the Korengal Valley, Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around the Korengal Valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

September - October 2007: An American soldier checks a thermal imaging machine near Kop, the main US base in the Korengal Valley in north-eastern Afghanistan. Nearly three-quarters of all bombs dropped by NATO forces in Afghanistan are dropped on and around this valley. Yet much of the fighting is on foot, and ground gained is measured in yards, single hilltops, small patches of forest.

Korengal Valley, Afghanistan. Brandon Olson, Specialist of Second Platoon, Battle Company of the Second Battalion of the US 503rd Infantry Regiment sinks onto an embankment in the Restrepo bunker at the end of the day. The Korengal Valley was the epicenter of the US fight against militant Islam in Afghanistan and the scene of some of the deadliest combat in the region.

World Press Photo of the Year - World Press Photo of the Year