Right up until he was assassinated, Hassan Nasrallah did not believe that Israel would kill him.

As he hunkered inside a Hezbollah fortress 40 feet underground on Sept. 27, his aides urged him to go to a safer location. Mr. Nasrallah brushed it off, according to intelligence collected by Israel and shared later with Western allies. In his view, Israel had no interest in a full-scale war.

What he did not realize was that Israeli spy agencies were tracking his every movement — and had been doing so for years.

Not long after, Israeli F-15 jets dropped thousands of pounds of explosives, obliterating the bunker in a blast that buried Mr. Nasrallah and other top Hezbollah commanders. The next day, Mr. Nasrallah’s body was found in an embrace with a top Iranian general based in Lebanon. Both men died of suffocation, the intelligence found, according to several people with knowledge of it.

The death of Hezbollah’s feared leader, who for decades commanded a Lebanese militia in its fight against the Israeli state, was the culmination of a two-week offensive. The campaign combined covert technological wizardry with brute military force, including remotely detonating explosives hidden in thousands of pagers and walkie-talkies used by Hezbollah, as well as a withering aerial bombardment with the aim of destroying thousands of missiles and rockets capable of hitting Israel.

It was also the result of two decades of methodical intelligence work in preparation for an all-out war that many expected would eventually come. A New York Times investigation, based on interviews with more than two dozen current and former Israeli, American and European officials who spoke on the condition of anonymity to discuss classified operations, reveals just how extensively Israeli spies had penetrated Hezbollah. They recruited people to plant listening devices in Hezbollah bunkers, tracked meetings between one top commander and his four mistresses, and had near constant visibility into the movements of the militia group’s leaders.

It is a story of breakthroughs, as in 2012 when Israel’s Unit 8200 — the country’s equivalent of the National Security Agency — stole a trove of information, including specifics of the leaders’ secret hide-outs and the group’s arsenal of missiles and rockets.

There were stumbles, as in late 2023 when a Hezbollah technician got suspicious about the batteries in the walkie-talkies.

And there were scrambles to save their efforts, as in September, when Unit 8200 collected intelligence that Hezbollah operatives were concerned enough about the pagers that they were sending some of them to Iran for inspection.

Worried that the operation would be exposed, top intelligence officials persuaded Prime Minister Benjamin Netanyahu of Israel to give the order to detonate them, setting in motion the campaign that culminated in the assassination of Mr. Nasrallah.

Israel’s decimation of Hezbollah was a significant victory for a country that, one year earlier, had suffered the greatest intelligence failure in its history, when Hamas-led fighters invaded it on Oct. 7, 2023, killed more than 1,200 people and took 250 hostages.

The Hezbollah campaign, part of a broader war that has killed thousands of people in Lebanon and displaced more than a million, defanged one of Israel’s greatest adversaries and dealt a blow to Iran’s regional strategy of arming and funding paramilitary groups bent on Israel’s destruction. The weakening of the Iran-led axis reshaped the dynamics in the Middle East, contributing to the fall of the Assad regime in Syria.

The contrast between Israel’s approaches to Hezbollah and to Hamas is also stark and devastating. The intense intelligence focus on Hezbollah shows that the country’s leaders believed that the Lebanese militia group posed the greatest imminent threat to Israel. And yet it was Hamas in the Gaza Strip, a group Israeli intelligence believed had neither the interest nor the abilities to attack Israel, that launched a surprise attack and caught the nation unprepared.

Israel was in a standoff with Mr. Nasrallah and his top commanders of Hezbollah, the “Party of God,” for decades, and Israeli intelligence assessments have concluded that it will take years, possibly more than a decade, for the group to rebuild after their deaths. The group of leaders now in charge has far less combat experience than the earlier generation.

And yet the new leaders, like Hezbollah’s founders, are driven by a central animating principle: conflict with Israel.

“Hezbollah can’t continue to get support and funding from Iran without being in a war against Israel. That’s the raison d’être for Hezbollah,” said Brig. Gen. Shimon Shapira, a former military secretary for Mr. Netanyahu and the author of “Hezbollah: Between Iran and Lebanon.”

“They will rearm and rebuild,” he said. “It’s only a matter of time.”

Building a Network of Sources

The 2006 war between Israel and Hezbollah was a bloody stalemate. Israel withdrew from Lebanon after 34 days of fighting, which began after Hezbollah kidnapped and killed two Israeli soldiers. The war, which did not achieve Israel’s objectives, had been something of a humiliation, forcing an investigation panel, resignations of top generals and a reckoning inside Israel’s security apparatus about the quality of its intelligence.

But operations during the war, based on Israeli intelligence gathering, formed the foundation for the country’s later approach. One operation planted tracking devices on Hezbollah’s Fajr missiles that gave Israel information about munitions hidden inside secret military bases, civilian storage facilities and private homes, according to three former Israeli officials. In the 2006 war, the Israeli Air Force bombed the sites, destroying the missiles.

In the years after the war, Mr. Nasrallah projected confidence that Hezbollah could win another conflict against Israel, likening the nation to a spider web — menacing from afar but a threat that could be easily brushed aside.

As Hezbollah rebuilt, the Mossad, Israel’s foreign intelligence service, expanded a network of human sources inside the militia, according to 10 current and former American and Israeli officials.

Specifically, the Mossad recruited people in Lebanon to help Hezbollah build secret facilities after the war. The Mossad sources fed the Israelis information about the locations of hide-outs and assisted in monitoring them, two officials said.

The Israelis generally shared Hezbollah intelligence with the United States and European allies.

A significant moment came in 2012, when Unit 8200 obtained a trove of information about the specific whereabouts of Hezbollah leaders, their hide-outs and the group’s batteries of missiles and rockets, according to five current and former Israeli defense and European officials.

That operation raised confidence within Israeli intelligence agencies that — should Mr. Netanyahu make good on threats to attack Iran’s nuclear sites — the Israeli military could help neuter Hezbollah’s ability to retaliate.

Mr. Netanyahu visited the Tel Aviv headquarters of Unit 8200 shortly after the operation. During the visit, the head of Unit 8200 made a show by printing out the trove of information, producing a tall stack of paper. Standing next to the material, he told Mr. Netanyahu, “You can now attack Iran,” according to two current and former Israeli defense officials with knowledge of the meeting.

Israel did not attack.

During the years that followed, Israeli spy agencies worked to refine the intelligence gathered from the earlier operation to produce information that could be used in the event of a war with Hezbollah.

According to two Israeli defense officials with knowledge of the intelligence, when the 2006 war ended, Israel had “target portfolios” for just under 200 Hezbollah leaders, operatives, weapons caches and missile locations. By the time Israel launched its campaign in September, it was tens of thousands.

Turning Pagers Into Deadly Devices

To gain an advantage in an eventual war with Hezbollah, Israel also developed plans to sabotage the militia from within. Israel’s Unit 8200 and Mossad championed a plan to supply Hezbollah with booby-trapped devices that could be detonated at a future date, according to six current and former Israeli defense officials.

Within the Israeli intelligence community, the devices were known as “buttons” that could be activated at Israel’s moment of choosing.

Designing and producing the buttons was relatively straightforward. Israeli engineers mastered placing PETN explosives within the batteries of electronic devices, turning them into small bombs.

The more difficult operation fell to the Mossad, which for nearly a decade tricked the group into buying military equipment and telecommunication devices from Israeli shell companies.

In 2014, Israel seized an opportunity when the Japanese technology company iCOM stopped producing its popular IC-V82 walkie-talkies. The devices, originally assembled in Osaka, Japan, were so popular that replicas were already being made across Asia and sold in online forums and in black market deals.

Unit 8200 discovered that Hezbollah was specifically searching for the same device to equip all of its frontline forces, according to seven Israeli and European officials. They had even designed a special vest for their troops with a chest pocket tailored for the device.

Israel began manufacturing its own replicas of the walkie-talkies with small modifications, including packing explosive material into their batteries, according to eight current and former Israeli and American officials. The first Israeli-made replicas arrived in Lebanon in 2015 — and more than 15,000 were eventually shipped, some of the officials said.

In 2018, a female Israeli Mossad intelligence officer drafted a plan that would use a similar technique to implant explosive material into a pager battery. Israeli intelligence commanders reviewed the plan, but determined that Hezbollah’s use of pagers was not widespread enough, according to three officials. The plan was shelved.

Over the next three years, Israel’s increasing ability to hack into cellphones left Hezbollah, Iran and their allies increasingly wary of using smartphones. Israeli officers from Unit 8200 helped fuel the fear, using bots on social media to push Arabic-language news reports on Israel’s ability to hack into phones, according to two officers in the agency.

Worried about smartphones being compromised, Hezbollah’s leadership decided to expand its use of pagers. Such devices allowed them to send out messages to fighters but did not reveal location data nor have cameras and microphones that could be hacked.

As it did, Hezbollah began looking for pagers hardy enough for combat conditions, according to eight current and former Israeli officials. Israeli intelligence officers reconsidered the pager operation, and worked to build a network of shell companies to hide their origins and sell the products to the militia.

Israeli intelligence officers targeted the Taiwanese brand Gold Apollo, well known for pagers.

In May 2022, a company called BAC Consulting was registered in Budapest. One month later, in Sofia, Bulgaria, a company called Norta Global Ltd. was registered to a Norwegian citizen named Rinson Jose.

BAC Consulting bought a licensing agreement from Gold Apollo to manufacture a new pager model known as the AR-924 Rugged. It was bulkier than the existing Gold Apollo pagers, but it was promoted as waterproof and with a longer-lasting battery life than competitors’ devices.

The Mossad oversaw production of the pagers in Israel, according to Israeli officials. Working through intermediaries, Mossad agents began marketing the pagers to Hezbollah buyers and offered a discounted price for a bulk purchase.

The Mossad presented the gadget, one without any hidden explosives, to Mr. Netanyahu during a meeting in March 2023, according to two people with knowledge of the meeting. The prime minister was skeptical about their durability, and asked David Barnea, the Mossad chief, how easily they might break. Mr. Barnea assured him they were sturdy.

Not convinced, Mr. Netanyahu abruptly stood up and threw the device against the wall of his office. The wall cracked, but the pager did not.

The Mossad front company shipped the first batch of pagers to Hezbollah that fall.

Conducting War Games

The pager operation was not fully in place in October 2023, when the Hamas-led attacks ignited a fierce debate within the Israeli government about whether Israel should launch a full-scale war against Hezbollah.

Some, including Defense Minister Yoav Gallant, argued for striking at Hezbollah, which began launching missiles at Israel on Oct. 8 in solidarity with Hamas. It was an opportunity, he said, to deal with the “hard enemy” of Hezbollah before turning to what he considered the less difficult enemy of Hamas, according to five Israeli officials familiar with the meetings.

After a phone call with President Biden on Oct. 11, 2023, Mr. Netanyahu, along with his newly formed war cabinet, decided for the time being against opening another front with Hezbollah, effectively ending high-level debate about the topic for months.

Even as Israel focused on Hamas, military and intelligence officials continued to refine plans for an eventual war with Hezbollah.

Israeli intelligence analysts, who were constantly monitoring the use of the devices, discovered a potential problem with the operation. At least one Hezbollah technician began to suspect that the walkie-talkies might contain hidden explosives, according to three Israeli defense officials. Israel dealt with it swiftly this year, killing the technician with an airstrike.

For nearly a year, Israeli intelligence and the air force also ran roughly 40 war games built around killing Mr. Nasrallah and other senior Hezbollah leaders, said two Israeli officials. They wanted to be able to target them at the same time, even if they were not in the same place.

Along the way, Israel collected mundane and intimate details about Hezbollah commanders, including the identities of the four mistresses of Fuad Shukr, a founding member of Hezbollah long ago identified by the U.S. government as one of the planners of the 1983 bombing of the barracks in Beirut, Lebanon, that killed 241 American Marines.

At one point this year, apparently feeling uncomfortable about his situation, Mr. Shukr sought assistance from Hezbollah’s highest religious cleric to marry all four women, according to two Israeli officials and a European official. The cleric, Hashem Safieddine, arranged four separate phone-based wedding ceremonies for Mr. Shukr.

The simmering conflict boiled over this summer, when a Hezbollah rocket attack in July killed a dozen Israelis, including schoolchildren, in Majdal Shams, a town in the Golan Heights.

Israel responded days later with an airstrike in Beirut that killed Mr. Shukr. It was a provocative step to take, to assassinate a top commander of Hezbollah’s forces.

‘Use It or Lose It’

After the back-and-forth attacks, the debate renewed inside Israel’s government about opening a “northern front” against Hezbollah. The Israeli military and the Mossad drew up different strategies for a campaign against Hezbollah, according to four Israeli officials.

In late August, Mr. Barnea, the Mossad chief, wrote a secret letter to Mr. Netanyahu, according to a senior Israeli defense official. The letter advocated a two-to-three-week campaign that included eliminating more than half of the group’s missile abilities and destroying installations within about six miles of the Israeli border. At the same time, senior military officials began their own effort to lobby Mr. Netanyahu to intensify a campaign against Hezbollah.

New intelligence disrupted the planning. Hezbollah operatives had become suspicious that the pagers might be sabotaged, according to several officials.

On Sept. 11, intelligence showed that Hezbollah was sending some of the pagers to Iran for examination, and Israeli officials knew it was only a matter of time before the covert operation would be blown.

On Sept. 16, Mr. Netanyahu met with top security chiefs to weigh whether to detonate the pagers in a “use it or lose it” operation, according to four Israeli security officials. Some opposed it, saying it might prompt a full Hezbollah counterattack and possibly a strike by Iran.

Mr. Netanyahu ordered the operation. The following day, at 3:30 p.m. local time, the Mossad ordered an encrypted message to be sent to thousands of the pagers. Seconds later, the pagers detonated.

At the time the pagers exploded, Mr. Jose, the Norwegian who was the head of one of the Mossad front companies, was attending a technology conference in Boston.

Within days, Mr. Jose was identified in news articles as a participant in the operation, and the Norwegian government announced that it wanted him back in Norway for questioning.

Israeli officials secretly pressured the Biden administration to ensure that Mr. Jose could leave the United States without going back to Norway, according to one Israeli and one American official.

Israeli officials would not disclose Mr. Jose’s location. One senior Israeli defense official said only that he was in a “safe place.”

Approving an Assassination

After the pager operation, the Netanyahu government, with the support of high-ranking defense officials, opted for all-out war, a campaign marked by a series of escalations.

The day after detonating the pagers, the Mossad blew up the walkie-talkies, most of which were still in storage because Hezbollah leaders had not yet mobilized fighters for a battle against Israel.

In all, dozens of people were killed by the pager and walkie-talkie explosions, including several children, and thousands were wounded. Most of the casualties were Hezbollah operatives, sowing chaos among the top ranks of the group.

Days after, on Sept. 20, Israeli jets struck a building in Beirut where commanders of Hezbollah’s elite Radwan Force were meeting in a bunker, killing several of them along with Ibrahim Aqeel, the head of Hezbollah’s military operations.

On Sept. 23, the Israeli Air Force conducted a major campaign, hitting more than 2,000 targets aimed at Hezbollah’s stores of medium and long-range missiles.

The most consequential decision remained: whether or not to kill Mr. Nasrallah.

As senior Israeli officials debated, intelligence agencies received new information that Mr. Nasrallah planned to move to a different bunker, one that would be far more difficult to hit, according to two Israeli defense officials and a Western official.

On Sept. 26, with Mr. Netanyahu set to fly to New York for a meeting of the United Nations General Assembly, the prime minister gathered with his top political, intelligence and military advisers to discuss approving the assassination. They also had to decide whether to tell the Americans in advance.

Mr. Netanyahu and other top advisers opposed notifying the Biden administration. They believed that U.S. officials would push back against the strike, but that regardless, the United States would come to Israel’s defense in case Iran retaliated.

They agreed to keep the Americans in the dark.

Mr. Netanyahu approved the assassination the next day, after he landed in New York and only hours before standing at the podium at the United Nations.

In his speech, he spoke about the grip that Hezbollah had over Lebanon. “Don’t let Nasrallah drag Lebanon into the abyss,” he told the presidents and prime ministers gathered.

Soon after, the Israeli F-15 jets above Beirut dropped thousands of pounds of explosives.

Adam Goldman contributed reporting from Washington.

The leader of Azerbaijan directly blamed Russia on Sunday for the crash of an Azerbaijan Airlines passenger jet last week, calling on Moscow to accept responsibility and offer compensation to victims.

President Ilham Aliyev said in an interview with Azerbaijan’s national broadcaster that a vague apology issued by President Vladimir V. Putin of Russia a day earlier would not suffice to preserve friendly relations between the two former Soviet states.

The Embraer 190 airliner was traveling from Baku, Azerbaijan, to Grozny in southern Russia on Wednesday, but was diverted from its path after encountering interference with its navigation systems and impact with external objects, according to Azerbaijan’s government. The plane crashed in Kazakhstan soon after, resulting in the deaths of 38 of the 67 people on board, more than half of them Azerbaijani citizens.

Azerbaijani and U.S. officials, as well as international aviation experts, had said they believed that the plane was most likely shot down by a Russian air defense missile. Moscow, however, has not admitted responsibility.

Mr. Aliyev’s comments on Sunday offered the most direct rebuke yet of Kremlin’s position on the crash.

“We can clearly say today that the plane was shot down by Russia,” Mr. Aliyev said in the interview, according to a summary published in English by Azerbaijan’s state news agency. “First, the Russian side must apologize to Azerbaijan. Second, it must acknowledge its guilt. Third, those responsible must be punished.”

Mr. Aliyev added that Moscow had met only the first condition thus far.

On Saturday, Mr. Putin broke the Kremlin’s three-day silence on the crash. He called Mr. Aliyev and apologized, without directly acknowledging Russian responsibility, according to summaries of the call published by the two governments.

“Vladimir Putin offered his apologies that the tragic incident took place in the Russian airspace,” the Kremlin said in its summary.

Russia said that as the plane approached Grozny, Russian air defenses had begun to repulse an attack by Ukrainian drones on the airport there and others nearby.

Ukraine, which has targeted Grozny with drones in recent weeks, has not confirmed or denied that such an attack took place.

Mr. Aliyev said in the television interview that the airliner was hit by accident. He criticized, however, Moscow’s tardy and noncommittal response, which initially attempted to blame the crash on fog or birds.

“Unfortunately, for the first three days, we heard nothing from Russia except for some absurd theories,” Mr. Aliyev said.

Analysts said that Mr. Aliyev had taken a strong stand on Russia because he himself accepted responsibility and offered compensation when Azerbaijan’s military mistakenly shot down a Russian military helicopter in 2020, killing two Russian service members.

“Azerbaijan now expects similar actions from Moscow,” said Zaur Shiriyev, a Baku-based foreign policy expert at the Carnegie Endowment for International Peace, a policy research organization.

It remains unclear if Mr. Aliyev’s strongly worded demands to the Kremlin signaled a cooling of relations between the two countries, or were meant primarily to satisfy a domestic audience.

Azerbaijan has assumed a neutral position on the war in Ukraine, benefiting from growing trade with Russia while exploiting Moscow’s distraction to pursue its interests in the Caucasus. Analysts have said the country has little incentive to let the crash derail this beneficial status quo with Moscow.

Some analysts have said that Mr. Putin could resolve the flare-up of tensions with Mr. Aliyev, a fellow autocrat with longstanding ties to Moscow elites, by striking a private deal.

Such a scenario would spare Mr. Putin the political cost of assuming responsibility for the crash but it would be likely to breed long-term resentment against Russia among the Azerbaijani public, the analysts say.

The Kremlin did not immediately comment on Mr. Aliyev’s demands on Sunday.

Milana Mazaeva contributed reporting from Istanbul.

Yi-Pin Lin, an associate professor at Tufts University, proudly says he has vacationed in 120 nations over the past decade.

But there was one country he had always dreamed of visiting, only to be frightened off by decades of war, kidnappings and terrorism: Afghanistan.

With the end of the Afghan war in 2021, the country’s new Taliban rulers began encouraging tourists to visit. So last month, Mr. Lin packed his bags, paid $130 for a visa and boarded a flight to Kabul, the Afghan capital.

“When I told my friends where I was going, they all thought I was crazy,” he said. “They said it was too dangerous.”

Mr. Lin, 43, is part of a small but growing vanguard of venturesome tourists making their way to Afghanistan, disregarding dire warnings issued by their governments. The State Department advises Americans not to travel to Afghanistan “due to terrorism, risk of wrongful detention, civil unrest, kidnapping and crime.”

Over the past three years, Taliban officials say, 14,500 foreign tourists have visited the isolated, poverty-stricken nation. They have arrived with hard currency that Afghanistan desperately needs.

Many tourists have experienced the country’s traditional hospitality while visiting its famous mosques, its towering mountain ranges, its scenic high deserts and the remains of the renowned Buddha statues in Bamiyan.

In the minds of many around the world, Afghanistan has conjured another image since the Taliban takeover: something akin to a prison. The country has become notorious for its suffocating restrictions on women, which have essentially erased them from public life.

The Taliban’s rise to power, however, has also brought a relative calm to the country with the end of the 20-year war.

Terrorist attacks continue to challenge the Taliban administration, including one this month by the Islamic State affiliate in Afghanistan that killed a high-ranking official. But the suicide bombings and roadside explosions that inflicted mass death during the war — mostly carried out by the Taliban themselves — have all but ceased.

The government has assured tourists that Afghanistan is safe, scenic, welcoming — and a bargain to boot.

“Ninety-five percent of tourists have a negative idea about Afghanistan because of incorrect media information and propaganda worldwide,” said Khobaib Ghofran, the spokesman for the Ministry of Information and Culture in Kabul.

When tourists visit the country, he said, they “see it is completely normal. When they get home, they share their photos and the positive information they found in Afghanistan.”

Taliban officials said they relied on tourists, especially bloggers and YouTubers, to extol the virtues of visiting Afghanistan. The Taliban government promotes tourism on its official websites and on social media, and Afghanistan’s 3,000 tourism agencies advertise overseas, they said.

Despite painful memories among Afghans of U.S. aerial bombings and night raids, American tourists are as welcome as anyone else, Mr. Ghofran said.

He said that guards were provided for tourists who requested security, but that visitors were not required to be accompanied by government escorts, as in North Korea.

However, foreign businessmen and journalists — and many Afghans — are routinely monitored by agents of the General Directorate of Intelligence.

A small percentage of foreign visitors are women, tourism officials said. Both Mr. Ghofran and Mawlavi Ahmadullah Muttaqi, the information and culture director for Herat Province, said there were no written strictures governing how female tourists should dress and behave in public.

“They can see for themselves our culture here,” Mr. Muttaqi said, adding that female visitors should respect it by wearing long, concealing garments and covering their hair with a head scarf. They are not required to wear burqas or cover their faces, according to Mr. Muttaqi and Mr. Ghofran.

The distinctions between Afghan women and female tourists can be startling.

“I know women are treated bad in Afghanistan, but as a woman, I see that everyone acts very nice to me,” said Marino Sakata, 23, a tourist from Japan who was traveling alone in Kabul and said she planned to return next year.

Ms. Sakata wore loosefitting slacks, yellow sneakers and a black coat whose hood covered her hair and part of her face — a fashion choice that drew sharp glances from some Afghans on the capital’s streets. She said she was considering buying a head scarf to better adhere to Afghan customs.

Pausing in conversation, she held up her smartphone to show a message through Google Translate: “Being a foreigner, I find it difficult that people stare at me.”

Male tourists, too, are expected to dress modestly, but they do not face the same intense scrutiny as women.

Greg Ernest, 67, a retired British consultant who visited Afghanistan for nine days last month, said the Afghan guide he hired told him to wear a shalwar kameez, the traditional clothes worn by Afghan men.

Mr. Ernest, who said he had visited every country in the world except Afghanistan before reaching Kabul, explained that he had been concerned about his safety when he arrived.

“I was slightly worried as a Brit,” he said, citing Britain’s prominent military role in the U.S.-led coalition. “But I was surprised at how well I was received. People were very hospitable.”

Tourists have visited from China, Russia, Ireland, Poland, Canada, Taiwan, Germany, France, Pakistan, Estonia, Sweden and elsewhere, tourism officials said. Travelers typically get their visa en route to Afghanistan, often at the Taliban-run consulates in Dubai or Peshawar, Pakistan.

Many venture to Bamiyan Province, west of Kabul, to see the remnants of the Buddha statues. Most tour the area uneventfully, but in May, three Spanish tourists and one Afghan were killed in the province. It was the first deadly attack on foreign tourists since the Taliban regained power.

Carved from sandstone cliffs more than 1,600 years ago, the two Buddhas once stood 125 and 175 feet tall. They were demolished in early 2001 by the Taliban under a campaign to destroy all “idolatrous” depictions of human figures.

Today, the Buddhas remain an awkward subject for the Taliban government. Asked about the Buddhas, Hurmatullah Fazli, the acting tourism director in Bamiyan, replied, “Next question.”

Jin, a Chinese tourist who asked that his surname not be published, said the Buddhas held deep emotional resonance for many Chinese, who represent the world’s largest population of Buddhists, at 244 million.

He said he had dreamed for years of visiting the statues — and “then my heart was broken” when they were destroyed.

Jin fought back tears as he stood amid the rubble of the Buddhas last month. “This place is sacred to us,” he said.

The Taliban’s destruction of archaeological artifacts and ancient artworks at the National Museum of Afghanistan in Kabul in early 2001 is also a sensitive topic. The museum is popular with foreign tourists, along with the nearby Gardens of Babur.

Allen Ruppel, 63, a retired insurance company executive from Wisconsin, visited both sites last month. He said he had been apprehensive about visiting Afghanistan, concerned that an American might encounter resentment or worse.

When he told his wife where he was going, he said, she joked that “I can’t stop you, but I might get an Afghan hound to replace you.”

Mr. Ruppel, who wore a blue shalwar kameez, said he was surprised by how warmly he had been received by Afghans and by how safe the country seemed.

He said he would encourage his friends to “open your minds and take a fresh look at Afghanistan.”

Many tourists seem spellbound by the spectacular Afghan landscape and its wealth of historical and archaeological sites. The Silk Road crossed Afghanistan, creating a crossroads of cultures rich in history and artifacts.

Hiking a trail next to the deep-blue waters of mountain lakes in Band-e-Amir national park in central Afghanistan, beneath soaring peaks crusted with brilliant white snow, Professor Lin was relaxed and exuberant.

“I’ve never felt unsafe here,” he said. “That’s what has most surprised me. I have to say it’s been an exotic experience.”

Yaqoob Akbary, Safiullah Padshah and Elise Blanchard contributed reporting.

We had just walked into the fentanyl lab when the cook poured a white powder into a stockpot full of liquid. He began mixing it with an immersion blender and fumes rose from the pot, filling the small kitchen.

We wore gas masks and hazmat suits, but the cook had on only a surgical mask. He and his partner had rushed here to fulfill an order for 10 kilograms of fentanyl. While one sniff of the toxic chemicals could kill us, they explained, they had built up a tolerance to the lethal drug.

But then, the cook jerked back.

“It really hit me,” he said, looking dazed. “I need to take a breather.”

The young man rushed out of the room.

In September, a war broke out within Mexico’s Sinaloa cartel. Fighting between the rival factions has terrorized the northwestern state of Sinaloa in the months since, leaving hundreds dead and causing a billion dollars in economic damage, business leaders say. The Mexican government responded by sending in a swarm of soldiers and making a slew of arrests.

After President-elect Donald J. Trump threatened tariffs if the country didn’t stop drugs from crossing the border, Mexico’s security forces announced their largest seizure of fentanyl ever this month: 20 million doses of the drug.

Criminal groups have had to adjust to the new conditions on the ground. Fearing law enforcement raids or attacks by their rivals, they say they’re moving their labs around more often than usual and producing drugs in new locations.

And yet, even in the middle of all-out war and intense government pressure, Mexico’s cartels are still doing a swift business. In the last five years, illicit fentanyl, a synthetic opioid, became the leading cause of death for young adults in the United States.

We — two New York Times reporters and one photographer — had been trying for months to get access to a fentanyl lab run by the Sinaloa cartel, which the U.S. government says is responsible for much of the product flooding into the United States. But every time we thought we were getting close, some unforeseen outburst of violence derailed our plans.

When we came to the capital city of Culiacán in September, a van appeared on the side of a road with at least five bodies inside. No one at the scene knew which faction of the cartel the men had belonged to or who had killed them. That night, we heard shots right outside our hotel — the discovery of the bodies had apparently prompted gun battles between the rival groups. It was too unsafe to get into the lab.

The second try was scuttled because of clashes between security forces and cartel gunmen; the third because of an incursion by one group that left several houses burned out. We saw a demonstration of fentanyl being made in a cartel safe house but could not get into the location where the cooks produced larger batches.

Then, on our fourth try, we finally got in.

The lab was hidden in a house right in the city center in Culiacán, on a bustling street full of pedestrians, cars and food stands. There were no smells or fumes outside that would have alerted a passer-by to the large quantities of fentanyl being cooked behind the door.

It was dark inside save for a room at the very back, which lit up in bright red flames as soon as we arrived. Two men hustled to put out the fire coming from a pot on the stove, surrounded by smoke that had a reddish tint.

After a few minutes, they emerged triumphant and apologetic: A chemical reaction had caused a small explosion, explained the main cook, a 26-year-old wearing a navy shirt and slacks.

We gained access thanks to one of our contacts, who knew a drug trafficker who did business with the cooks. The contact convinced the men that we would not reveal their identities or the lab’s location. The men said they risked deadly reprisals by talking to reporters, and spoke on the condition of anonymity.

The main cook and his partner shook our hands. Their boss, a middle-aged man hovering nearby, allowed us to take one phone and one camera inside. They warned us to be ready for law enforcement to appear at any moment.

“They busted in on us this morning,” the boss said. Earlier that day, he explained, the Mexican military had raided one of his crew’s labs, which forced them to bring their material to this makeshift site.

“If they bust in here, you can stay, but hit the floor,” the main cook told us. “We’re running.”

After putting on gas masks, hazmat suits and gloves, we went into the kitchen.

On a round side table near the doorway, illuminated by a fluorescent lamp, was a pile of white powder that the men told us was finished fentanyl. It looked to be more than a pound — most likely enough for more than 200,000 doses.

The countertop was dotted with half-empty Corona bottles and metal containers with chemicals. On one tray lay a small mountain of crystal flakes that the main cook said was sodium hydroxide, a fentanyl ingredient.

The men were leaning over two large saucepans sitting on burners that had been set to medium low. They said they were at the first stage of the process, activating the main chemical ingredient they use to make fentanyl. There was one small window and a plastic floor fan for ventilation.

Normally, the cooks wear gas masks while making fentanyl, to protect against toxic exposure to chemicals. But in their scramble to restart the process after the military raid, they had time only to find cloth or surgical masks, they said. That’s why the main cook’s partner had to run out of the room when fumes started permeating the air.

He came back, cigarette in hand, and handed the main cook acetone, another chemical ingredient for fentanyl that was sitting in the kitchen pantry next to a bottle of hot sauce. On a wall nearby hung a print of Leonardo da Vinci’s “Last Supper.”

The main cook had started working for the cartel at 16, he said, cooking methamphetamine and later fentanyl. While teaching himself how to run a drug lab, he stayed in school, studying oral medicine. The would-be dentist never took up the trade.

In the years since fentanyl took off in the United States, he said, he has made millions of dollars running several drug labs. Two U.S. Embassy officials who monitor fentanyl production said these earnings were expected for someone at the main cook’s level in the criminal organization.

He said he bought himself sports cars, houses and ranches. His crew acquired a helicopter and a small plane, he said. He blamed Americans for the overdose epidemic, saying that users were the ones deciding to take such a lethal drug. He snorted in disbelief when asked whether pressure from the United States or his own Mexican government would put an end to the fentanyl industrial complex.

“This is what makes us rich,” he said. “Drug trafficking is the main economy here.”

Putting on gloves, he dipped his hand into a bucket full of fentanyl powder and began to massage in blue dye. He was mixing in the colorant, he said, because this material would soon be pressed into pills and eventually sold to American users.

His crew takes orders from cartel traffickers in Mexico, who then package the goods and send them across the border. He has the equipment to stamp each tablet with whatever design the client wants, showing us a pill with a crown in the style of the Rolex insignia.

He expertly worked his fingers through the bucket of now-neon blue drugs, breaking up clumps that had the consistency of pastry dough. The cook compared it with making flour tortillas.

Then his partner appeared at the doorway and signaled to him, with a throat-slitting gesture, to shut the kitchen down. Members of the crew had received information from a lookout that a Mexican military patrol was too close, and they needed to move.

“We have to go,” said the main cook, turning off the stove and heading for the exit. “We have to run.”

After peeling off our protective gear and grabbing our phones, we ran out of the house, too.

Meridith Kohut contributed reporting.

A passenger plane carrying 181 people crash-landed on its belly on Sunday at an airport in South Korea, hitting a barrier and exploding into an orange fireball in the worst aviation disaster in the country in almost three decades.

Nearly all of the people on board the plane, a Boeing 737-800 operated by Jeju Air, were killed, officials said.

The plane, Flight 7C2216, had taken off from Bangkok and was landing at Muan International Airport in South Korea’s southwest when it crashed around 9 a.m. local time. Officials said the plane had broken into so many pieces that only its tail was identifiable.

The plane was carrying 175 passengers and six crew members. As of Sunday evening, the official death toll had risen to 179, according to the National Fire Agency. Only two people — crew members who were rescued from the aircraft’s tail section — survived.

What caused the crash?

Officials were investigating why the landing gear appeared to have malfunctioned, and whether birds had struck the plane or if bad weather had been a factor, Ju Jong-wan, a director of aviation policy at the Ministry of Land, Infrastructure and Transport, said at a news briefing.

As the plane was landing, he said, the airport warned it about a potential bird strike. The plane issued a mayday alert shortly after, he said, then crash-landed.

The muddy tidal flats near Muan International Airport and much of the west coast of the Korean Peninsula are favorite resting places for migrant birds. Photographs in local media showed flocks of birds flying near the airport​ on Sunday.

Footage broadcast by MBC-TV showed one of the engines briefly emitting flames as it neared the airport.

Kim E-bae, the chief executive of Jeju Air, said at a news conference that the plane had no history of accidents, and also had no problems during routine maintenance checks.

The plane’s landing gear appeared not to have dropped down from underneath, and the flaps on its wings apparently were not activated for landing, said Keith Tonkin, the managing director of Aviation Projects, an aviation consulting company in Brisbane, Australia, who reviewed video of the crash.

“The aircraft was essentially in a flying configuration,” he said. That meant the plane was most likely “flying faster than it would normally be in a landing situation.”

Crashes are often caused by multiple factors, which can take years to uncover through in-depth investigations.

This was South Korea’s worst passenger plane crash in decades.

Sunday’s crash was the worst aviation accident involving a South Korean airline since a Korean Air jet slammed into a hill in Guam, a U.S. territory in the western Pacific, in 1997. That crash killed 229 of the 254 people onboard.

It also appeared to have been the first fatal crash for Jeju Air, a low-cost South Korean carrier that was established in 2005 and flies to dozens of countries in Asia.

Two days earlier, the plane involved in the crash had been flying to Beijing from Jeju, a Korean island south of the mainland, when it had to divert to Seoul, according to the flight tracking site Flightradar24. The diversion was caused by a medical, not technical, emergency onboard, according to the Incheon International Airport Police Corps.

After that, the plane flew 10 flights between South Korea, Malaysia, Japan, China, Taiwan and Thailand without incident, according to Flightradar24, before Sunday morning’s crash.

In 2021, the South Korean authorities investigated Jeju Air after one of its planes flew despite having a defect, according to reports in the domestic news media. A tip of one of its wings was damaged during a landing, but the crew failed to notice the damage and the plane took off again, The Korea Herald reported.

Last year, the airline received a safety grade of A, or “very good,” from the South Korean Ministry of Land, Infrastructure and Transport’s annual review of domestic airlines. The score is based on the number of accidents or near accidents. The highest grade any airline got that year was A++, and the lowest was B+.

The Boeing 737-800 has a strong safety record.

The Jeju Air plane that crashed was a Boeing 737-800, a model that is used widely around the world and is a staple of low-cost airlines. There are about 4,400 Boeing 737-800s in service globally, according to Cirium, an aviation data provider. That’s about 15 percent of the passenger planes operating globally.

“The plane in question is very safe and has a good safety record,” said Najmedin Meshkati, a professor of engineering at the University of Southern California who has studied the safety history of the Boeing 737 line.

It was possible that the plane’s landing gear did not deploy because of a “maintenance” problem, he said, though he said he would not rule out a bird strike as a cause.

Mr. Meshkati said that the Boeing 737-800’s landing gear was well designed and had a history of reliability.