The approach helped turn the tide of insurgency in Iraq. But in Marja, where the Taliban seem to know everything — and most of the time it is impossible to even tell who they are — they have already found ways to thwart the strategy in many places, including killing or beating some who take the Marines’ money, or pocketing it themselves.

Just a few weeks since the start of the operation here, the Taliban have “reseized control and the momentum in a lot of ways” in northern Marja, Maj. James Coffman, civil affairs leader for the Third Battalion, Sixth Marines, said in an interview in late March. “We have to change tactics to get the locals back on our side.”

Col. Ghulam Sakhi, an Afghan National Police commander here, says his informants have told him that at least 30 Taliban have come to one Marine outpost here to take money from the Marines as compensation for property damage or family members killed during the operation in February.

“You shake hands with them, but you don’t know they are Taliban,” Colonel Sakhi said. “They have the same clothes, and the same style. And they are using the money against the Marines. They are buying I.E.D.’s and buying ammunition, everything.”

One tribal elder from northern Marja, who spoke on condition of anonymity for fear of being killed, said in an interview on Saturday that the killing and intimidation continued to worsen. “Every day we are hearing that they kill people, and we are finding their dead bodies,” he said. “The Taliban are everywhere.”

The local problem points to the larger challenges ahead as American forces expand operations in the predominantly Pashtun south, where the Taliban draw most of their support and the government is deeply unpopular.

In Marja, the Taliban are hardly a distinct militant group, and the Marines have collided with a Taliban identity so dominant that the movement appears more akin to the only political organization in a one-party town, with an influence that touches everyone. Even the Marines admit to being somewhat flummoxed.

“We’ve got to re-evaluate our definition of the word ‘enemy,’ ” said Brig. Gen. Larry Nicholson, commander of the Marine expeditionary brigade in Helmand Province. “Most people here identify themselves as Taliban.”

“We have to readjust our thinking so we’re not trying to chase the Taliban out of Marja, we’re trying to chase the enemy out,” he said. “We have to deal with these people.”

The Marines hoped the work programs would be a quick way to put to work hundreds of “military-aged males,” as they call them. In some places, that has worked. But the programs have run into jeopardy in other parts of Marja, an area of about 80 square miles that is a patchwork of lush farmland and small bazaars and villages.

In northern Marja, the biggest blow came when the local man hired to supervise the work programs was beaten by the Taliban and refused to help the Marines any more. The programs are “completely dead in the water” there, Major Coffman said.

In addition to work programs, the Marines are using compensation payments to build support for the newly appointed district governor of Marja, Hajji Abdul Zahir, telling people that to receive money they must get his approval. That effort has proved equally vulnerable.

In late March, an Afghan man was beaten by the Taliban hours after he had gone to the Marine outpost that houses Mr. Zahir’s office to collect his compensation. The Taliban took the money and stole a similar amount as punishment, said Colonel Sakhi, the police commander.

“My greatest fear right now is not knowing if I have put money into the pockets of the Taliban,” Major Coffman said.

Despite those reservations, the Marine strategy depends on sowing this community with buckets of cash. The money is a bridge to a day when, in theory, the new Marja district government will have more credibility than the Taliban.

That would be a difficult goal even if the Americans did not intend to rid the region of its lucrative poppy crop. While the United States has abandoned the policy of widespread eradication of the crop, efforts to discourage planting it will still cost farmers and power brokers huge sums.  

“There are lots of people with lots of money invested here, and they are not just going to give that up,“ General Nicholson said. “Now is the heavy lifting. We have to convince a very skeptical population that we are here to help them.”

 A steady flow of Taliban attacks have added to the challenge. After the February offensive, the Marines used cash payments to prod more than 20 store owners at one bazaar in northern Marja to open their doors, a key to stabilizing the area and reassuring residents.

By late March, all but five shops had closed, Major Coffman said. A prominent anti-Taliban senior elder was also gunned down in northern Marja, prompting most of the 200 people in his district to flee.

“They have completely paralyzed all the folks here,” Major Coffman said.

In another sign of how little the Marines control outside their own outposts, one week ago masked gunmen killed a 22-year-old man, Hazrat Gul, in broad daylight as he and four other Afghans built a small bridge about a third of a mile from a military base in central Marja.

Mr. Gul’s boss, an Afghan who contracted with the Marines to build the bridge, says he has been warned four times by the Taliban to stop working for the Americans.

And even as the NATO-backed Mr. Zahir struggles to gain credibility as Marja’s leader, the Taliban are working to fortify their own local administration.

According to Colonel Sakhi, the Taliban’s governor for Marja returned to the area on Monday for the first time since the February assault and held a meeting with local elders, many of whom Mr. Zahir is trying to win over. The Taliban governor warned them not to take money from the Marines or cooperate with the Afghan government, Colonel Sakhi said.

In central Marja, where the work projects have had more success, about 2,000 Afghan men are employed by programs financed by the First Battalion, Sixth Marines, said the unit’s civil affairs leader, Maj. David Fennell.

At one of the battalion’s outposts, shipments of cash arrive regularly. The last was 10 million afghanis, or $210,000, stuffed into a rucksack. The battalion doles out $150,000 a week, Major Fennell said.

On one afternoon in late March, 40 Afghans could be seen clearing away several acres of rubble remaining from a bazaar leveled during a NATO bomb strike two years ago. The $190,000 contract is expected to take a month to complete.

But intimidation is still rife — even inside the walls of the Marines’ outpost. One woman who came to the base crouched behind a Humvee and begged for help, saying that her husband had been killed during the February operation.

First Lt. Aran Walsh offered her $1,700 worth of Afghan currency. He asked her why she hid herself.

“If they see me, they’ll inform the Taliban,” she said.

Moises Saman contributed reporting from Marja, and Taimoor Shah from Kandahar, Afghanistan.