IT was seeing American soft drinks in Al-Qaeda hands that made Second Lieutenant Eric Schwartz really angry. "They were wearing our US Army uniforms, our ponchos and swigging from Snapple bottles as if to taunt us," he said, describing one of the many ambushes on his unit in the southeastern Afghan town of Shkin.

"Others had cloaks covering their bandoliers of bullets so we would think they were civilians. They were Chechens and Waziris and they fight dirty.

"You know, a lot of people outside think the war here in Afghanistan is over, but we're on the ground and I'm telling you this is where the war on terrorism really is and it's getting harder."

"Welcome to Shkin", reads the hand-painted sign where a black Chinook touched the ground last week, churning up thick clouds of dust with its whirring blades. Another was just behind. Helicopters fly in pairs and never turn off their engines at this US base high up in the badlands between Afghanistan and Pakistan, hovering just long enough to disgorge one lot of American troops and load the next.

All the time a smaller Black Hawk patrols the sky. "Trust me, you don't want to be here," said Bruce Capehart, a combat psychiatrist among those jumping on board to leave.

"The most evil place on earth" is how Shkin is described by Colonel Rodney Davis, a spokesman for the US forces in Afghanistan. "Real Mad Max territory."

It is here, in these fortress-like mountains, that the search for Osama Bin Laden is now concentrated. In the past six weeks it has seen some of the heaviest fighting of the whole war in Afghanistan.

Perched on a desolate hill from which the Pakistan border post is visible on the facing mountain, the mud-walled base surrounded by coiled barbed wire looks exposed and primitive. Indeed, the soldiers of the 10th Mountain Division stationed here often go for days with no water.

But there is nothing unsophisticated about the control room where officers pore over maps marked "classified", monitor radio frequencies used by Al-Qaeda operatives, study satellite images and download intelligence gleaned from prisoners and cross-checked at the Harmony database at Bagram, the centre of American operations in Afghanistan.

Sipping black coffee from a paper cup at his desk, the commander, with small lines of tiredness etched around his eyes, has little doubt about what he and his men are up against. There is no talk here of that other war in Iraq.

"This is the real front line in the war against terror," said Colonel Michael Howard, a surprisingly soft-spoken, thoughtful man, who commands the 1,050 troops at all four American bases in the border area of southeastern Afghanistan.

US intelligence has focused the hunt for the world's most wanted terrorist on a 40-square-mile stretch just across the Pakistan border in south Waziristan, and it would seem to be the perfect hiding place. The local Pashtun people say that, when Allah created the earth, he had a pile of rocks left from which he created Afghanistan. There can be few places as hostile as the tribal lands that straddle the
border.

In the summer there is no shade from the harsh 120F sun, while in the winter the sub-zero winds seem to pierce the bones. Gritty dust coats everything, getting into the mouth, hair, ears and eyes, and under the fingernails. All the soldiers seem to have grey complexions and at night the tents echo with hacking coughs.

Explore World News

• World Agenda

• Iraq News

• US & Americas News

• Europe News

• Middle East News

• Afghanistan News

• Asia News

• Africa News

• Ireland News

Times Recommends

• UN may halt 400-year-old 'freedom of the seas'
• Where the Rosetta belongs can’t be set in stone
• Gas deal on hold, but Ukraine may pay in the end