BAGHRAN VALLEY, Afghanistan – American soldiers descended on a mountain ridge yesterday, quickly setting up fortified posts and mortar positions overlooking a key Taliban transport route as the coalition pressed a major offensive that has killed dozens of suspected terrorists.

It was the first time in several years that soldiers from the American-led military force have ventured into Baghran Valley in the northern part of Helmand province.

Troops from the 2nd Battalion, 87th Infantry Regiment, 10th Mountain Division poured out of CH-47 Chinook helicopters in the early morning and scouted the mountain for militants.

The position will allow American forces to block the movement of Taliban fighters and supplies, said one of the officers, Lieutenant Colonel Chris Toner.

More than 10,000 coalition soldiers are spread out over four southern provinces – Helmand, Uruzgan, Kandahar, and Zabul – in Operation Mountain Thrust, a blitz aimed at quelling a surge of Taliban attacks. It is the largest offensive since the 2001 ouster of the Taliban regime.

“We are the focus of Mountain Thrust right now,” said Captain Jared Wilson. “This is the decisive part of the operation because if we do not get on the mountain, we will not be able to accomplish this mission.”

Before boarding the helicopters, Captain Wilson warned his troops about the dangers of the operation.

“I want you to understand the seriousness of what you are about to do. We are landing fully loaded CH-47s on the top of a mountain. This is a highly dangerous mission. On the top of those dangers, we’re going to an area where no one has been for years,” he said.

Their new encampment is remote – more than 60 miles from the nearest ground forces – but Captain Wilson said that serves as an advantage.

“The enemy did not suspect we would come up here. They believe they have a safe haven area up here because it has been untouched by coalition troops for years,” he said.

Once down on the mountain ridge, soldiers went to work setting up defense positions and firing mortar rounds into the valleys to test their equipment and check ranges.

Standing guard with an M-16 rifle on a ridge line, Specialist Daniel Borisow, 23, from Akron, N.Y., looked down into the valley at a smattering of mud huts. He said he was ready to fight.

“For once we are in the position where we’re going to take the fight to the enemy instead of us rolling through (in Humvees) and them attacking us,” he said.

The open-ended offensive aims to hunt down Taliban fighters blamed for an onslaught of ambushes and bombings in recent months, the worst spate of militant violence since 2001.

More than 500 people – most of them terrorists – have been killed in the past month as insurgents launched increasingly bold attacks on coalition forces. More than 90 suspected terrorists have been killed the past few days, the coalition says.

At least nine coalition soldiers have been killed since mid-May.

Yesterday, Taliban terrorists fatally shot a former chief of one of Helmand province’s districts and four of his bodyguards in an ambush of their convoy, provincial spokesman Ghulam Mohiudin said. The official, Jama Gul, was traveling between Sangin and Grishk districts.

Southern Helmand was also the scene of fighting Saturday, when British troops killed six Taliban fighters near Kajaki dam, a British spokesman, Captain Drew Gibson, reported yesterday.