Syria’s new president has spoken often about the urgency of merging the many armed groups that fought to topple the strongman Bashar al-Assad into a unified national army.

But the spasm of violence that erupted this month in northwestern Syria, which killed hundreds of civilians, made it clear just how distant that goal remains. It displayed instead the government’s lack of control over forces nominally under its command and its inability to police other armed groups, experts said.

The outburst began when insurgents linked to the ousted Assad dictatorship attacked government forces on March 6 at different sites across two coastal provinces that are the heartland of Syria’s Alawite minority. The government responded with a broad mobilization of its security forces, which other armed groups and armed civilians joined, according to witnesses, human rights groups and analysts who tracked the violence.

Groups of these fighters — some nominally under the government’s control and others outside of it — fanned out across Tartus and Latakia Provinces, killing suspected insurgents who oppose the new authorities, the rights groups said. But they also shelled residential neighborhoods, burned and looted homes and carried out sectarian-driven killings of Alawite civilians, according to the rights groups.

The leaders of the new government and the fighters now in its security forces are overwhelmingly from Syria’s Sunni Muslim majority, while the civilian victims of this wave of violence were overwhelmingly Alawites, a minority sect linked to Shiite Islam. The Assad family is Alawite, and during its five decades ruling Syria, it often prioritized members of the minority community in security and military jobs, meaning that many Sunnis associate the Alawites with the old regime and its brutal attacks on their communities during the country’s 13-year civil war.

It will take time for a clearer picture of the events to emerge, given their geographic spread, the number of fighters and victims involved and the difficulty of identifying them and their affiliations. But the violence on the coast represented the deadliest few days in Syria since Mr. al-Assad’s ouster in December, showcasing the chaos among the country’s armed groups.

The Syrian Network for Human Rights, a conflict monitor, said in a report last week that militias and foreign fighters affiliated with the new government, but not integrated into it, were primarily responsible for the sectarian and revenge-driven mass killings this month.

The government’s weak control over its forces and affiliated fighters and the failure of those forces to follow legal regulations were “major factors in the increasing scale of violations against civilians,” the report said. As the violence escalated, it added, “some of these operations quickly turned into large-scale acts of retaliation, accompanied by mass killings and looting carried out by undisciplined armed groups.”

On Saturday, the network raised the number of killings it had documented since March 6 to more than 1,000 people, many of them civilians. Another war monitoring group, the Syrian Observatory for Human Rights, on Friday put the overall death toll at 1,500, most of them Alawite civilians.

No direct evidence has surfaced linking the atrocities to senior officials in the new government, led by interim President Ahmed al-Shara. And the government said it had created a fact-finding commission to investigate the violence and vowed to hold anyone who committed abuses against civilians to account.

“Syria is a state of law,” Mr. al-Shara said in an interview with Reuters published last week. “The law will take its course on all.”

He accused insurgents linked to the Assad family and backed by an unnamed foreign power of setting off the violence but acknowledged that “many parties entered the Syrian coast, and many violations occurred.” He said the fighting became “an opportunity for revenge” after the long and bitter civil war.

During that war, which killed more than a half million people, according to most estimates, many rebel factions formed to fight Mr. al-Assad. Some of them allied with Mr. al-Shara’s Sunni Islamist rebel group in the final battle that ousted the dictator.

Then in late January, a group of rebel leaders appointed Mr. al-Shara president, and he has since vowed to dissolve the country’s many former rebel groups into a single national army. But he had been in office for little more than a month when the unrest in the coastal provinces erupted.

“The unity of arms and their monopoly by the state is not a luxury but a duty and an obligation,” Mr. al-Shara told hundreds of delegates at a recent national dialogue conference.

But he faces tremendous challenges in uniting Syria’s disparate rebel groups.

Many fought hard during the civil war to carve out fiefs that they are reluctant to give up. The conflict devastated Syria’s economy, and Mr. al-Shara inherited a bankrupt state with little money to build an army. And international economic sanctions imposed on the former regime remain in place, hobbling efforts to solicit foreign aid.

So the effort to integrate the armed groups has made little concrete progress.

“The unification is all fluff. It’s not real,” said Rahaf Aldoughli, an assistant professor at Lancaster University in England who studies Syria’s armed groups. “There is a weak command structure in place.”

At the core of the new security forces are former fighters from Hayat Tahrir al-Sham, the Sunni Islamist rebel faction that Mr. al-Shara led for years, experts said. They have a cohesive command structure that Mr. al-Shara oversees but lack the manpower needed to secure the entire country.

Large parts of Syria are still controlled by powerful factions not yet integrated into the national security forces, such as a Kurdish-led militia that dominates the northeast and Druse militias that hold sway in a region southeast of the capital, Damascus.

Other rebel groups allied with Mr. al-Shara have officially agreed to merge into the new, national force but have yet to actually do so. Most have received no training or salaries from the government and remain loyal to their own commanders, Dr. Aldoughli said.

Other armed groups also remain that have no connection to the government, as well as civilians who armed up to protect themselves during the war.

“There has not been much effort to improve the discipline or even the structures of those armed factions,” said Haid Haid, a consulting fellow who studies Syria at Chatham House, a London think tank. “What we have seen is an example of how fragmented and poorly trained those forces are.”

When the unrest erupted on March 6, fighters from many of these groups rushed to join in, with a variety of motives. Some wanted to put down the insurgency, while others sought revenge for violations committed during the civil war.

Much of the violence had a deeply sectarian cast.

In videos posted online, many fighters denigrated Alawites and framed attacks on them as retribution.

“This is revenge,” an unidentified man says in a video shared online that shows groups of fighters looting and burning homes believed to belong to Alawites. The video was verified by The New York Times.

In recent days, the government has announced the arrests of fighters seen committing violence against civilians in videos posted online. It was a positive step toward accountability, Mr. Haid said, but he wondered whether the government would track down and punish fighters whose crimes had not been caught on camera.

“It does not seem that the military forces have the internal mechanisms to identify who did what during those operations and take the appropriate measures,” he said.

The world’s youngest nation faces the threat of war yet again.

This month, a United Nations helicopter was attacked during an evacuation mission in a remote area in South Sudan, with one member of its crew killed and two others seriously injured. The flight was rescuing wounded government soldiers who had clashed with an armed group in Upper Nile State in the northeast. A day later, the United States said it was removing all nonemergency government employees from the country, citing security threats.

The attack underscored the shaky stability of the East African nation, almost a decade and a half after it gained independence amid hope and fanfare. The latest clashes, and the preceding political tensions, have regional observers fearing the collapse of a peace deal that was agreed on seven years ago.

Here’s what to know.

Who’s fighting?

The main parties involved in the latest clashes are the South Sudanese national military, under the government of President Salva Kiir, and an opposition force known as the White Army, which is believed to be allied with Vice President Riek Machar.

Mr. Kiir and Mr. Machar led the two warring sides of the civil war that broke out in 2013, ending with a fragile peace agreement in 2018. The deal demilitarized the capital, Juba, moved to ensure that both sides shared earnings from oil exports and returned Mr. Machar as vice president.

Yet deep-seated political and ethnic tensions have endured, as have militias and armed factions with shifting loyalties. Clashes are frequently characterized by interethnic violence, particularly between Mr. Kiir’s Dinka and Mr. Machar’s Nuer ethnic groups. Recurring violence has precipitated large-scale displacement, plunged the country into economic free-fall and sharply raised the price of food and fuel.

What led to the latest escalation?

Mr. Machar’s political coalition has accused the government of targeting his allies in February, including by launching a large-scale operation against his supporters in Upper Nile State. At least 22 political and military leaders allied with Mr. Machar have been arrested, with the whereabouts of some of them still unknown, Human Rights Watch has said.

In early March, the government accused the White Army of attacking and capturing a military garrison in the northern town of Nasir along the border with Ethiopia. The authorities in Juba responded by arresting several of Mr. Machar’s allies, including the deputy chief of the army, Gen. Gabriel Duop Lam, and the petroleum minister, Puot Kang Chol.

The U.N. helicopter in Upper Nile came under fire on March 7, despite assurances of safe passage, according to the chief of the U.N. South Sudan mission, Nicholas Haysom. In addition to a member of the helicopter crew, the attack left several military officers dead, including a general, the United Nations said.

The latest tensions have put the delicate government at risk of collapsing, with opposition groups describing the arrests as a sign of Mr. Kiir’s reluctance to honor the peace agreement and his determination to maintain control over the country’s political landscape. Presidential elections, now scheduled for next year, have repeatedly been delayed, causing frustration among opposition factions.

“South Sudan is one major escalation away from slipping into a new civil war,” said Alan Boswell, the Horn of Africa director at the International Crisis Group. “Should the government collapse or large-scale ethnic violence break out, the country could fragment.”

Have U.S. aid cuts affected the situation?

The cuts in American aid are already having a dire impact on the humanitarian situation in South Sudan. The United States spent $760 million on programs, including emergency food assistance and health, in the country in 2023.

Aid groups say the dearth of humanitarian aid is worsening food insecurity, and the cessation of health programs may spread diseases like cholera, malaria and tuberculosis even further. In January, the United Nations said that violence, bureaucratic impediments and cash extortion of its contractors were impeding effective delivery of aid, including in Upper Nile State.

What role does Uganda play?

Uganda said last week that its special forces had deployed to Juba to “secure” the South Sudanese capital. The Ugandan military chief said in a social media post that his nation recognized Mr. Kiir as the country’s only president.

“Any move against him is a declaration of war against Uganda,” he said, adding, “All those who commit that crime will learn what it means.”

Officials in Juba have not publicly confirmed the presence of the troops. But the Ugandan governing party’s parliamentary caucus endorsed the deployment, describing it as a “necessary intervention for peace enforcement to protect lives, restore stability and prevent further escalation of conflict.”

Uganda’s longtime president, Yoweri Museveni, has deployed troops to South Sudan several times in the past to prop up Mr. Kiir’s government. Yusuf Serunkuma, a researcher and scholar at Makerere University in Uganda, said that reports of a decline in Mr. Kiir’s health meant he needed Mr. Museveni’s backing even more. (South Sudan’s presidency has repeatedly denied assertions that Mr. Kiir has health problems.)

A civil war in neighboring Sudan that has killed tens of thousands and displaced many more has also disrupted South Sudan’s oil exports, limiting Mr. Kiir’s ability to fund his patronage network, observers say.

“Salva Kiir has accused Riek Machar of planning to overthrow him in a coup — an old accusation since the founding of the country,” Mr. Serunkuma said. But with the Ugandan deployment, he added, “They’ll probably sustain the status quo.”

Regional observers worry that the Ugandan deployment and an eventual state collapse could converge with the war to the north in Sudan and engulf the region in further conflict.

What happens next?

The United Nations and regional bodies have called on the South Sudanese leaders to de-escalate the crisis and resolve issues through dialogue. Leaders from the eight-nation Intergovernmental Authority on Development called last week for the release of detained officials “unless credible evidence warrants legal proceedings.”

The U.N. Commission on Human Rights in South Sudan also said that all parties should work to make the changes necessary to complete a transitional period ahead of elections, including by overhauling the Constitution.

The Kremlin said Monday that preparations were underway for a phone call between President Vladimir V. Putin and President Trump, as questions swirled over the American president’s comments suggesting that power plants and “dividing up” Ukrainian assets were on the agenda.

The highly anticipated phone call, scheduled for Tuesday, will be the first known conversation between the two leaders since Ukraine agreed to support a U.S.-backed monthlong cease-fire, as long as Russia does the same. While Mr. Trump has unequivocally stated his desire to broker some sort of truce as quickly as possible, Mr. Putin seems to be seeking to exploit the moment to win more concessions.

Speaking aboard Air Force One on Sunday evening, Mr. Trump said that he expected to discuss territorial issues with Mr. Putin as well as the fate of Ukrainian power plants. He also noted that there had already been discussions about “dividing up certain assets.”

“We want to see if we can bring that war to an end,” Mr. Trump said. “Maybe we can. Maybe we can’t, but I think we have a very good chance.”

The Kremlin’s spokesman confirmed on Monday that a call was expected to take place the following day but declined to disclose the conversation topics when asked whether Ukrainian power plants would be discussed.

“We never get ahead of things,” said the spokesman, Dmitri S. Peskov, since in Moscow’s “opinion the contents of conversations between the two leaders cannot be discussed a priori.”

Mr. Putin has not yet agreed to the 30-day cease-fire that U.S. officials proposed after talks with Ukrainian officials in Jeddah, Saudi Arabia. He has said the idea was “the right one and we definitely support it” — but laid out numerous conditions that could delay or derail any truce.

“There are questions that we need to discuss, and I think that we need to talk them through with our American colleagues and partners,” he told a news conference on Thursday.

Those remarks came just before Mr. Putin met with Steve Witkoff, who serves as Mr. Trump’s special envoy to the Middle East. But he has been involved in the peace talks over Ukraine and other discussions about restoring ties between Moscow and Washington.

Mr. Witkoff told CNN on Sunday that his meeting with Russia’s leader had lasted three to four hours. He declined to share the specifics of their conversation, but said it went well and that the two sides had “narrowed the differences between them.”

President Volodymyr Zelensky of Ukraine has accused Mr. Putin of stalling while Russia’s army advances on the battlefield to strengthen his hand in talks with the Trump administration about pausing the hostilities.

Moscow’s push to drive out Ukrainian troops from most of the Kursk region of Russia in recent days has deprived Kyiv of an important bargaining chip in any potential negotiations.

With its advance in Kursk, Russia can show Mr. Trump that it holds the momentum on the battlefield. Battlefield maps compiled by both Russian and Western groups analyzing combat footage and satellite images show that Russian forces have already crossed into Ukraine’s Sumy region from Kursk, in what analysts say may be an effort to flank and encircle the remaining Ukrainian troops in Kursk or open a new front in the war.

Mr. Zelensky has accused Russia to preparing to mount a larger offensive into the Sumy region, which is home to hundreds of thousands of people. Those actions, he said, indicated that Mr. Putin was not interested in peace.

Since the American proposal for a cease-fire, Mr. Zelensky said on Sunday night, “Russia stole almost another week — a week of war that only Russia wants.”

“We will do everything to further intensify diplomacy. We will do everything to make diplomacy effective,” he wrote on social media.

The reference to “power plants” by Mr. Trump was the latest indication that they might factor into any such diplomacy around a cease-fire. While the president did not elaborate, his comments came on the same day Mr. Witkoff mentioned a “nuclear reactor” in an interview with CBS News.

That appeared be a reference to the Zaporizhzhia nuclear plant in southern Ukraine, which Russia seized early in the war and still controls.

The six-reactor plant, Europe’s largest, has not supplied power to Ukraine’s grid since its capture. Its proximity to frontline fighting has long raised concerns about the risk of a radiological disaster.

Ukraine has repeatedly demanded Russian forces leave the power plant in order to reduce the risk of a nuclear accident and ease the country’s power shortages. But that possibility has grown increasingly unlikely as Russia strengthens its hold on occupied territories in Ukraine.

Viktoria Hryb, the head of the Ukrainian Parliament’s subcommittee on energy security, said she was “a little surprised that the question of the plant emerged” in the remarks by Mr. Trump and Mr. Witkoff.

“Ukraine wants it back,” she said, but it isn’t clear why Russia would give it up.

It was not immediately clear, though, whether any discussion about the power plant would focus on Russia giving it up — or finding a way to keep it under any truce.

The power plant sits near the Dnipro River in Ukraine’s southern Zaporizhzhia region, which Russia has officially annexed despite controlling only part of its territory.

Surrendering it would mean ceding territory Russia considers its own. It would also give Kyiv’s troops a foothold in a Russian-controlled area that has been relatively protected from Ukrainian attacks thanks to the natural barrier of the large Dnipro River.

At the same time, energy experts say, the nuclear plant is in poor condition after three years of war and restoring full operations would require a lot of time and investment from Russia. That could mean Russia might see an incentive to try to trade it for something else, such as the easing of Western sanctions on the Russian economy, experts say.

Victoria Voytsitska, a former lawmaker and senior member of the Ukrainian Parliament’s energy committee, noted that Moscow had long sought to resume oil and gas exports to Western countries. Those exports, a crucial source of revenue for Russia’s government, largely stopped after the war began, as European countries moved to wean themselves off Russian energy supplies and imposed sanctions on Russian energy companies.

Tyler Pager contributed reporting.

In September 2019, Bill Gates presented Prime Minister Narendra Modi of India with an award on behalf of his philanthropic organization, the Gates Foundation, for the Indian leader’s work on improving sanitation.

An uproar followed.

Three Nobel Peace Prize laureates wrote to Mr. Gates, arguing that Mr. Modi, who was given the award on the sidelines of the United Nations General Assembly in New York, did not deserve the recognition because democratic and human rights had eroded under his rule. “This is particularly troubling to us, as the stated mission of your foundation is to preserve life and fight inequity,” the laureates wrote.

The outrage did little to deter Mr. Gates and Mr. Modi, who have developed an unusually warm and high-profile relationship in the past decade.

They have met several times, and Mr. Gates has been nothing but complimentary of Mr. Modi. Last year, just before a national election, Mr. Gates sat down with the prime minister for an extended televised exchange that Mr. Modi used to burnish his image as a tech-savvy leader.

The relationship between Mr. Gates and Mr. Modi, according to observers, former foundation employees and critics, yields benefits for both men. Mr. Gates is set to visit India in the coming week, his third visit in three years, and will meet with government leaders and others to discuss India’s innovations and progress.

“This trip will give me a chance to see what’s working, what’s changing and what’s next — for India and the foundation,” Mr. Gates wrote on GatesNotes, his personal blog.

India is central to Mr. Gates’s philanthropic work, which makes it essential for the Gates Foundation to stay on the good side of a government that has cracked down on organizations backed by foreign donors. With the vast number of Indians in dire poverty, global development goals cannot be met without progress in India.

The Gates Foundation’s continued access to India has become all the more important as President Trump has withdrawn the United States from the World Health Organization and gutted the U.S. Agency for International Development. The W.H.O., which supports a range of public health programs in India, is facing budget cuts after the United States’ exit. The Gates Foundation, a behemoth in global public health and development, is among the top donors to the W.H.O.

For Mr. Modi, an endorsement from Mr. Gates — the very face of the computer age to many Indians — is a way to connect the Gates technological legacy to the digital economy championed by the Modi government, a pillar of its “Developed India” policy.

Mr. Modi’s desire to harness technology for growth personally resonated with Mr. Gates, given his deep belief in the power of innovation for progress, according to posts he has written on GatesNotes and two former employees with direct insight into the foundation’s activities in India. They spoke on the condition of anonymity to avoid jeopardizing professional relationships.

Representatives of the Gates Foundation and Gates Ventures, the philanthropist’s private office, did not respond to requests for comment. A spokesman for India’s Ministry of External Affairs had no immediate comment.

Mr. Gates has ample company in embracing Mr. Modi, with political and business leaders across the West courting India as a rising geopolitical and economic power. In doing so, many have turned a blind eye to the Modi government’s assault on the country’s secular foundations, its demonization of India’s Muslim minority and its silencing of civil society.

Globally, the recognition from Mr. Gates brings attention to Mr. Modi for his development work rather than his Hindu nationalist politics. Domestically, the relationship has potential political benefits for Mr. Modi.

“The tech-driven sections of the Indian middle class, they grew up with Gates as this iconic figure,” said P. Sainath, an activist who is the founder and editor of the People’s Archive of Rural India, an independent digital media outlet. “Being in good with Bill Gates doesn’t hurt your image with those classes.”

Each Other’s Cheerleader

India’s ties with Mr. Gates and with Microsoft, the company he co-founded, run deep. Satya Nadella, the chief executive of Microsoft, is from India. In January, Mr. Nadella announced plans to invest $3 billion in India, including in artificial intelligence, to help further Mr. Modi’s vision. Mr. Gates has visited India more than a dozen times over the decades, including as Microsoft’s chief executive.

The Seattle-based Gates Foundation, which was started in 2000, opened its India office in 2003 and has invested more in the country than anywhere besides the United States. This year, the foundation’s board of trustees will meet in India as it celebrates its 25th anniversary.

The foundation has partnered with successive Indian governments, supporting public health initiatives, such as polio eradication. It also works closely with the governments of Uttar Pradesh and Bihar, two populous and impoverished Indian states. Mr. Gates sat down with previous Indian prime ministers, including Mr. Modi’s predecessor, Manmohan Singh. But the conversations were typically focused narrowly on the foundation’s work in India.

Mr. Gates hit it off with Mr. Modi during their first meeting in 2014, talking for twice as long as scheduled, according to a GatesNotes post. He said he was impressed with Mr. Modi because of their shared focus on public health, in particular sanitation. Toilets were “high on the agenda, along with vaccines, bank accounts and health clinics.”

Open defecation and waste management remain huge challenges in India, a country of 1.4 billion people. Mr. Modi’s government launched the Swachh Bharat Abhiyan (Clean India Mission), and by 2019, it claimed to have built more than 100 million toilets. That was the work for which the foundation gave him the award, drawing a backlash.

When Mr. Gates traveled to India in 2023, he said his sit-down with Mr. Modi was the “highlight” of his visit and commended him on the country’s digital payments system. “The country is showing what’s possible when we invest in innovation,” he wrote on GatesNotes.

Several people with knowledge of the foundation’s affairs said some employees were unnerved by Mr. Gates’s embrace of Mr. Modi, arguing that the foundation could have pursued its goals and aligned with the government’s objectives without Mr. Gates’s becoming a cheerleader for the prime minister.

Mr. Modi has also heaped praise on Mr. Gates, saying that his government valued the foundation’s expertise and its data- and evidence-driven approach. In 2020, when they met virtually during the pandemic, Mr. Modi encouraged the foundation to “take the lead” in analyzing health care and education changes needed in a post-Covid world.

Last March, three weeks before an election in which Mr. Modi was seeking a third term, he invited Mr. Gates to his official residence for a chat about the country’s progress in using technology to improve the lives of Indians.

The government had planned to air the entire meeting on national television, which reaches more than 650 million people. But the Election Commission told the public broadcaster that doing so would give Mr. Modi’s party an unfair advantage, according to a report in The Economic Times, an Indian newspaper. In the end, only parts of Mr. Modi’s chat with Mr. Gates was aired on television, although it was streamed in full on the website of Mr. Modi’s Bharatiya Janata Party.

A spokesman for the Election Commission said he did not have information about the event. Rajiv Kumar, the chief election commissioner at the time, did not respond to requests for comment.

Tight Grip on Foreign Donors

India has long relied on foreign donors to meet its goals. Organizations like Amnesty International, Rotary International, the Red Cross, Oxfam, U.S.A.I.D. and Greenpeace, as well as various United Nations bodies and private groups like the Ford, Rockefeller and Gates Foundations, provided funding to a thriving local community of nongovernmental organizations or worked alongside them.

But as the Modi government grew increasingly intolerant of any criticism or challenge, including from overseas, Indian laws that regulate the flow of foreign donor funds into domestic nonprofits grew more stringent and were applied more frequently.

A year after Mr. Modi became prime minister in 2014, the government launched a crackdown on foreign organizations, starting with Greenpeace. Many began to scale back their activities or take steps to ensure that their agendas were aligned with the government’s goals.

In 2017, the Indian government accused the Public Health Foundation of India, one of the country’s largest nonprofit groups, of misusing funds and revoked a license allowing it to receive foreign contributions. The Gates Foundation was a big donor to the organization. The health nonprofit regained its license in 2021.

The Gates Foundation has made it clear that its role is to help the Indian government meet its objectives by offering expertise in priority areas like ensuring access to financial services for the poor, female-led development, public health and climate change.

The foundation hewed closely to that message after the controversy over the award it presented to Mr. Modi.

At the time, the foundation said its award was narrowly focused on sanitation goals.

Not long after, Mr. Gates met with Mr. Modi in India. According to a government news release at the time, Mr. Gates reinforced his foundation’s commitment to supporting the goals of the Indian government.

It was the site of the worst aviation disaster on South Korean soil. Now the terminal at Muan International Airport serves as a community center for grieving relatives of the 179 people who perished in the crash. Families gather here to talk, eat together — some even stay overnight in tents.

It was in that cavernous building in southwestern South Korea that the families waited anxiously for news after Jeju Air Flight 7C2216 crash-landed on Dec. 29. Then there were tears and outbursts of anger as officials periodically read out the names of the dead, many identified by DNA tests.

“We’re a family now,” said Son Joo-taek, who lost his son in the accident and was among around 20 people who sat around a row of folding tables that held water and snacks on a recent Saturday. “The people here understand what others just can’t.”

Lately, the talk among some of the grieving families has turned toward action: They want to find out what caused the crash. The jet — carrying mostly vacationers home from a year-end trip to Thailand — belly-flopped onto the runway and sped along until it hit a concrete berm and exploded into flames, leaving just two survivors.

Relatives of those killed say they are unhappy with the trickle of information from officials, and the refusal to release records, including transcripts from the control tower. They want to know more about the reports of a bird strike a few minutes before the landing, how the jet came down without its landing gear, and why the berm it hit was not designed to give way.

In desperation, some have turned to books and videos to learn about aviation safety, including how flight recorders, air traffic controllers, localizers and jet engines work. They are also looking into airport design.

“The families’ first priority is to get the truth,” Son Ha-yang, the daughter of Mr. Son, said at the airport where her brother and his girlfriend were killed. “Otherwise, we’re only relying on the investigators, who often use jargon.”

Ms. Son, who has taken about three months’ leave from her job in Seoul, said she felt the need to read Boeing manuals and aviation regulations, and has been studying terms that had previously meant nothing to her: C.V.R., F.D.R., I.C.A.O. She has been in touch with other relatives who also said they wanted to learn more about what could have gone wrong.

South Korean authorities have said it could take more than a year to complete the investigation, which has faced hurdles that have frustrated the families. Among them: The jet’s flight recorders stopped recording for the final four minutes of the flight.

“The families want to know why their loved ones died,” said Park Cheol, a lawyer for the families. “They also feel that, by studying, they are making an effort for those who died.”

Some relatives have challenged officials at meetings over the crash. They say they are concerned there are not enough people investigating the cause, compared with instances in the United States. Nor have the authorities acceded to their request to release communications from the control tower around the time of the crash.

South Korea’s transport ministry said in a statement that the investigative body was in talks with authorities to increase the number of investigators. The ministry was also considering providing a transcript of the air traffic control communications, though they were not typically released to the public, it said.

Kim Yu-jin has been watching YouTube videos and reading books about past aviation disasters since her parents and her brother died in the crash. She has been looking at the safety features planes have when making emergency landings.

At Ms. Kim’s cafe, in the southern county of Jangheung, her mother, Jung Sun-suk, was the barista and helped package deliveries. Her father, Kim Deok-won, helped transport strawberries and milk, and had planned expanding their 350-square-foot shop.

She said her parents also helped raise her four children. After the crash, she temporarily closed the cafe to focus on her children and deal with the grief.

“Everything has my parents’ touch,” she said. “There are traces of them everywhere.”

After losing his son and daughter-in-law, Lee Jung-keun has focused his personal research on one specific factor: the concrete berm. Most airports worldwide do not have similar structures so close to runways, and when they do, they are made of more fragile materials meant to break apart upon impact, experts have said.

Mr. Lee scoured the internet for information about the berm and became convinced that it was the biggest factor in the high death toll.

“If it weren’t for the berm, almost everyone would have survived,” he said during a visit to the airport with his wife, Lee Mi-jung.

His son, Jae-hyeok, and the younger man’s wife, Tae Ari, shared a love of fishing and married in 2020. They had been planning to start a family, and Ms. Tae’s private math academy in the southwestern county of Haenam was doing well, Ms. Lee said.

The couple hadn’t originally planned to visit Thailand. But a last-minute offer from a travel agency coincided with their wedding anniversary, Mr. Lee said.

Coming to the airport is a way for some families to find a sense of community when their homes are now defined by absence. Others stay away from the airport, fearing the memories will be too painful, or constrained by work.

The crash left Lee Bong-kyung with a struggling shipyard in the southwestern city of Mokpo that was founded by his father in 2015. Sales have dipped in recent years and Mr. Lee said it was his father’s work ethic that kept the business alive: “All he knew was work,” he said.

When Mr. Lee began working at the shipyard about six years ago, it gave his father more leisure time. The elder Mr. Lee had traveled to Bangkok with a group of childhood friends. His death has left his son crushed personally and professionally.

“We also have a lot of debt and loans to pay off, so I’ve thought about giving up a few times,” he said.

The experience of many of the bereaved families — isolation from friends and colleagues, solidarity with relatives of other victims and a distrust of the government — echoes the aftermath of other disasters in South Korea, including the 2014 Sewol ferry sinking and a crowd crush in Seoul in 2022.

Lee Jeong-bok and his wife, Jeong Hyeon-kyeong, were mourning another young victim. Their daughter, Min-ju, had died after taking a trip with a high school friend. She was in her second year at her first job out of college.

Since the crash, Ms. Lee’s three other children have been helping out their parents more, such as doing the dishes. “They’ve matured quickly,” she said.

Mr. Lee said he and his wife planned to stay at the airport until the cause of the crash came to light. “The investigation needs to be thorough and objective,” he said. “There will need to be accountability and consequences.”

Once the investigation is complete, the families will consider filing lawsuits to hold those responsible for the crash accountable, said Jung Yu-chan, a spokesman for the families.

At the airport one recent Saturday, Jo Mi-young was mourning an entire family that had perished on the jet. Ms. Jo’s sister Mi-Ja was on board with her daughter, the daughter’s husband and their two children.

Ms. Jo said the children’s father, Na Byung-hwa, had taken his family to Bangkok for a triple celebration: He had recently been promoted at his job at an agricultural cooperative, his wedding anniversary was approaching and his mother-in-law recently had her 60th birthday.

“Who else will remember this family?” Ms. Jo asked.

Her brother, Jo Hyo-seon, said that he and his sister had stayed at the airport almost every day since the crash, finding solace in their shared experience with other families.

“Only here can we cry, only here can we laugh,” he said. “We’re not leaving until the truth is told.”

Serhii Kovalov doesn’t like sushi. Nor does the sushi chef at his restaurant in eastern Ukraine.

But when customers started asking for it, Mr. Kovalov navigated both enemy shelling and ordinary supply-chain issues to get fresh fish for Philadelphia rolls to his frontline town, Sloviansk.

Now, as Russian forces have drawn closer and life gets more bleak, many Sloviansk residents are weighing whether to flee. Not Mr. Kovalov. He’s determined to keep serving sushi to soldiers and civilians who are seeking comfort, sustenance or a taste of something special after more than three years of war.

“I know I’m needed here,” the 30-year-old Mr. Kovalov said, gesturing at the restaurant and the town outside that has long been in Russia’s cross hairs. “So I stay.”

Sushi has long been wildly popular in Ukraine, and for people in Sloviansk, this treat provides a sense of much-needed normalcy.

When Sloviansk came under attack in February 2022 when Russia’s full-scale invasion began, sushi wasn’t even on the menu at Mr. Kovalov’s restaurant, Slavnyi Horod, or “Glorious City.”

His was the only restaurant in town that stayed open in the early days of the war, and suppliers would not deliver.

“So we began building entirely new logistics routes,” Mr. Kovalov said. Colleagues relocated to central and western Ukraine, setting up new vendor relationships. To get goods back across the active front line to Sloviansk, Mr. Kovalov sometimes drove round-trip himself.

As people fled, the restaurant’s staff dwindled from 35 to seven and became a “family,” Mr. Kovalov said.

With no water or electricity, meals were cooked outside on a fire. Eventually, the restaurant purchased a generator and drilled a well, with Mr. Kovalov intent on keeping its doors open.

Even after a missile destroyed his apartment, Mr. Kovalov headed to the restaurant — with a concussion.

“That was probably the toughest day, having to pull myself together while walking to work. I had to quickly decide: either leave, or stay and lead the team through this,” he said. “I walked in with a smile and said, ‘It’s fine. We got lucky this time — second birthday. Let’s keep working.’”

Amid all that hardship, why would he introduce sushi — which requires special storage and refrigeration — to the menu?

“It started with demand,” he said simply, betraying his business school degree. “There were no sushi restaurants in the city, and guests began asking.”

“Whether I enjoy it or not doesn’t matter,” he insisted.

Today, he has partners in Kyiv who inspect and select “very fresh” raw fish, which is then shock-frozen and packed into cooled containers for the eight-hour overland journey to Sloviansk.

The road weaves through Kharkiv, then Izium, cities whose smashed buildings tell the tale of Russian bombardment, occupation and bitter fights for liberation. It passes a snow-covered forest once filled with mass graves of the invasion’s victims, and it runs close enough to occupied territory to pick up Russian stations on the radio.

From Izium, it’s about 40 minutes down the highway and into Donetsk, the region that is home to Sloviansk. Russian forces have captured a large part of Donetsk and aim to seize all of it.

The fish trucks enter Sloviansk on the north edge of town, where a salt lake in better times drew tourists seeking spa treatments. Many of the spa buildings have been reduced to rubble, and soldiers mill around in the ruins.

Anti-tank barriers line the road into the city center as one-story brick houses give way to apartment blocks, some disfigured from attacks.

Despite the scars, Sloviansk is bustling. Cars honk, soldiers shop for groceries and children wave at ducks in the park.

But pressure is mounting from heavy fighting nearby. Russian forces are pushing to capture Chasiv Yar, a city 30 miles away. Doing so could help clear the way to take Kramatorsk — putting neighboring Sloviansk next in line, residents fear.

Zoya Trubytsyna, 68, said her suitcase was already packed.

“The front line is coming closer,” she said while walking to work. “If something happens in Kramatorsk, we will all leave.”

Life is already getting more difficult, she said, with power cuts and near-nightly explosions.

But Mr. Kovalov still manages to keep his restaurant open for breakfast, lunch and dinner.

As he stirred a coffee and chatted with servers, a morning crowd filled the seats. No one stopped eating when an air-raid warning wailed.

Blue takeout bags decorated with handwritten hearts were lined up behind the cashier for when the lunch rush started about an hour later.

A long deli counter featured hot food, salads and sweets. The sushi station sat at the end, with photos of maki and tempura hanging above.

A soldier added a Philadelphia roll to his loaded tray of sauerkraut, blood sausage and lasagna.

“Honestly, the sushi here isn’t that tasty,” the 33-year-old soldier, who goes by the call sign “Siesta,” said after polishing off his plates. But “it’s a way to feel something familiar, like being at home.”

As a civilian, Siesta said, he would go for sushi with friends in Kyiv. But with his mechanized battalion defending the nearby city of Lyman, the food options are basic. Coming to Sloviansk for “that little bit of soy sauce,” he said, was a rare treat.

Slavnyi Horod is no longer the only sushi spot in town; there are several. Three blocks away is “Big Roll,” which was closed for months after the full-scale invasion. Since reopening, business has been unsteady, said its owner, Nataliia Gordienko, who now keeps only a short-term supply of fish.

“We don’t know what will happen next,” she said while boxing salmon rolls. “What’s the point of stockpiling if power gets cut off?”

People are also scared of Russian strikes, she added, ordering “quickly, quickly” when they come in for takeout.

Of 21 rolls on offer at Mr. Kovalov’s restaurant, the Philadelphia roll — with salmon and cream cheese — is the most popular, according to the sushi master, Dmytro. He seems baffled by its popularity — “it doesn’t really exist in nature” — but has never been a sushi fan himself.

“Raw fish always raises suspicion,” he said, smirking.

Still, Dmytro, who asked that only his first name be used for security reasons, finds the work gratifying, and he watches YouTube videos to learn new techniques. But he is not sure he will stick with sushi forever.

“At this point, I don’t feel like planning anything,” he said as a waitress whispered that an order was waiting. “There’s a war in our country, and it’s hard to know what tomorrow or the day after will bring.”

His boss, Mr. Kovalov, is not immune to the uncertainty. He’s aware the front line in Donetsk is under pressure, saying, “We are afraid every day.”

For now though, he said, leaving is not an option.

“Elsewhere just doesn’t make sense,” he said. “I’ve already found my purpose right here.”

Oleksandr Chubko contributed reporting.

As families of victims mourned the loss of loved ones and kept an anxious vigil in hospitals on Monday, the authorities in North Macedonia said they were investigating possible official misconduct in the case of a deadly inferno that killed at least 59 people.

Officials said that Club Pulse, the nightclub where the fire broke out early Sunday, was operating with an illegally issued license document, and that it lacked proper escape routes. The building’s roof was set ablaze by fireworks used during a concert, officials have said. At least 155 people were injured in the inferno that swept through the venue.

“I will have no mercy,” Prime Minister Hristijan Mickoski said on Sunday, adding, “There is no person in Macedonia who is not broken and with a destroyed spirit after this.”

Mr. Mickoski, who took power in June, said the club, which was in Kocani, about 50 miles east of the capital, Skopje, had a license document that had been issued “for a bribe.” He said the document bore the seal of the economic ministry and the signatures of former officials there, and that it was “issued illegally.”

“This is the culmination of a bad, neglected system,” Mr. Mickoski said, describing North Macedonia’s effort to root out corruption, which the European Commission described in a 2024 report as a “serious concern” in the country.

The building that housed Club Pulse was registered as an industrial facility — not a hospitality venue — but had still received a hospitality permit from the economy ministry, the public prosecutor, Ljupco Kocevski, said on Sunday.

Prosecutors are seeking to arrest a former economy minister, Kreshnik Bekteshi, according to MRT, a state-run news agency. Mr. Bekteshi did not respond to a request for comment. Officers detained another former official from the ministry, as well as other officials in other government agencies.

Ljupco Papazov, the Kocani mayor, resigned on Monday. “The shock and brokenness I feel will last my entire life,” he said on Facebook.

Some parents who had lost children in the inferno had expressed fury with Mr. Papazov for maintaining a low profile the previous day. “Why is the mayor not here?” shouted Dragi Stojanov, whose only child died in the fire, in a video from The Associated Press.

In an online direct message, Mr. Papazov said he had been busy coordinating aid after the tragedy, and that he had resigned for unspecified “moral reasons.”

Mr. Stojanov said he had no reason to live after his 21-year-old son was killed. “I lost everything,” he said.

Mr. Stojanov’s son was one of many young people who had come to Club Pulse to see DNK, a popular North Macedonian group.

As the band performed, sparklers were set off around them, video shows. Those sparklers, officials said, were used illegally and appear to have started the fire. “The pyrotechnic devices used in the nightclub were brought by the band,” the country’s interior minister, Panche Toshkovski, said.

“Unfortunately,” he said, “the person who was responsible for handling them has passed away.”

One member of DNK died, as did other artists performing that night, Biljana Arsovska, a spokeswoman for the public prosecutor, wrote in an email. She said officials had not finished identifying victims.

“I feel as if someone hit me with an aluminum baseball bat,” Tijana Dapcevic, a Macedonian singer who knew some of the victims, said in an interview.

She said a friend of hers, Sara Projkovska, had died in the fire. Ms. Projkovska was a professor at Cyril and Methodius University in Skopje, which announced her death in a Facebook post with her picture, smiling under a mane of hot pink hair.

On Monday afternoon, thousands of people gathered in Skopje at the university, in honor of the fire’s victims, news footage showed. Many also gathered to protest in Kocani, news footage shows.

Pictures of the victims had already begun to appear on Macedonian social media, like a yearbook of people whose lives were cut short amid flames and smoke.

One was Petar Ivanovski, a young man with thick eyebrows and a smile, whose university confirmed his death in a Facebook post.

Another, Andrej Lazarov, 25, was a professional soccer player. He was remembered by his team, F.C. Shkupi, in a Facebook photo that showed him playing.

“A lot of children have suffered,” Simeon Sokolov, whose daughter was on a respirator after inhaling smoke, told the Serbian television channel N1 on Sunday night.

“The doctors are doing all they can,” Mr. Sokolov added, “but there are too many injured.”

Many, furious and grieving, pointed to what they saw as gross negligence at the club.

There were no side doors for evacuation, said Mr. Kocevski, the public prosecutor: “Instead, there was only one improvised metal door at the back, which was blocked from the inside.”

The nightclub did not have a functioning hydrant, he added. There were only two fire extinguishers, which he said was not enough for the size of the space.

Jon Hazell contributed reporting.

Rwanda severed diplomatic ties on Monday with its former colonial ruler, Belgium, which has been pushing to penalize Rwanda over its invasion of the neighboring Democratic Republic of Congo.

Rwanda’s Foreign Ministry gave Belgian diplomats 48 hours to leave the country.

The diplomatic escalation came as the European Union, at the urging of Belgium, on Monday imposed sanctions against Rwandan military and government officials for their involvement in the conflict in Congo.

“Belgium has clearly taken sides in a regional conflict and continues to systematically mobilize against Rwanda in different forums,” Rwanda’s Foreign Ministry said in a statement.

The European Union accused Rwandan officials of fueling the conflict through the presence of Rwandan troops in eastern Congo and the plundering of Congo’s mineral resources. The sanctions were Europe’s first steps toward increasing pressure on Rwanda, though so far it has maintained close cooperation on security and strategic minerals.

“Belgium has been taking the lead in Europe in advocating for sanctions against Rwanda,” said Kristof Titeca, a professor of international development at the University of Antwerp. At the same time, he added, “the European Union did the minimum with these sanctions on individuals — it still remain pretty harmless.”

The Belgian foreign minister, Maxime Prévot, said in a statement that Rwanda’s response “is disproportionate and shows that when we disagree with Rwanda, they prefer not to engage in dialogue.” He said Belgium would respond in kind to the expulsion of its diplomats.

The United States, the European Union and the United Nations say Rwanda has been funding, supporting and commanding an armed rebel group, M23, that has fought government forces in eastern Congo for more than a decade and launched a new offensive there in January.

M23 now controls the region’s two largest cities, border crossings with Rwanda and access to key natural resources, including one of the world’s largest coltan mines. Coltan is a mineral that is vital to making smartphones and other electronic devices. M23 is in charge of an area in eastern Congo that is the size of Greece or Louisiana.

After the E.U. imposed sanctions, M23 said in a statement on Monday that it would not participate in peace talks with Congolese government officials that had been scheduled for Tuesday — what would have been the first official meeting between the two warring parties in years.

The latest wave of violence has killed thousands and displaced more than 500,000 people since the beginning of the year, according to the U.N.’s refugee agency.

Despite widespread evidence shared by U.N. experts and independent researchers that thousands of Rwandan troops are deployed in Congo and that Rwanda supplies weapons to M23, Rwanda has denied backing M23.

Rwanda, a country of 14 million whose economic growth is often viewed as a success story in Africa, remains heavily dependent on external assistance. More than a quarter of its national budget of $4 billion comes from foreign aid, according to the World Bank — about $1.25 billion on average over the past several years.

Britain and Germany have withheld aid to Rwanda, and Canada has suspended some export activities.

On Monday, the European Union imposed sanctions on a Rwandan gold refinery and five Rwandans, including Francis Kamanzi, the chief executive officer of the Rwanda Mines, Petroleum and Gas Board. The bloc has accused Rwanda of mixing minerals plundered from Congo with its own production.

Also sanctioned were Ruki Karusisi, the commander of Rwanda’s special forces, which U.N. experts say oversee M23 units on the ground; and two high-ranking military officials, Désiré Rukomera and Eugene Nkubito.

Yet, Rwanda’s government has mostly remained defiant, and on Monday it accused Belgium of “neocolonial delusions.” Over the past decade, the East African country has cultivated economic and military relationships with a wide range of countries — including Singapore, Turkey and Qatar — beyond its traditional Western partners.

It has portrayed itself as a safe and stable haven in a volatile region, attracting tourism and investment. Last month, finance executives from across Africa met in Rwanda’s capital, Kigali, for a financial technology conference, and cyclists from across the world raced through the country’s lush hills as part of the Tour of Rwanda.

“Rwanda has flexed its muscles at any criticism and signaled, ‘We’re not afraid by sanctions; they’re not having any effect,’” said Mr. Titeca, the professor at the University of Antwerp. “But that strong reaction actually shows that it might have some effect.”