In a remote corner of northeast Colombia, where dirt roads lead to lush hills lined with banana trees, farmers and their families have become the victims of a spate of violence unlike anything the country has seen in a generation.

As two rebel groups battle for territory, more than 54,000 people have fled their homes, and an estimated 80 people died in a matter of days, with the death toll expected to climb.

At the root of this conflict are decades-old battles over land and drug money, and the failure of past deals to lead to lasting peace. But analysts, diplomats and even Colombia’s president, Gustavo Petro, point to another, newer factor helping foment the chaos in Colombia: neighboring Venezuela.

Over the past decade, as Venezuela has descended into autocracy, its government has also drawn closer to the principal aggressor in the current conflict next door, a longstanding rebel group called the National Liberation Army, or ELN.

Born as a Marxist group in Santander, Colombia, in the 1960s, the ELN has increasingly used Venezuela as a place of refuge, moving deeper into the country, enriching itself through drug trafficking and other illicit activities, tripling in size to roughly 6,000 fighters and strengthening relationships with Venezuelan officials.

In return, the Colombian authorities say, the country’s autocratic president, Nicolás Maduro, who has become more isolated on the global stage, has benefited from having a powerful armed group as a buffer against domestic and foreign threats, including the possibility of a coup.

For years, the disintegration of Venezuela’s democracy has put a strain on neighboring Colombia, sending some three million refugees fleeing into the nation of just 50 million.

Now, some say, Mr. Maduro’s Venezuela is being used as a base to unleash something far more destabilizing: a new wave of destruction in Colombia.

Mr. Petro went as far as accusing the ELN of becoming a “foreign force,” that had invaded Colombia. “This is a problem of national sovereignty,” he said, “not just an internal conflict, which we’ve had since long ago.”

Venezuela’s defense minister, Vladimir Padrino López, in a statement in late January, said it was “essential to state with crystal clarity that Venezuela does not serve, nor will it ever serve, as a platform for armed groups outside the law, whatever their nature, ideology or nationality.”

Why the ELN decided to attack now is unclear, but the relationship between Mr. Petro and Mr. Maduro, once friendly, has soured significantly over the last few months.

Mr. Petro is Colombia’s first leftist president, a former guerrilla himself and seemingly a natural ally of Mr. Maduro, who calls himself a socialist. Two years ago, they held a high-profile meeting in Caracas, where the two promised to work together on issues of mutual interest.

That included the security of their 1,300-mile shared border.

Then in July, Mr. Maduro declared himself the winner of a tainted presidential election, refusing to produce tallies to back up this claim and imprisoning roughly 2,000 people amid a wave of protest.

The United Nations and other independent monitors questioned the result. The United States recognized the opposition candidate as the winner.

Soon, Mr. Petro, one of few leaders to still be somewhat amicable with Mr. Maduro, took a more critical tone, publicly urging him to publish election results and release political prisoners. Mr. Maduro responded by ordering a “punch in the face” to anyone who meddled in Venezuela’s affairs.

When Mr. Maduro was sworn in for a third term on Jan. 10, Mr. Petro refused to attend the ceremony or to recognize the Venezuelan as president.

Five days later, the ELN sent fighters from a more southern point in Colombia into northern Colombia, to a strategically important region called Catatumbo, saying on X that it sought to oust a rival armed group called the 33rd Front.

The two groups had long divided control of the region, home to vast fields of coca, the base product in cocaine. Now, a fragile power-sharing accord had broken.

The violence has crushed Mr. Petro’s chances at accomplishing one of his most important policy goals: a peace deal with the ELN, a key part of an ambitious campaign promise — “total peace,” he called it — that he made to end all conflict in Colombia.

The country has suffered decades of internal violence that has claimed hundreds of thousands of lives.

“‘Total peace’ was already in a bad spot,” said Kyle Johnson, co-founder of Foundation Conflict Responses, a nonprofit research group in Bogotá. “With this outbreak of violence it feels politically like the final nail in the coffin.”

Today, tens of thousands of civilians are trapped in the middle of the violence. Some families in Catatumbo have sought refuge in the forest, surviving on whatever they managed to carry with them.

Others have streamed into Tibú, a small Colombian town on the Venezuelan border, sleeping in a school that has become a shelter. Still others have crowded into a coliseum in Cúcuta, the region’s main city, lining up each morning for food and assistance.

On a recent day at the school in Tibú, classrooms had become bedrooms, and children played while a young woman, overcome with emotion, cried and wheezed until she fainted on a patio floor.

“Sow what you dream,” read a mural on one wall. Military helicopters buzzed overhead.

Venezuela’s powerful interior minister, Diosdado Cabello, had just paid a visit to the border, while a new wave of Colombian troops were moving in to fight the ELN.

As the sun set, Luz, 45, and her husband Francisco, 40, sat in the doorway of one of the classrooms, describing the home they had abandoned: dirt floor, wood construction, a small patio, a barrel for collecting rainwater.

Just days before, as armed men had stormed the region, a man had arrived at the school where Francisco worked and told him that he had five minutes to leave.

The couple and their two sons ran.

The Times is publishing only their first names, out of concern for their safety.

That night in Tibú, Luz was struggling to understand how they had gotten there.

“All of us civilians are saying: What are they fighting for?” she said. “What are they looking for? What is the reason for this?”

At his office in Cúcuta, Gen. Mario Contreras, the regional commander for the Colombian Army, said the violence had begun with the killing of a single family, which angered the ELN. The following day, he said, the ELN entered town centers — “because they know people are defenseless there” — armed with pistols and dressed as civilians, looking for suspected collaborators of the 33rd Front.

A generation ago, the ELN was so weak it was near extinction, battered by the Colombian state and paramilitaries. In a recent academic paper, two researchers, Jorge Mantilla and Andreas Feldmann, argued that “the support of neighboring Venezuela” has been the most important factor in the rebels’ “improbable resurgence.”

Bram Ebus, a consultant for the International Crisis Group, said that the Venezuelan government had in recent years even used the ELN as “an extension” of its security forces. “We know that there is a tacit alliance on the federal level in Venezuela,” he said.

The Colombian military says ELN fighters passed through Venezuela to get to the scene of their first attacks. In a message on X, signed by the Central Command of the ELN, the group called this “fake news” invented by the Colombian government to justify a possible invasion of Venezuela.

The group has focused its anger on the Colombian government, which it accused of uniting with the 33rd Front to “annihilate” the ELN.

The 33rd Front is a faction of the Revolutionary Armed Forces of Colombia, or FARC, who remain in arms despite a 2016 peace deal signed by the FARC and the Colombian government.

In late January, Colombia’s defense minister traveled to Venezuela to meet with his Venezuelan counterpart and said afterward that the two had discussed “cooperation” in capturing ELN leaders and containing the group.

As the violence unfolded in recent days, something remarkable started happening at the River Tarra, a muddy strip dividing Colombia and Venezuela. For years, Venezuelans had poured across it, seeking sanctuary in Colombia. Now, the flow was going in reverse.

At one crossing, a makeshift ferry carrying roughly nearly 3,000 people into Venezuela in the first three days of the fighting.

Jackline, 42, was one of them. Wearing a red skirt adorned with buttons and a blue blouse — more suitable for church than an escape — she was with her son, 7, and daughter, 17.

Jackline had been displaced once before by violence, she said. And though she is Colombian, she was now considering staying in Venezuela for good.

“It’s really nice there,” she said. “There is no war.”

Genevieve Glatsky contributed reporting from Bogotá.

The first senior Trump administration official was expected to visit Ukraine, a day after Russia released an American prisoner in a development that President Trump called a positive signal for cease-fire talks.

Treasury Secretary Scott Bessent’s trip comes amid anxiety in Kyiv and among American allies about whether U.S. support for the Ukrainian war effort will be maintained now that Mr. Trump has returned to the White House.

The Trump administration has already sought an arrangement for the United States to secure rights to Ukrainian natural resources, including rare earth minerals, as a guarantee for further U.S. assistance.

Mr. Trump said in a post on Truth Social on Tuesday that he was sending Mr. Bessent to Ukraine because “this war must and will end soon — too much death and destruction.”

Mr. Trump, who has made American spending in a variety of areas a focus of the early days of his new administration, also wrote that the visit would touch on American assistance to Ukraine. The United States, he wrote, had spent billions of dollars “with too little to show” for it.

President Volodymyr Zelensky of Ukraine said he welcomed the visit by Mr. Bessent. “We are already prepared for meetings with representatives of the United States — negotiations will begin soon,” Mr. Zelensky in his evening address to Ukrainians on Tuesday.

Mr. Trump’s focus on securing the mining rights was reflected in the choice of Mr. Bessent to make the first high-level visit, rather than a senior security or military official to discuss the war.

Hours after Mr. Trump announced the visit, Russia launched a missile attack on Ukraine that included a volley of ballistic missiles fired at Kyiv, the capital.

The missile strike, which took place shortly before 5 a.m., killed one person and wounded four others, including a 9-year-old girl, according to the Kyiv city administration. It was unclear if Mr. Bessent was in Kyiv at the time.

Falling debris from interceptions by air defense missiles over Kyiv scattered debris that caused fires in buildings in four districts, and explosions echoed through the capital for several minutes.

The missile volley in Ukraine came also hours after Russia released an American prisoner, Marc Fogel, in what Mr. Trump said he hoped would be an initial step toward negotiating an end the war in Ukraine.

Mr. Zelensky, in a post on X, also voiced support for ending the war. “This Russian terror against Ukraine will not stop on its own,” he wrote. “Right now, we need the unity and support of all our partners in the fight for a just end to this war.”

Overall, Russia fired six ballistic missiles and 123 exploding drones at Ukraine overnight, after a period of nearly a month in which Russia has largely refrained from using ballistic missiles. Fighting also continued along the front line in eastern Ukraine, where Russian forces continued assaults.

The Ukrainian military reported that 149 aerial bombs were dropped from airplanes and more than 2,000 short-range drone strikes were fired at frontline positions.

In another missile attack on Ukraine, on Tuesday, Russia struck the country’s main natural gas producing region, Poltava, continuing attacks on the country’s energy infrastructure.

Beyond Ukraine, the Polish military reported on Tuesday that a Russian military plane briefly entered its airspace, although the military said that it was in contact with its Russian counterparts. The error was attributed to a problem with the plane’s navigation system.

A Russian special forces commander served on four battlefronts across eastern Ukraine after joining Russia’s invasion nearly three years ago. He said the most ferocious fighting he has seen is now unfolding back home, as the Russian Army he serves struggles to liberate a sliver of national territory from Ukrainian forces.

The protracted battle for the occupied Russian town of Sudzha and the surrounding countryside has unexpectedly emerged as one of the focal points of a war fought over the fate of the Ukrainian state. Both sides have committed a significant share of their limited reserves to control Sudzha, a once sleepy county seat in the Kursk region, near the two countries’ border.

“These are the most brutal battles — I haven’t seen anything like this during the entire special military operation,” the commander, who leads about 200 men fighting in Kursk, said in an interview near the front line late last year, using the Kremlin’s euphemism for the war. He requested that he be identified only by his call sign,Hades, according to military protocol.

Both sides see Kursk as must-have territory, an important element in the expected peace talks promised by President Trump. Military analysts say the Ukrainian forces have since poured some of their best reserves into Kursk, hoping to use its conquest as a bargaining chip in negotiations.

For President Vladimir V. Putin of Russia, the Ukrainian incursion — the first invasion of Russian territory since World War II — has been an ongoing embarrassment. He is determined to push Ukraine out so he does not have to make any concession to get the territory back, and Moscow has deployed tens of thousands of soldiers, including conscripts and North Korean allies, to repel the invaders, according to U.S. officials.

Ukrainians “wanted to conduct the talks from a position of strength,” Lt. Gen. Apti Alaudinov, the commander of the Akhmat special forces unit from Russia’s Chechnya region, said in an interview in the Kursk region in December. “When the time comes for the talks, it is not clear if they can still say that they are here.”

With the stakes so high, Russian soldiers fighting in Kursk believe the fighting is about to become even bloodier.

“We are expecting Bakhmut 2.0,” said Hades, the Russian commander serving in Akhmat, which is made up in large part from the remnants of Wagner paramilitaries.

Bakhmut is a Ukrainian town whose ruins Wagner captured in 2023 after a nine-month assault at the cost of tens of thousands of casualties. The standoff was emblematic of Ukraine’s stand-and-fight strategy even in the face of Russia’s superior manpower and firepower.

Another Russian commander, who insisted on anonymity for security reasons, said the cost of a showdown would be staggering. The bloodshed, the casualties, it’s “unimaginable,” he said.

A photographer working for The New York Times was given access to Kursk late last year and was allowed to interview and photograph Russian soldiers at a hospital and near the front line, as well as civilians, some who had fled their villages and others who stayed behind.

Some of the interviewed soldiers were Wagner veterans who joined Akhmat after the failed mutiny of the mercenaries’ leader, Yevgeny V. Prigozhin. They said the Chechnya-based special forces unit most closely resembled the loose structure of their former paramilitary force.

Other interviewed soldiers were recent volunteers who joined to take advantage of rising sign-up bonuses. They said an opportunity to fight inside their own country provided an additional incentive to join a war whose broader goals or causes they struggled to articulate.

“This is our land, these are our people and our values,” Aleksandr, a Russian contract soldier who was injured by a mortar fighting in Kursk, said in an interview at a medical center. “We must fight for them.”

Since the Ukrainian invasion began six months ago, both sides have taken heavy losses in Kursk’s exposed, flat terrain punctuated by small villages, although the armies closely guard their casualty rates. Russia, in glacial advances, has been able to recover about 60 percent of about 500 square miles initially captured by Ukraine.

Between the two armies are an estimated 2,000 to 3,000 Russian civilians, who were trapped by the speed of the initial Ukrainian advance and the Russian government’s failure to mount an evacuation.

The two sides have blamed each other for failing to provide conditions for the remaining residents to leave, forcing those civilians to endure the Russian winter with dwindling food supplies and without running water, heating or electricity. As the Russian forces close in, they are being subjected to escalating bombardment.

The analysts and relatives of Sudzha residents fear that the Russian military’s reliance on heavy bombing and Ukraine’s determination to defend the town threaten a humanitarian catastrophe at a level not seen in Russia since the civil war in Chechnya in the 1990s. By late January, Russian forces stood just a few miles from the town center.

In Ukraine, the Russian invasion has caused civilian suffering on a much larger scale, with strikes on residential buildings, hospitals, churches and an array of energy facilities.

Pasi Paroinen, a military analyst at Finland-based research company Black Bird Group, said the Russian assault on Sudzha would be costly for both soldiers and civilians, because Ukraine had deployed in Kursk its strongest force.

Lyubov, a mother of four, is part of a group of Kursk residents who for months have been publicly calling for a humanitarian corridor to evacuate relatives trapped in Sudzha. She said she feared that the impeding assault on the town would leave her parents and others there with little chance of survival.

“By the time Russian troops enter the settlements, only ruins and ashes remain of the houses,” she said in an interview, adding: “This is an awful rescue system.”

The apocalyptic scenes described by civilians who have escaped Sudzha’s surrounding villages foreshadow the intensity of the impending battle for the town.

In interviews, these civilians provided mixed accounts of Ukrainian occupation.

Zoya, 64, described the initial friendliness of Ukrainian soldiers who occupied her village, Pogrebki, on Aug. 12. She said the first soldiers who came to her house gave her husband a pack of cigarettes and offered their help.

“They were really nice lads,” she said.

(Zola and other civilians who were interviewed are being identified by their first names only to protect them against Russian censorship laws).

That camaraderie waned as the fighting intensified, according to those who fled. The Ukrainian soldiers began to see Russian civilians as a hindrance — or worse, as potential informers who could give away their positions.

Zoya and her husband ran out of food and subsisted on occasional frozen potatoes that they dug out from their garden. During one of those sorties, a drone exploded near her husband. He died in her arms minutes later, she said.

Zoya spent most of her time sheltering from constant bombing in her basement, a stretch of darkness that made her hallucinate and temporarily lose her sense of sight and time. Hunger eventually drove her to attempt an escape.

“There was nowhere left to live — it was so scary there, everything was destroyed,” she said in an interview.

She said she walked five miles through fields littered with destroyed Russian tanks and dead soldiers before reaching the Russian positions in November.

Another woman named Natalia, 69, who uses a wheelchair, recounted a similar experience.

She said Ukrainian soldiers initially brought her bread, water and insulin for her diabetes after occupying her village of Novoivanovka. The soldiers stopped occasionally to chat over a cup of tea.

The treatment worsened as the fighting drew closer.

She said in an interview that her husband had died after being summarily shot by a Ukrainian soldier. Her account could not be independently verified and Ukraine has repeatedly said that it adheres to humanitarian laws in Kursk.

By November, Natalia was sheltering in a basement in no man’s land. One day, she said, a Russian reconnaissance group reached her house and told her that her only chance of survival was escape.

“They said, ‘Please leave, however you can — otherwise you will die,’” said Natalia.

She said other surviving residents helped to carry her to another village, where their group was eventually rescued by Russian troops.

Sudzha residents now fear similar hardships are coming to their trapped relatives.

Earlier in February, a missile hit Sudzha’s boarding school, which sheltered about 100 people displaced from the outlying villages. Both sides have blamed each other for the strike. Ukraine has released evidence that appears to show that Russia was responsible.

The attack killed at least four people; Ukrainian soldiers evacuated survivors to Ukraine.

“We don’t know where the rocket came from,” said Yulia, a Russian woman whose parents survived the strike. She said that Ukrainian soldiers “came and helped dig people from the rubble, and saved our people.”

A Russian man named Sergei said that video messages from family in the town had sometimes reached him following its occupation. Over the months, he said, he watched their hair grow white, their bodies grow thin and the sounds of explosions grow louder.

“I’m sorry that I am crying,” said his sister in a video that was viewed by The Times, congratulating Sergei on his birthday. “I wish I could’ve done it in person, at least by telephone. You have always complained that I call too little.”

“Mother can’t congratulate you, because she struggles to come up the stairs. She is almost always in the basement,” the sister added. “She joins my congratulations.”

Eventually, the videos became too painful to watch, said Sergei, leading him to switch to passing occasional texts.

Constant Méheut and Yurii Shyvala contributed reporting from Kyiv and Milana Mazaeva from Tbilisi, Georgia.

The family of four refugees filled seven suitcases for their new life in America. They packed blankets, tin plates, one blade for clearing the land in their future home and one for chopping meat. They left behind what they were not supposed to bring: slingshots, fish paste, traditional medicines from their native Myanmar.

But the family never made it to Ohio. Last month, their flights were abruptly canceled. Now with President Trump’s order to pause refugee resettlement, even for thousands of those who have gone through the yearslong approval process, they say they have lost hope in ever becoming Americans.

“I don’t have an opinion about American politics,” said Saw Steel Wah Doh, a 35-year-old lab technician, who is now back in a refugee camp in Thailand with his wife and two children. “I want to become American, work hard, love democracy.”

The Trump administration’s refugee suspension and foreign aid freeze are upending efforts to address one of the world’s most dire humanitarian crises. Not too long ago, Myanmar was an icon of democratic reform lauded by the West. Today, four years after the military toppled an elected government, it is an international pariah largely unchecked as it bombs its own civilians.

On Wednesday, nongovernmental organizations that promote democracy and provide lifesaving treatment for refugees and people displaced by conflict in Myanmar said they were told that grants from the National Endowment for Democracy had been suspended, effective immediately.

The N.E.D. was set up by Congress during the Reagan era to strengthen democracy worldwide. Three representatives of Myanmar-related aid groups said they were told that the N.E.D. has not been able to draw funds from the U.S. Treasury to pay for grants that had already been approved.

The N.E.D. stoppage comes two weeks after President Trump’s order to freeze most foreign aid, including funds disbursed by the United States Agency for International Development. Myanmar-related programs received about $150 million in pledges from U.S.A.I.D., according to local monitors. The aid money was to be used for benefits including H.I.V. treatment and support for exiled media reporting on Myanmar’s civil war.

In 2024, Myanmar was the second-most-dangerous and violent place on earth, according to a global conflict monitor. More than 3 million people are now displaced; thousands have been killed.

The United States has long offered a legal path to immigration for refugees fleeing persecution, war or other threats to their lives. Mr. Trump’s directive has shut the door to Afghan translators who risked their lives for American soldiers and to those fleeing religious persecution. It has also dashed the dreams of people from Myanmar, some of whom escaped persecution decades ago.

In Bangladesh, a sprawling tent settlement for Rohingya Muslims expelled from Myanmar constitutes the world’s largest refugee camp. Mohammad Islam was supposed to be resettled in the United States on Feb. 13, along with his family. That dream has withered.

Mr. Islam, 43, has been a refugee since he was 7, but he speaks fluent English and serves as a teacher in the camps.

“I have never been in a classroom, I only studied in tent shelters,” he said. “I want my children to learn in a real school, with walls and desks, in the United States.”

The 2021 coup, which put Myanmar’s generals back in charge, drew bipartisan condemnation in Washington. During Mr. Trump’s first term as president, his administration formally labeled the Myanmar military’s campaign of violence against the Rohingya a genocide. He also honored religious minorities from Myanmar at the White House.

But American support for those fighting Myanmar’s junta has never approached the monetary commitment made to Ukraine, Israel or other top aid recipients. In Myanmar’s jungles, university students, young professionals and even poets who have taken up arms to oust the generals have expressed frustration at how little international attention their plight garners.

In late 2022, President Biden signed into law the BURMA Act, which aims to punish those abusing human rights in the country and to provide assistance to those opposing the junta. (Burma is Myanmar’s former name.).

Last month, Mr. Trump singled out for elimination a $45 million scholarship program that helps Myanmar students fleeing civil war and hoping to study conflict resolution and peace building. Supported by U.S.A.I.D., the educational fund is called the Development and Inclusive Scholarship Program.

“We also blocked $45 million from diversity scholarships in Burma,” Mr. Trump said, adding, “you can imagine where that money went.”

In a post on X, the so-called Department of Government Efficiency labeled the program a “DEI scholarship” and said it had been canceled. Mr. Trump has said federal funds should not be used to support diversity, equity and inclusion.

“It feels like they just shut it down because they could,” said Ko Hlwan Paing Thiha, a scholarship recipient. He has been studying for a master’s in public policy in Thailand.

While opposition militias have pushed the Myanmar military from vast swathes of territory, the junta’s forces have exacted revenge on civilians through a brutal aerial campaign and the scattering of land mines in thousands of villages. The military has enforced conscription and is kidnapping young men from the streets to fill its ranks.

For the hundreds of Myanmar refugees already cleared to go to the United States, the prospect of an indefinite immigration halt is yet another hardship in lives beset by conflict, poverty and insecurity. Saw Htun Htun said his wife and two daughters are already resettled in Vermont. He is supposed to fly to the United States in late February but said he has little hope the trip will go forward.

“My heart is weak, and I am scared that I will never see my family again,” he said. “Please pray for me to go to the U.S.”

Thinking he was on his way to America, Mr. Steel Wah Doh quit his laboratory job at his refugee camp in Thailand. His father, who also hopes to be resettled in the United States, cannot get the medical checkups he needs for his immigration paperwork because camp clinics have been shut by Mr. Trump’s funding freeze.

Lifesaving American aid is supposed to be exempted from the spending ban, but health facilities remain closed. Two nonprofit representatives said they have been told that they will need to fund programs themselves before receiving reimbursements from American aid agencies. What constitutes lifesaving aid has not been made clear to them, they said.

In the Rohingya refugee camps, health clinics, learning centers and sanitation programs funded by the United States have also shut down. In one of the most densely packed places on earth, sewers are overflowing, posing the threat of disease, residents say.

Suffering from heart and kidney disease, Gul Bahar has walked through the muck to an American-funded clinic several times over the past two weeks, only to be turned away.

“I have no hope,” she said.

In Lakewood, Ohio, Mr. Steel Wah Doh’s cousin, Lay Htoo, 19, said he felt terrible for his relatives who didn’t show up as expected.

Mr. Htoo was nearly 8 when he and his family moved to the United States. He spoke no English.

His father is now a mechanic at a factory that makes gambling materials. Mr. Htoo is studying health at a community college, the first in his family to access higher education.

Now an American citizen, Mr. Htoo said he did not vote in last year’s elections. Some of the other Myanmar refugees in town, including family friends, he said, support Mr. Trump because they consider him to be a talented businessman.

“To be honest, living in those refugee camps, I remember it, and it’s not even 100 percent living,” Mr. Htoo said. “If I were still stuck there and I knew that other people voted for a guy who overturned my opportunity for a new life, I’d be extremely livid.”

Saiful Arakani contributed reporting from Teknaf, Bangladesh.