ALINGAR, Afghanistan — Under the shade of a mulberry tree, near grave sites dotted with Taliban flags, a top insurgent military leader in eastern Afghanistan acknowledged that the group had suffered devastating losses from American strikes and government operations over the past decade.

But those losses have changed little on the ground: The Taliban keep replacing their dead and wounded and delivering brutal violence.

“We see this fight as worship,” said Mawlawi Mohammed Qais, the head of the Taliban’s military commission in Laghman Province, as dozens of his fighters waited nearby on a hillside. “So if a brother is killed, the second brother won’t disappoint God’s wish — he’ll step into the brother’s shoes.”

The Taliban have outlasted a superpower through nearly 19 years of grinding war. And dozens of interviews with Taliban officials and fighters in three countries, as well as with Afghan and Western officials, illuminated the melding of old and new approaches and generations that helped them do it.

After 2001, the Taliban reorganized as a decentralized network of fighters and low-level commanders empowered to recruit and find resources locally while the senior leadership remained sheltered in neighboring Pakistan.

The insurgency came to embrace a system of terrorism planning and attacks that kept the Afghan government under withering pressure, and to expand an illicit funding engine built on crime and drugs despite its roots in austere Islamic ideology.

At the same time, the Taliban have officially changed little of their harsh founding ideology as they prepare to start direct talks about power-sharing with the Afghan government.

They have never explicitly renounced their past of harboring international terrorists, nor the oppressive practices toward women and minorities that defined their term in power in the 1990s. And the insurgents remain deeply opposed to the vast majority of the Western-supported changes in the country over the past two decades.

“We prefer the agreement to be fully implemented so we can have an all-encompassing peace,” Amir Khan Mutaqi, the chief of staff to the Taliban’s supreme leader, said in a rare interview in Doha, Qatar’s capital, with The New York Times. “But we also can’t just sit here when the prisons are filled with our people, when the system of government is the same Western system, and the Taliban should just go sit at home.”

“No logic accepts that — that everything stays the same after all this sacrifice,” he said, adding, “The current government stands on foreign money, foreign weapons, on foreign funding.”

A grim history looms. The last time an occupying power left Afghanistan — when the U.S.-backed mujahedeen insurgency helped push the Soviets to withdraw in 1989 — guerrillas toppled the remaining government and then fought each other over its remains, with the Taliban coming out on top.

Now, even as United States forces and the insurgents have stopped attacking each other, the Taliban intensified their assaults against the Afghan forces before a rare three-day truce this week for the Eid holiday. Their tactics appear aimed at striking fear.

Many Afghans fear the insurgents will bully negotiators into giving them a dominant stake in the government — whose institutions they have undermined and whose officials they continue to kill with truck bombs and ambushes.

Taliban field commanders made clear that they were holding fire only on American troops to give them safe passage — “so they dust off their buttocks and depart,” as one senior Taliban commander in the south said. But there was no reserve about continuing to attack the Afghan Security Forces.

“Our fight started before America — against corruption. The corrupt begged America to come because they couldn’t fight,” a young commander of the Taliban elite “Red Unit” in Alingar said. He was a toddler when the United States invasion began, and met up with a Times reporting team in the area where government control gives way to the Taliban.

“Until an Islamic system is established,” said the commander, who spoke on the condition of anonymity, “our jihad will continue until doomsday.”

Recruiting and Control

The Taliban now have somewhere between 50,000 and 60,000 active fighters and tens of thousands of part-time armed men and facilitators, according to Afghan and American estimates.

It is not, however, a monolithic organization. The insurgency’s leadership built a war machine out of disparate and far-flung parts, and pushed each cell to try to be locally self-sufficient. In areas they control, or at least influence, the Taliban also try to administer some services and resolve disputes, continuously positioning themselves as a shadow government.

“This is a network insurgency — it’s very decentralized, it has the ability for the commanders at the district level to mobilize resources, and be able to logistically prepare,” said Timor Sharan, an Afghan researcher and former senior government official. “But at the top, they gained legitimacy from a single source, a single leader.”

Over the years, the group’s top leadership has mostly remained in Pakistan, where the insurgency’s reconstitution was supported by Inter-Services Intelligence, the Pakistani military spy agency. Those havens have offered continuity even as the rank and file suffer heavy casualties in Afghanistan.

At times, the casualty rates went so high — losing up to hundreds of fighters a week as the Americans carried out an airstrike campaign in which they dropped nearly 27,000 bombs since 2013 — that the Taliban developed a system of reserve forces to keep applying pressure where it had taken losses, according to the group’s regional commanders. Last year was particularly devastating, with Afghan officials claiming they were killing Taliban at unprecedented rates: more than 1,000 a month, perhaps a quarter of their estimated forces by year’s end. In addition to airstrikes by Afghan forces, the U.S. dropped about 7,400 bombs, perhaps the most in a decade.

Even at the peak of the long American military presence and the coordinating effort to help the Afghan government win hearts and minds in the countryside, the Taliban were able to keep recruiting enough young men to keep fighting. Families keep answering the Taliban’s call, and booming profits help hold it all together.

Mawlawi Qais explained how his military commission in Laghman Province, where Alingar is, has an active “Guidance and Invite” committee whose members go to mosques and Quranic lessons to recruit new fighters. But he noted that most recruits come from current fighters working to enlist friends and relatives.

There has been a constant need for new blood, particularly over the past decade. “In our immediate dilgai alone,” he said, referring to a unit of 100 to 150 fighters, “we have lost 80 men.”

Still, fighters keep signing up, he said, in part because of deep loathing for the Western institutions and values the Afghan government has taken up from its allies.

“Our problem isn’t with their flesh and bones,” Mawlawi Qais said. “It is with the system.”

Afghan officials say that in places where the Taliban don’t have stable control for local recruitment, they still draw heavily on the approximately two million Afghan refugees who live in Pakistan, and on the seminaries there, to recruit fighters for front-line fighting.

Taliban recruitment officials and commanders say they don’t pay regular salaries. Instead, they cover the expenses of the fighters. What has helped in recent years was giving their commanders a freer hand in how they used their local resources — and war booty.

Some revenue collection, such as taxing goods, was centralized. But increasingly, the movement became deeply intertwined with local crime and narcotics concerns, adding to the financial incentives to keep up their holy war.

“The friends who are with us in the front lines of jihad, they don’t get exact salaries,” said Mullah Baaqi Zarawar, a unit commander in Helmand Province. “But we take care of their pocket money, the gas for their motorcycle, their trip expenses. And if they capture spoils, that is their earning.”

In areas where they are comfortably in control, many Taliban fighters, and even the leaders, keep other jobs.

During his interview, Mawlawi Qais paused to apologize for his dusty clothes — he said he had been milling flour all morning, which is his day job. Many of his fighters also have second jobs when not fighting.

To help ensure that recruitment streams would not dry up, the insurgency prioritized an increasingly sophisticated information operation, shaping the Taliban’s narrative through slick video productions and an aggressive social media brigade.

Instances of U.S. or Afghan forces causing civilian casualties, whether real cases or made up, are splashed across social media in conjunction with Taliban training videos of their fighters jumping through fiery rings and drilling with their weapons. The message has been consistent: To join us is to take up a life of heroism and sacrifice.

They had powerful symbols to draw on: They were fighting for a supreme leader, Mawlawi Haibatullah Akhundzada, who sent his own son as a suicide bomber for the cause, against a government propped up by an invading military and led by officials who often keep their families abroad.

After their deal with the Americans, the Taliban’s propaganda has only intensified, and has taken on an ominously triumphal note. In his annual message for the Eid al-Fitr holiday, released last Wednesday, the Taliban’s supreme leader issued a promise of amnesty for enemies who renounced their loyalty to the Afghan government.

Alingar is also an example of how the Taliban have figured out local arrangements to act like a shadow government in areas where they have established control. The insurgents collect taxes, sending around 20 percent to the central leadership while keeping the rest for the fighters locally, Taliban leaders in the district said. They have committees overseeing basic services to the public, including health, education and running local bazaars.

Supplies and salaries for health clinics and schools are still paid for by the Afghan government and its international donors. But the Taliban administer it all in their way — a compromise reluctantly agreed to by aid organizations since the alternative would be no services. And the insurgents’ approach to schooling is giving the strongest evidence yet that the movement is clinging to its old ways of repressing women, art and culture.

Out of the 57 schools in Alingar, 17 are girls schools, according to Mawlawi Ahmadi Haqmal, the head of the education committee in Alingar. But the local Taliban insist that girls’ education must end after sixth grade, at odds with international requirements for education aid. In the curriculum, the Taliban have also slashed culture as a subject because it promoted “vulgarities such as music,” Mawlawi Haqmal said.

Born of Anarchy

After the Taliban swept to power in the 1990s, defeating other factions in the vacuum left behind by the Soviet withdrawal, the United States seemed mostly indifferent to the group’s oppressive rule. But that changed in 2001, when Al Qaeda leaders taking shelter in Afghanistan carried out the Sept. 11 terrorist attacks on American soil.

Al Qaeda’s Saudi leader, Osama bin Laden, had spent a long time in Afghanistan, and once even fought on the American side against the Soviets at the end of the Cold War. The Taliban’s leader, Mullah Muhammad Omar, allowed him to stay in Afghanistan and the two had grown close, with Bin Laden pledging allegiance to him as an Islamic emir.

Wounded and seeking immediate revenge, the Bush administration had no patience for the Taliban’s proposals to find a way to get rid of Bin Laden without directly handing him to the Americans. The United States began a military invasion.

A group that had found success against Afghan factions withered quickly in the face of the U.S. airstrikes. The Taliban’s fighters went home as the Islamic Emirate disintegrated. Their leaders crossed the border into Pakistan or ended up in American prisons.

Many Taliban commanders interviewed for this article said that in the initial months after the invasion, they could scarcely even dream of a day they might be able to fight off the U.S. military. But that changed once their leadership regrouped in safe havens provided by Pakistan’s military — even as the Pakistanis were receiving hundreds of millions of dollars in American aid.

From that safety, the Taliban planned a longer war of attrition against U.S. and NATO troops. Starting with more serious territorial assaults in 2007, the insurgents revived and refined an old blueprint the United States had funded against the Soviets in the same mountains and terrain — but now it was deployed against the American military.

“Most of our leaders were part of that anti-Soviet war. This was our land, our territory, and our colleagues had familiarity,” said Mr. Mutaqi, the Taliban chief of staff. “Afghanistan’s history was in front of us — when the British came, their force was bigger than the Afghans, when the Soviets came, their force was bigger, and the same was true with the Americans — their force was much larger than ours. So that gave us hope that, eventually, the Americans, too, would leave.”

From the start, the insurgents seized on the corruption and abuses of the Afghan government put in place by the United States, and cast themselves as arbiters of justice and Afghan tradition — a powerful part of their continued appeal with many rural Afghans in particular. With the United States mostly distracted with the war in Iraq, the insurgency widened its ambitions and territory.

By the time President Barack Obama took office in 2009, the Taliban had spread so far that he raised the number of American troops on the ground to about 100,000. In addition to an Afghan Army and police that eventually grew to about 300,000 fighters, the U.S. military also propped up local Afghan militias as urgent measures. The war had entered a vicious cycle of killing and being killed.

Violent Heights

In the second decade of the insurgency, the Taliban have been defined by the ruthlessness of their violence — and by their ability to strike at will even in the most guarded parts of the Afghan capital, Kabul.

The Taliban revived the old fund-raising networks in Arab states that had helped finance the U.S.-supported mujahedeen movement against the Soviets.

A prime example of how the Taliban took old guerrilla experiences to new brutality was the development of the Haqqani network and its integration into the leadership.

The network’s patriarch, Jalaluddin Haqqani, was seen as an effective and cooperative American ally in the fight against the Soviets. But in the war against the Americans, the Haqqanis ended up as the only arm of the Taliban to be designated by the United States as a foreign terrorist group.

The Haqqanis turned their old smuggling routes and networks into a pipeline for suicide bombers and well-trained fighters who struck American targets and assaulted critical Afghan government agencies.

Jalaluddin’s son, Sirajuddin, was promoted to be the Taliban’s deputy leader and a senior operations commander in 2015. The younger Mr. Haqqani — originally from eastern Afghanistan — often sent his elite trainers to embed with Taliban units in the insurgency’s southern heartland, Afghan and Western officials said, cranking up the lethality of their violence.

When the United States began negotiating in 2018 with a delegation of the Taliban in Doha, across the table were architects of the insurgency — and the survivors of it. Nearly half of the Taliban negotiating delegation had spent a decade each in Guantánamo.

Mullah Abdul Ghani Baradar, the lead Taliban negotiator, had just been released after 10 years in Pakistani prison, detained because he had made contacts for peace talks with the Afghan government without the blessing of the Pakistani military establishment that had nurtured the insurgency.

Each session, Mullah Baradar would arrive at the venue of talks, a posh diplomatic club, in a pair of black Chevrolet Impala sedans. Half a dozen guards in white robes would rush between the American-made vehicles and the gate, one holding open the car door, ushering the frail, turbaned leader up the stairs into the marble hall where the Americans were impatient to end the war.

As the two sides talked, car bombs rammed into military bases back in Afghanistan, and Taliban suicide squads continued attacking government offices, often causing mass civilian casualties. Several times the violence complicated or even derailed the delicate talks.

One main concern among American and Afghan officials was whether the Taliban’s political wing and the likes of Mullah Baradar had true influence among the insurgency’s military commanders.

Another question was whether the Taliban would truly turn against terrorist groups like the Islamic State and Al Qaeda once the Americans left.

During one session last spring, the commander of U.S. and NATO forces, Gen. Austin S. Miller, appealed to the Taliban to find common cause with the American counterterrorism mission.

“Our guys could continue killing each other,” he said, “or we could kill ISIS together.”

American officials say that President Trump’s negative view of the talks improved dramatically when the Taliban began delivering on that front. The insurgents intensified pressure on the Islamic State foothold in the east just as the United States bombed them from the sky and Afghan commandos squeezed from another direction.

Still, when it came to Al Qaeda, the group walked a fine line in the agreement with the United States — refusing the descriptor of “terrorist,” a word that bogged down the negotiations for several emotional days. The Taliban showed no remorse for its past cooperation with Al Qaeda, promising only to not allow Afghan soil be used for launching attacks in the future.

About two weeks after the Taliban signed their deal with the United States, Al Qaeda in a statement hailed it as a “great victory” against America.

Corralling the Lower Ranks

The Taliban demonstrated their ability to control their ranks through one more test. When the two sides conditioned the signing of their agreement on a week of partial truce, violence levels dropped by as much as 80 percent, Afghan and American officials said.

That had not been a sure thing. Mullah Baradar steadfastly refused to make the seven days a complete cease-fire — a move that many Afghan and Western observers believe gave the Taliban leadership some space to not lose face in case any rogue cells disobeyed the order to stop fighting.

There were other signs that Mullah Baradar was having to keep up a sophisticated juggling act behind the scenes. Some Afghan officials said they had intelligence that Mullah Baradar had issued an ultimatum to the Taliban’s military wing, saying that if it insisted on trying to win by force, there was no need for him to keep spending his days arguing with the Americans word by word, comma by comma.

When the week of violence reduction began, Taliban commanders were scrambling — on WhatsApp groups and on military radio channels — to bring their fighters and units into line. Victory is close and this is what the leadership wants and we need to deliver, they would tell their fighters, according to intelligence intercepts shared with The New York Times by Afghan officials.

One thing that slowed down the negotiations with the United States was that the Taliban’s political leaders wanted to take every small issue down to their commanders, bringing them on board to avoid rebellions and breakaways.

For weeks, the turbaned negotiators would sit across from the Americans in conference rooms in Doha and then send delegations back to Pakistan, for consultations with the leadership.

In between, there was always WhatsApp. When the insurgent negotiators took punctual breaks from talks for prayer, they would pick up their phones from the locker box on the way. The incoming messages beeped throughout the prayer in the mosque, and the scrolling would begin as soon as hands touched the face in culmination of worship.

Taliban officials say what sets them apart from the factions that fought against the Soviet Union and then broke into anarchy over power is that their allegiance was divided to more than a dozen leaders. The Taliban began their insurgency under the authority of a single emir, Mullah Omar. But the insurgency reached its greatest heights more recently, with a leadership structure that depends on consensus and then strikes with a heavy fist against any who disobey from within.

Even as new commanders emerged in recent years, much of the leadership council is made up of the older crew that established the insurgency in the years after the U.S. invasion. The old political leaders acknowledge the balancing act they face is like no challenge the insurgency has faced before. They have made sure to tightly control the rationale for their violence — it is a holy war for as long as their supreme leader and clerics decree it to be.

Mr. Sharan, the analyst, said that unity has been easier to maintain with a common enemy, the U.S. military, to fight. But if the Taliban eventually win their dream of an Afghanistan without the Americans, he said, they will face many of the challenges that once dragged the country into anarchy.

“The relationship between the political leaders and the military commanders who have monopoly over resources and violence will be tested,” he said. “The 1990s civil war in Kabul happened not because the political leaders couldn’t agree among each other — it happened because the commanders who had monopoly of violence at the bottom wanted to expand on their resources. The political leaders were hopeless in controlling them.”

Taimoor Shah contributed reporting from Kandahar, and Zabihullah Ghazi from Jalalabad, Afghanistan.