By Tom Coghlan
US forces have refined strategy to tackle border incursions
By night, Salerno is filled with the clatter of rotor blades as unlit helicopters carry troops on clandestine missions to the Pakistan border, just 14km away.
Salerno is the US operations base in Afghanistan's Khost province, south-east of the capital, Kabul.
Over the past two months, US commanders say, increased cooperation with the Pakistan military has allowed them to exert unprecedented pressure on al-Qaeda and Taleban militants in the region.
Back in February, one US commander had predicted cooperation between US and Pakistani forces would develop a "hammer and anvil approach" along the Afghan border.
The pronouncement was little publicised in Islamabad, where the deployment of regular Pakistani troops to its semi-autonomous Federally Administered Tribal Areas was one of huge political sensitivity.
Now, says Col Gary Cheek, commander of the combined task force at the Salerno Forwarding Operations Base, there is a big difference because "the Pakistani army is now on the other side of the border".
"My impression is they have come from the interior and they are continuing to move up to the north," he says.
Col Cheek contrasts the "tremendous allies" in the regular Pakistani army with the "questionable allegiances" of some of the Pakistani border scouts, their previous point of contact.
In the past two months liaison through Pakistani army officers attached to CJTF 76 (Combined Joint Task Force), the main US headquarters in Afghanistan, has begun facilitating what the colonel calls "coordinated operations" along the border.
In another part of their evolving strategy, US forces have constructed five new border check posts, with plans for a sixth.
They are manned by mixed Afghan and US special forces.
"What they really are is battle positions," says Col Cheek.
He says they have had a "remarkable impact" on border infiltration.
The posts are frequently attacked despite their near impregnable mountaintop positions.
"We think the attacks must be some sort of initiation rite for the new Talibs [Taleban fighters]," says Captain Dutch Roell, serving with the Salerno-based 3/6 US Marines.
Significant refinements have been possible following the deployment of artillery at Salerno.
Long muzzles trained eastwards, Fox Battery 7th Field Artillery deployed last month.
The Americans say the guns have given them an all-weather fire-support capability up to and over the border.
"With our rules of engagement, we can fire across that border only with the approval of the on-scene commander if he has a hostile threat against him," says Col Cheek.
The Pakistani press reports frequent illegal troop incursions.
US commanders say their forces only manoeuvre into Pakistani territory if their safety depends upon it and only with permission from US 25th Division commander, Maj Gen Eric Olsen.
However, if US forces spot an insurgent force in Pakistan within artillery range, it can be attacked with Pakistani
"Naturally we prefer to work with the Pakistanis, and that is what happens more often than not," says Col Cheek.
Pakistan is sensitive to US aircraft flying into its air space
"If we see a force over there we will contact [the Pakistani liaison officers]. They are pretty rapid. Sometimes they say to us, 'go ahead we have no issues with you firing'."
The Americans have found that there is less sensitivity to cross-border artillery than there is to aircraft straying into Pakistani airspace.
Improving relations have seen Pakistani complaints drop from an average of two written complaints a week and daily reports of infringements to almost nothing.
US planners had expected a surge in militants crossing the border because of recent Pakistani offensives in neighbouring Waziristan. But that has not happened, the Americans say.
Nor did cross border infiltration increase ahead of last weekend's election, Col Cheek said.
"I think the Pakistani military has been successful and this will show that the insurgency may not be as grand as many make it out to be."
It is impossible to say at present, but it may be that many militants have simply melted away southwards towards the sprawling anonymity of cities like Karachi.