Signs of change have sprouted this spring amid the lush fields and mud-brick villages of southern Afghanistan.

In Sangin, a riverine area that has been the deadliest part of the country for coalition troops, a journey between two bases that used to take eight hours because of scores of roadside bombs can now be completed in 18 minutes.

In Zhari district, a once-impenetrable insurgent redoubt on the western outskirts of Kandahar city, residents benefiting from U.S.-funded jobs recently hurled a volley of stones at Taliban henchmen who sought to threaten them.

And in Arghandab district, a fertile valley on Kandahar’s northern fringe where dozens of U.S. soldiers have been felled by homemade mines, three gray-bearded village elders made a poignant appearance at a memorial service last month for an Army staff sergeant killed by one of those devices.

Those indications of progress are among a mosaic of developments that point to a profound shift across a swath of Afghanistan that has been the focus of the American-led military campaign: For the first time since the war began nearly a decade ago, the Taliban is commencing a summer fighting season with less control and influence of territory in the south than it had the previous year.

“We start this year in a very different place from last year,” Gen. David H. Petraeus, the top coalition commander in Afghanistan, said in a recent interview.

The security improvements have been the result of intense fighting and the use of high-impact weapons systems not normally associated with the protect-the-population counterinsurgency mission.

In Sangin, Zhari and Arghandab — the three most insurgent-ridden districts in the south — the cost in American lives and limbs since the summer has been far greater than in any other part of the country. More than 40 Marines have been killed in Sangin in the past nine months, and three dozen more have lost both legs. The Army brigade responsible for Zhari and part of Arghandab has lost 63 soldiers since July.

The question of the moment for Petraeus and his subordinates is whether the gains will hold as Taliban commanders, laden with cash and munitions, stream across the desert from Pakistan, where there has been considerably less progress in denying them sanctuary.

Senior U.S. officers said they expect the insurgents to shift tactics: Instead of trying to take on American troops directly, as they did in Sangin and Zhari in the fall, the Taliban will attempt to plant more homemade explosives, recruit a new cadre of suicide bombers and assassinate Afghan government officials — as it did late last week, killing the police chief in Kandahar province. The result, according to an internal military projection, could be a far more violent summer for both Americans and Afghans.

Petraeus and other U.S. commanders say they are hopeful that Afghan civilians will feel confident enough to report Taliban activity to U.S. or Afghan troops. They also are optimistic that improvements in the quality of the Afghan army and of U.S. battlefield intelligence will provide a significant boost to counterinsurgency efforts.

For now, however, President Obama, who has pledged to begin pulling out troops in July, faces a complex and risky challenge. Within the next three months, he must decide whether the tenuous but promising changes in southern Afghanistan merit a significant reduction of forces or a more token drawdown.

That calculus also will be complicated by a deterioration of security in eastern Afghanistan. Because senior officers had long assumed the east was more secure than the south, the bulk of the surge forces were sent southward to Helmand and Kandahar provinces. Now some of those officers are hoping to shift more troops east if the improvements in the south hold.

Petraeus has not provided his withdrawal recommendation to Obama. The four-star general said the progress across southern Afghanistan remains “fragile and reversible,” although he also has made it clear to his subordinates that he thinks it can be cemented with enough time and military pressure.

Other U.S. military officials and some diplomats regard the transformation as unsustainable. They doubt Afghan government officials, police officers and soldiers will be able to take control of cleared areas by 2014, the year by which the United States and its NATO allies have pledged to cede responsibility for security to the Afghans.

“It’s great that the Taliban has been pushed out of these areas, but then what?” said a senior U.S. official involved in Afghanistan policy who was not authorized to speak on the record. “Once we leave these places, it’s hard to imagine that the Afghans will really be able to hold on to them.”

Officers across southern Afghanistan say the changes that have taken place during the fall and winter — the result of a gloves-off pummeling of insurgent strongholds, deals with tribal elders and changes in local government — have increased the chances that this shift might be different from so many earlier proclaimed successes. And even if the Taliban makes some gains, military officials maintain that the destruction of numerous insurgent bunkers, the seizure of tons of munitions and the removal of thousands of homemade bombs will put the group at an unprecedented disadvantage this summer.

Intercepted Taliban communications suggest insurgent commanders are increasingly demoralized, according to military intelligence officers. In Kandahar province, levels of Taliban activity were lower this March than a year ago, the officers said.

“We’ve changed the battlefield,” said Lt. Col. Jason Morris, commander of the 3rd Battalion of the 5th Marine Regiment. His unit took 29 fatalities during its seven-month deployment in Sangin, more than any other battalion in Afghanistan. “They’re not going to be able to fight the way they used to.”

The killing fields

For the Marines in 3/5’s Kilo Company, their very first patrol led them into the horrors of Sangin.

On the afternoon of Oct. 14, 1st Platoon exited its new home, a spartan outpost in a belt of farmland between the Helmand River and Route 611, the district’s main north-south road. Walking single file, scanning the shoulder-high cornfields for signs of insurgents, the platoon set out for a nearby village.

The Marines had not traveled more than 250 yards when the shooting started. First a few pops. Then a volley. And then a fusillade from not just AK-47 rifles but belt-fed machine guns as well.

Pinned down amid the corn, the platoon radioed for help. A reinforced machine-gun squad from 2nd Platoon threw on its gear and left the outpost to set up a blocking position so the Marines from 1st could withdraw. But as soon as the backup squad neared the scene, it was ambushed by a dozen insurgents.

Within minutes, the squad’s leader was shot in the leg. The only place his comrades could take cover was an adobe compound to the southwest marked on their maps as Building 3.

It was then that those Marines — and soon the rest of Kilo Company — would come to understand why Sangin had become the killing fields of the war in Afghanistan.

As the squad rushed toward the compound, one of the machine gunners stepped on a homemade mine on the southern corner. He was blown into a nearby canal.

On the north side of the building, a Marine seeking cover behind a wall was struck by a bomb planted in it. When the squad’s medic rushed over to help him, he stepped on a pressure-triggered makeshift bomb. He lost both his legs, and the Marine he sought to save died before the medevac helicopters arrived.

There were so many explosions, so close together, that others in the platoon assumed fellow Marines were firing mortar rounds at the Taliban. Only later would they understand that the sound was from their buddies stepping on mine after mine.

“It opened our eyes,” said Sgt. Joel Bailey, a machine gunner in the squad who jumped into the canal and tried unsuccessfully to save the first Marine felled by the explosions. “It was then that we realized that it was going to be a slugfest for a while.”

By the time 1st Platoon and the response squad from 2nd Platoon made it back to their outpost, they discovered another challenge. They were desperate for more ammunition, but the Taliban had dammed up nearby irrigation canals, flooding the sole dirt road leading to the outpost and rendering it impassable to armored U.S. vehicles. The Marines eventually were forced to wade through the muck on foot, hoisting the ammunition on combat stretchers, under the cover of darkness.

“This was Day One,” said Capt. Nikolai Johnson, the commander of Kilo Company.

The rest of the year would prove to be just as arduous and bloody. Johnson and his troops learned that, like Building 3, canal embankments and tree lines that seemed like natural points of defense throughout Sangin were lined with mines by the Taliban.

By the end of December, Taliban attacks had claimed the lives of eight men from Johnson’s company of about 120 Marines. Two dozen more were injured so severely that they had to be sent home, several as double or triple amputees.

But Johnson’s company refused to hunker down in its posts. Almost every day, the Marines would set out on another mission, often in the direction of buildings flying white Taliban flags, even if it meant stepping on a mine. Their goal was to get in fights and kill as many insurgents as they could.

“We developed a hunter mentality,” he said. “This was a great place to be if you’re a Marine infantryman.”

Flattening a village

When Lt. Col. David Flynn brought his 800-strong battalion from the Army’s 101st Airborne Division to northern Arghandab in July, he expected to wage the sort of counterinsurgency mission that has become vogue in the U.S. military. He would win over the locals by building schools and clinics, providing agricultural assistance, and sipping tea in weekly shuras with village elders.

But as soon as his soldiers arrived, they faced the same reception as the Marines in Sangin. Mines fashioned from plastic jugs of homemade explosive and crude, pressure-sensitive triggers were everywhere — on dirt paths, under culverts, in the branches of pomegranate trees.

Sometimes the bomb-sniffing dogs caught them. Sometimes the soldiers spotted them. And sometimes they stepped on them. Blown-off limbs quickly became the signature injury for America’s surge troops in the south.

In the battalion’s first 100 days on the ground, it lost seven soldiers. Another 70 were wounded.

So instead of sipping tea, Flynn decided to strike back.

An initial target was the village of Tarok Kolache, a collection of about a dozen mud-brick, multi-family housing compounds surrounded by pomegranate orchards. Video from surveillance aircraft indicated that the village had been vacated, save for insurgents who were manufacturing homemade explosives in the walled-off courtyards.

“The place was completely riddled with evil,” he said.

Officers in Flynn’s battalion had the aircraft fly overhead for a few weeks to ensure there were no signs of civilians who had returned. He also consulted a local leader who confirmed that all the residents had left Tarok Kolache.

Then he requested and received permission to flatten the village.

U.S. B-1B Lancer and A-10 Warthog jets conducted repeated bombing runs. A new ground-launched artillery rocket system also pelted the enclave. All told, almost 25 tons of ordnance was dropped on Tarok Kolache.

When it was over, the village was a giant patch of dirt, save for a few mud walls that survived the onslaught.

Flynn described the bombed-out village as “a parking lot.” But he insisted he did not bomb a village. “We bombed an enemy stronghold,” he said.

His unit went on to flatten parts of three other nearby villages.

Such aggressive measures, far harder-edged than how the U.S. military has traditionally operated in Afghanistan, became a critical component of operations across the south. In Zhari, soldiers fired more than 400 high-explosive line charges — small rockets that pull a wire embedded with C4 and can clear a truck-wide path for 110 yards. Everything in the way was pulverized, including roadside bombs, crops and homes.

In Sangin, the Marines used 24 line charges to tear up a 1,600-yard stretch of road embedded with 52 bombs. In another part of the district, they used multiple charges to demolish tall compound walls that insurgent snipers employed for concealment; Marine officers have told residents that if they want to rebuild, their walls must be lower than four feet.

The Army has changed the landscape in even more unusual ways in Zhari. Soldiers have sought to block off the western side of the district by building a five-mile-long sand berm topped with razor wire. Taking a page out of the military’s Iraq playbook, they also have installed more than 10 miles of tall concrete walls along roads in the southern half of the district that cut through flat farmland. While some residents find the sight of cement walls running alongside wheat fields to be overly penal, the unsightly measures are aimed at restricting insurgents’ ability to drive back into the area with munitions-filled vehicles.

The tactics have not fueled a groundswell of anger, in large part because the destroyed compounds were largely empty and no civilians were killed. The military also has been doling out compensation, in the form of cash payments or, in the case of Tarok Kolache, a U.S.-supervised rebuilding of a village.

Flynn’s battalion established an outpost in the village and hired contractors to resurrect the structures. The local mosque, once a mud-walled edifice, has been rebuilt with brick and concrete; it features colorful minarets and a large prayer room. Laborers are working on a series of long brick buildings to replace the adobe housing compounds.

Flynn also is planning a change to the tall mud walls that Afghans typically use to mark their property. Instead of establishing a height requirement, he has purchased rolls of chain-link fencing. He is hoping to persuade the Afghans to give it a try.

Residents appear generally supportive of Flynn’s effort, in part because they are getting a construction upgrade and payments for three years of lost crops. The cost of the overall reconstruction effort in Tarok Kolache, including compensation for damaged fields and culverts, is about $1.3 million. Flynn regards it as a small price to pay to evict the Taliban and save the lives and limbs of his soldiers.

Since the village was razed, Flynn said, there has been almost no insurgent activity in the area. The presence of U.S. troops has made it an inhospitable place to reestablish bomb factories. Residents also are expressing a greater willingness to provide information about Taliban infiltration.

Flynn thinks they are motivated by a new sense of security — as well as a new deterrent in the form of Tarok Kolache’s destruction.

“People understand that if the Taliban come back again, that could happen again,” he said.

Getting a new leader

Nothing seemed to be breaking Col. Art Kandarian’s way in Zhari this past summer.

The Taliban had mined the dirt paths through the district’s agricultural belt, forcing his troops to scale row after row of chest-high mud mounds farmers use to grow grapes. It reminded him of the hedgerows in Normandy that so challenged the American soldiers in the weeks after D-Day.

The Afghan army battalion assigned to fight alongside his soldiers was fresh out of basic training and had no combat experience. Only one of the 500 soldiers was from Kandahar province. The rest had no local knowledge.

But perhaps the most vexing problem was the local government in Zhari. It consisted of one man, Karim Jan, the district governor. And Kandarian’s soldiers quickly learned that the official was not much of a leader.

He rarely left the district’s main town, and he had little interest in convening assemblies of village elders. He steered jobs and resources to his fellow Alizai tribesmen, and he seemed beholden to the local power broker, Haji Lala.

The Americans wanted Karim Jan out, but there was little they thought they could do about it. His presence in the district was the direct result of political deals made by President Hamid Karzai.

Then Kandarian finally got lucky. When American officials learned that Karim Jan was trying to spring two men from police custody who were implicated in the deaths of three U.S. soldiers, they pounced. The pressure led the governor of Kandahar province to move Karim Jan to another district and anoint a well-regarded Zhari resident as the new district leader.

The change in leadership, Kandarian said, has been “instrumental in Zhari’s transformation.”

The new district governor, Niaz Mohammad Sarhadi, has built a staff of two dozen municipal employees, including education and agriculture officials. He convenes regular community meetings and travels through the district. And he has been persuading Zhari residents who fled to Kandahar city to return to their homes.

The impact has been profound. On a recent Friday morning, Kandarian’s deputy, Lt. Col. Joseph Krebs, headed to a village three miles south of his base for a gathering of elders. The trip there took 15 minutes — and not a shot was fired. This past fall, soldiers would have been pelted with gunfire and rocket-propelled grenades within minutes of moving south from the base.

When he arrived at a combat outpost near the village, Krebs walked about in awe.

“Just being able to stand here is amazing,” he said. “Six months ago, if you were here, you were in a gunfight.”

At the meeting, held in an Army tent, 45 elders sat in a circle, munching on apples provided by the soldiers. Much of the session was devoted to complaints — the lack of a doctor, the poor flow of water in irrigation canals, the need for a new school.

Krebs and his fellow officers deemed the meeting a success. The fact that residents were willing to gather, even if to complain, was a major step forward.

Before the participants left, Lt. Col. Ghulam Hazrat, the Afghan army battalion commander in the area, implored them to seize the opportunity afforded by the American-led push to evict the Taliban over the past several months. He urged them to stand up to the insurgency by reporting any suspicious behavior, and he told them to take advantage of U.S.-funded day-labor programs.

Hazrat did not delve into the politics of the war playing out in Washington, but it was clear he understood the slim prospects of the U.S. military expending so much blood and treasure over another year if residents again acquiesced to the Taliban.

“This is a golden chance,” he said. “You’ll never get it again.”

Cutting a peace deal

Leaders of the Alikozai tribe in the upper Sangin valley had spent a year talking to Afghan government officials about a peace deal.

But the discussions never progressed beyond preliminaries. The Alikozai were scarred by a previous attempt to oppose the Taliban, in 2007, that collapsed when they failed to receive assistance from Afghan and coalition forces. The Taliban tied one Alikozai elder to the back of a pickup truck and dragged him out of the district.

There also was the problem of Alikozai involvement in large-scale opium processing in the valley. The tribe did not seem ready to give up its hand in the lucrative drug trade.

Then, in the fall, an elite Marine reconnaissance battalion pushed into the Alikozai area, about five miles north of where Kilo Company was operating. The unit’s initial mission was to secure Route 611. Opening that road through Sangin, and north to the Kajaki Dam, is a critical priority for U.S. commanders because they want to repair the dam’s hydropower generators.

But the recon Marines also served as a cudgel. They were attacked by young Alikozai fighters who had been egged on and paid off by Taliban commanders. So the Marines fought back. In October and November, the reconnaissance battalion killed about 200 Alikozai militants in the valley. The 3rd Battalion of the 5th Marine Regiment, the unit in Sangin that suffered devastating casualties, killed several hundred more insurgents to the south over the same period, many of them Alikozai as well.

“We started stacking bodies like cordwood,” said an officer in Sangin, who like other Marines asked for anonymity to speak frankly. “And they came to a point where they said, ‘Holy [expletive], there aren’t that many of us left.’ ”

On New Year’s Day, Alikozai elders agreed to a security pact with the governor of Helmand province that calls for the tribe to forsake the Taliban and rein in its young men from joining the insurgency. In exchange, the Afghan, U.S. and British governments will fund development projects in the 15-mile-long Alikozai area and the Marines will consider releasing some Alikozai detainees.

Afghan officials and U.S. diplomats hailed the deal as a sign of how the promise of reconstruction aid can lead to reintegration, but Marine officers have a different view of why the Alikozai came to the table.

“You can’t just convince them through projects and goodwill,” another Marine officer said. “You have to show up at their door with two companies of Marines and start killing people. That’s how you start convincing them.”

Since the deal was struck, violence has dropped significantly in the valley. But the real test will occur later this spring, after the vast tracts of opium-producing poppies are harvested in Sangin. Will the Alikozai remain good to their word? And will the tribe be able to fend off an expected onslaught by Taliban commanders eager to recruit young men to reclaim territory they lost to the Marines last fall?

“Do they have the will and the capacity?” said Morris, the commander of the 3/5. “It remains to be seen.”

Marines and Afghan officials now are trying to replicate the Alikozai deal with other tribes in the area. On a recent morning, Morris and the governor of Sangin, Mohammed Sharif, traveled to southern Sangin to meet with men from the Ishakzai tribe, a historically marginalized group that has been embraced by the Taliban.

Standing under camouflage netting on a dusty Marine base, the gray-bearded Sharif, a former schoolteacher, implored 50 men seated before him to renounce the insurgency.

“Dear brothers, it’s enough,” he said. “The things you have done, it’s enough. Come back to the government. If you have done bad deeds, God will forgive you.”

But none of the Ishakzai expressed any interest in reconciling. Many in the tribe continue to grow poppies on their land and fear a deal with the government would interfere with their livelihoods.

After brief speeches from the police chief and Morris, the elders got up to leave. As they departed, several thrust claims for property damage at the governor and the Marines.

“The people are still scared,” a one-legged, white-turbaned elder named Abdul Haq said as he hobbled away. “If we unite, the Taliban will come to each of our homes and kill us.”