NAWA, Afghanistan — In three combat tours in Anbar province, Marine Sgt. Jacob Tambunga fought the deadliest insurgents in Iraq.
But he says he never encountered an enemy as tenacious as what he saw immediately after arriving at this outpost in Helmand province in Afghanistan. In his first days here in late June, he fought through three ambushes, each lasting as long as the most sustained fight he saw in Anbar.
Like other Anbar veterans here, Tambunga was surprised to discover guerrillas who, if not as lethal, were bolder than those he fought in Iraq.
"They are two totally different worlds," said Tambunga, a squad leader in Company C, 1st Battalion, 5th Marines.
"In Iraq, they'd hit you and run," he said. "But these guys stick around and maneuver on you."
They also have a keen sense of when to fight and when the odds against them are too great. Three weeks ago, the U.S. mounted a 4,000-Marine offensive in Helmand -- the largest since President Barack Obama's troop increase -- and so far in most places they have encountered less resistance than expected.
Yet it is also clear to many Marines and villagers here that Taliban fighters made a calculated decision: to retreat and regroup to fight where and when they choose. And in the view of troops here who fought intensely in the weeks before the offensive began, fierce battles probably lie ahead if they are to clear Taliban from sanctuaries so far untouched.
"It was straight luck that we didn't have a lot more guys hit," said Sgt. Brandon Tritle, another squad leader in Company C, who cited the Taliban's skill at laying down a base of fire to mount an attack.
"One force will put enough fire down so you have to keep your heads down, then another force will maneuver around to your side to try to kill you," he said. "That's the same thing we do."
In other parts of Helmand, the Taliban have been quick to mount counterattacks. Since the offensive began, eight Marines have been killed, mostly south of Garmser in areas thick with roadside bombs. In addition, British forces in Helmand, who usually travel in lightly armored vehicles, have lost 18 men, all but two from bombs.
All told, Western troops have died in greater numbers in Helmand this month than anywhere else in Afghanistan since the 2001 invasion.
It is unclear whether the level of casualties will remain this high. But the Taliban can ill afford to lose the Helmand River valley, land made arable by canals that nourish the nation's center for poppy-growing.
"This is what fuels the insurgency," said Brig. Gen. Larry Nicholson, commander of the Marine brigade leading the offensive.
For now, the strategy of the Taliban who used to dominate this village, 15 miles south of the provincial capital of Lashkar Gah, is to watch and wait just outside, villagers and Marines say.
"They all escaped," said Sardar Gul, a shopkeeper at the Nawa bazaar. Gul and others who reopened stores after the Marines arrived estimate that 300 to 600 Taliban fled to Marjah, 15 miles to the west and not under U.S. control, joining perhaps more than 1,000 fighters.
Marine commanders acknowledge they should have focused more on cutting off escape routes early in the operation, an issue that often dogged offensives against insurgents in Iraq.
In contrast to Iraqi insurgents, the Taliban do not seem to have access to large artillery shells and other powerful military munitions that Anbar fighters used to kill hundreds of Marines and soldiers. The bombs found so far have been largely homemade with fertilizer, though they have still killed more than 20 British soldiers and U.S. Marines to the north and south of Nawa.
"If they had better weapons, we'd be in real trouble," said Lance Cpl. Vazgen Matevosyan.