By Rajiv Chandrasekaran in Camp Leatherneck, Afghanistan

US marines began fanning out across the valley of the southern River Helmand on Thursday, travelling on foot and in armoured convoys under the scorching sun to wrest control of the area from Taliban insurgents.

Marine commanders rep­or­ted only modest resistance from insurgent fighters as the troops poured out of helicopters in the early morning and began conducting patrols. Some units encountered light small-arms fire and one marine company was attacked with rocket-propelled grenades after it discovered a cache of homemade explosives in a housing compound.

There were no reports of marine casualties resul­ting from insurgent attacks.

“It’s going remarkably well so far,” said Colonel Eric Mellenger, the operations officer for the 2nd marine expeditionary brigade, which is conducting the operation.

One battalion moved into the Nawa district of Helmand, to the south of the provincial capital, Lashkar Gah. Another established footholds farther south, in the district of Garmser.

The mission, invol­ving 4,000 marines, is the first large test of the US military’s counterinsurgency strategy. The marines, along with an army brigade scheduled to arrive this summer, plan to push into pockets of the country where Nato forces have not been able to maintain order.

Officers said the mission, months in the planning, is the marines’ largest operation since the 2004 invasion of Falluja, in Iraq.

The two districts that are the initial focus of the operation, Nawa and Garmser, have long been Taliban strongholds. Although British troops serving under Nato’s Afghan command have waged several battles against the insurgents in both areas over the past three years, the British lacked sufficient forces to maintain a significant presence in the districts.

Marine commanders said before the start of the operation that they expected only minimal Taliban opposition at the outset but that assaults would probably increase once forces moved into towns and began patrols. Troops have been told to prepare for suicide attacks, ambushes and roadside bombings.

“They’ve backed off for now but there will almost certainly be more attacks to come,” said Colonel Burke Whitman, who serves as a liaison officer to the Afghan security forces. “They’re waiting to see what we do.”

As marine units arrive in their designated towns and villages, they have been instructed to build and live in small outposts among the population. The brigade’s commander, Brigadier General Lawrence D. Nicholson, said his marines would focus their efforts on protecting civilians from the Taliban and on restoring Afghan government services, instead of mounting hunt-and-kill missions against the insurgents.

“We’re doing this very differently,” Gen Nicholson said to his senior officers before the mission began. “We’re going to be with the people. We’re not going to drive to work; we’re going to walk to work.”

An initial priority for the marines will be to bring back Afghan government officials and reinvigorate the local police forces. marine commanders also plan to help district governors hold shuras, or meetings of elders in the community, in the next week.

“Our focus is not the Taliban,” Gen Nicholson told his officers. “Our focus must be on getting this government back up on its feet.”

But Gen Nicholson and his top commanders recognise that making that happen involves tackling num­erous challenges, starting with the lack of trust among the population. That mistrust stems from concern over civilian casualties resulting from US military operations, as well as from the fear that the troops will not stay long enough to counter the Taliban.

The marines have also been vexed by a lack of Afghan security forces and a near total absence of additional US civilian reconstruction personnel.

To compensate in the interim, the marines are deploying what officers say is the largest ever military civilian-affairs contingent attached to a combat brigade, about 50 marines, mostly reservists, with experience in local government, business management and law enforcement.

Once basic governance structures are restored, civilian reconstruction personnel plan to focus on economic development programmes, including helping Afghans grow legal crops.

“We’re not going to measure your success by the number of times your ammunition is resupplied ... Our success in this environment will be very much predicated on restraint,” Gen Nicholson told a group of officers from the 2nd battalion, 8th marines. “You’re going to drink lots of tea. You’re going to eat lots of goat. Get to know the people. That’s the reason why we’re here.”