GARMSER, Afghanistan -- Gunfire zings in near Sgt. Dan Linas' patrol, pinning down his squad against a dirt berm. The Marines peer across the field to their left, at three mud huts and a grove of trees, searching for the muzzle flash. Then they cut loose with their M-16s.
The sun is barely up, but for the men of Bravo Company's 2nd Platoon, the firefight proves just the first in a series of skirmishes Friday that will see Marines unleash earsplitting barrages of machine gun fire, mortars and artillery, most of which land just 600 yards away.
To the east, north and south lie bountiful fields of opium poppies, to the west an unseen enemy.
Airstrikes and artillery have thundered around this southern Afghan town all week, since several companies of the 24th Marine Expeditionary Unit took the offensive before dawn Tuesday and swept into Garmser, which sits in Taliban territory into which no NATO troops had ventured.
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The British military is responsible for Helmand province, but its 7,500 soldiers, along with 2,500 Canadian troops in neighboring Kandahar, haven't had enough manpower to tame Afghanistan's south.
So, the 2,400-strong 24th Marines have come to help.
The push into Garmser is their first mission since arriving from the United States last month, and it is the farthest south that American troops have been in several years. Most of the 33,000 U.S. troops in Afghanistan operate along the border with Pakistan.
Some of the men in the 24th Marines have seen combat in the toughest parts of Iraq, and their commanders hope that experience will help calm the Taliban insurgency in Afghanistan.
British forces are mainly in the northern part of Helmand, which is the world's biggest producer of opium poppies. Britain has an outpost on Garmser's northern outskirts, but NATO has had no presence south of that.
Mission is short term
The Marines in Garmser do not plan a long stay. They will leave the poppy fields be. Their only mission is to open the road for a Marine convoy that will move through town. They sit and defend the 10-foot-wide lane of dirt.
After returning fire from the berm across the empty field, the men under Linas -- a 21-year-old from Richmond, Va. -- jog 100 yards to the platoon command center, where Marines in the lookout post provide covering machine-gun fire.
The platoon mortar team then dials in coordinates and fires shells in high arcs toward the suspected location of Taliban fighters, throwing up puffs of smoke in the field. There is no way to tell if any militants are hit.
In the foreground, 40 yards from the Marines' post, six Afghan men work in their illegal poppy fields, slicing the bulbs to coax out opium resin that will be used to make heroin.
They look up as the mortars boom out, then go back to work.
The 24th Marines served in 2006 and 2007 in Ramadi, capital of Anbar province in western Iraq. The vast region was the stronghold of al-Qaida in Iraq before the militants were pushed out in early 2007.
Compared with the dense population centers where they fought in Iraq, Marine artillery and mortar teams have much more freedom to fire in the open spaces of rural Afghanistan, where the Taliban operate.
But before more mortars are fired, 2nd Lt. Mark Greenleaf, the 24-year-old platoon commander from Monmouth, Ill., asks his observers if any civilians are in danger. "What's the collateral damage beyond the tree line?" he barks.
The expanse to the Marine post's west has been empty for days, even as farmers have worked with their poppy plants in all other directions, an indication the Taliban have a heavy presence to the west. But the company commander, Capt. Charles O'Neill, decides he's not interested in an all-day mortar battle with the insurgents.
Moments later, the Marines hear the whoosh of a rocket being fired in the distance. Everyone rushes for cover, pushing themselves against mud walls or into trenches. The boom of an exploding missile rattles the outpost but it's a couple of hundred yards off target.
A wave of gunfire rings out as Marines react, until sergeants shout for the men to cease fire. One Marine infantryman with a team still on the berm states the obvious: "They missed."
But Lance Cpl. Matthew Cato of Simpsonville, S.C., 21, says: "I don't care, it scared the s---- out of me."
"I hate hearing those things go off, because then you're just sitting here going, 'Oh, man,' " adds Cpl. Keith Manley, 23, of Ilion, N.Y.
The heat of the noon sun settles in. Marines and militants put down their weapons and hunker down in any shade they can find.
The countryside stays quiet until a convoy of Humvees pulls up in midafternoon to evacuate a Marine with a badly swollen ankle from a sprain. As soon as the Humvees stop, incoming fire starts up.
The gunner atop one Humvee opens fire with his .50-caliber machine gun, and Marines with M-16s blaze away. After several minutes of heavy gunfire, which kicks up clouds of fine sand that sift down on the Marines, squad leaders yell for their men to conserve ammunition.
"If there's too much ... smoke to see the target, then don't waste the rounds," yells Sgt. Chris Battaglia, 28.
An artillery post outside town then joins the skirmish, sending round after round exploding 600 yards away. Marines yell for everyone to stay down.
O'Neill, the company commander, says all-day potshots by Taliban fighters are little more than nuisance attacks. The militants use binoculars and have forward observers with cell phones to try to aim better at the Marines, he says.
"This is pure asymmetric harassment," he says. "They'll pop out of a position and fire a rocket or mortar."