ARRIAGA, Mexico >> The police truck appeared suddenly, a glint of metal and glass. The migrants broke into a sprint, tripping over cracked pavement as an older woman sweeping her stoop urged them to hurry.

The 10 men rounded the corner and hid behind a row of low-slung trees. Four days into their journey from Central America, the new reality on Mexico’s southern border was setting in: Under pressure from the United States, the Mexican authorities were cracking down.

Minutes passed. The men fanned out and doubled over to catch their breath. Along the tree line, a man approached in flip-flops and a collared shirt. He told them not to worry — he knew the way north.

Small, with jaundiced eyes, he was practiced in the art of smuggling. He could spot patrols, flag down vehicles for rides, even navigate the hidden trails carved into the lush countryside. They could trust him, he promised. He just wanted to help.

At first, they barely acknowledged him. But the more he talked, the harder he became to ignore. What was the alternative? It came down to going with him or going it alone, back into unfamiliar streets brimming with the Mexican authorities.

It was a migrant’s choice: Weigh the risks of pushing forward against the prospect of going home. The men — six Hondurans and four Guatemalans — reluctantly agreed.

“There are two kinds of stories on this trip,” said one of the men, Rafael Lesveri Pérez, a 38-year-old Guatemalan and three-time veteran of the journey, shouldering his bag as the group prepared to set off with the smuggler. “There are the true ones, and there are lies. Only time tells which is which.”

A Dragnet Awaits

The next two days were a microcosm of the passage north for Central American migrants, a trip that has grown increasingly dangerous in the wake of the Mexican crackdown.

Fleeing a surge in gang violence and a void of opportunity, record numbers of Central Americans began streaming toward the United States in the spring of 2014. That year, 68,631 children, nearly twice as many as in the previous year, were stopped at the U.S. border, having chosen the risks of the 1,000-mile journey over the dangers they faced back home.

To stem the flow, the White House promised aid to help build better lives for the migrants in their own countries. In December, $750 million was approved for Guatemala, Honduras and El Salvador.

But the Obama administration took other steps, too, pressing the Mexicans to tighten their borders and to create what amounts to a migrant dragnet hundreds of miles south of the United States.

Plan Frontera Sur, as the Mexican government’s campaign is called, serves as a first line of defense for the United States. Deportations have soared in the last year, while the arrests of Central American migrants in this country have more than doubled, from about 78,000 in 2013 to more than 170,000 last year.

For all the effort, the Mexican campaign has not deterred the migrants. Instead, what was already a treacherous journey has become even more dangerous.

The enhanced vigilance of the Mexican authorities has forced migrants to abandon trains and buses in favor of riskier routes on foot through remote stretches of the Mexican countryside crawling with gangs, frustrated villagers and corrupt police officers.

Officials and rights advocates in the southern states of Chiapas, Tabasco and Oaxaca report an increase in violence against migrants — and not just at the hands of criminals. The National Human Rights Commission of Mexico reported a 40 percent increase in migrant complaints against the authorities in the year after the plan took effect.

The sustained presence of migrants has also frayed the patience of many Mexicans. Traveling on foot, the migrants are staying longer in communities they once bypassed by train, stirring resentment and fear among a populace unaccustomed to outsiders. Violence by residents has grown more common. Some communities have signed petitions demanding the removal of migrant shelters.

Over two days in early November, the 10 migrants here in Arriaga, in Chiapas state, would trek more than 40 miles across dense forests, sun-bleached farmland and highways patrolled by the authorities, terrain so unforgiving that some of their shoes fell apart. A journey of 30 minutes by car required more than 20 hours of walking.

They would spend a sleepless night on a concrete porch, bracing themselves for the hostile residents of a village to attack. One would fall gravely ill, splitting the group and threatening to end the journey. Only two of the men would make it to the United States.

Almost nothing the smuggler promised would come to pass.

Into a Smuggler’s Arms

The route through Mexico used to be more straightforward. Many migrants took the Beast, the nickname for a cargo train that was long an integral part of the journey to America. But train passage through the south of Mexico has been drastically reduced as the authorities have increased surveillance.

That vigilance nearly ended the men’s journey before it began. On the morning of their departure, the migrants had been warned by a friendly local to get moving from an area near the tracks. Immigration agents would be passing through. Moments later, a police truck appeared, pushing the men into the arms of the smuggler.

Step by step, he outlined his plan for the migrants’ trip, a combination of vehicle and foot transport that would take them 100 miles in two days. The cost: just $15 a man.

Walter Martínez, 28, the leader among the Hondurans, plucked a cardboard pillbox from his book bag and opened it along the seams. The Hondurans were prepared and experienced. Written on the inside of the makeshift document were the names of cities along the route. This, according to his document, was “Part 1.”

He pressed the smuggler for details. The man complied: They would rely on a network of drivers to shuttle them from checkpoint to checkpoint. They would get out only to walk around the government barriers.

But first, he said, they had to go to his home. He needed shoes.

“You will see, I’m just like you guys,” he told the men as they made their way along a rise and back to the road. “I was also a migrant.”

Trudging in Hostile Lands

The journey he laid out is among the most dangerous for those on foot. Local officials say the number of assaults on this remote stretch has doubled in the last year. Theft, assault and rape are common. Small votives, memorials to the dead, flicker beneath trees along the way.

But the biggest challenge the migrants would face came from within the group itself.

Josué Carillas Carnelas, a 30-year-old Honduran who had lived in Colorado until being deported, fell ill, vomiting along the roadside as the men started the walk. The men, suspecting it was from drinking water from a puddle a day earlier, urged him along with the prospect of a minivan.

There was none. Neither the smuggler’s contacts nor his “intimate” knowledge of the transport system yielded a ride. At every station, the men accepted this with poise and kept walking. The landscape took them through dense jungle and open fields. Undulating mountains were sketched along the sky’s edge.

Three of the Guatemalans had never left home before. They stayed near the front, as if proving something to the others. The eldest, a 50-year-old laborer named Negrole Jorgito López, was especially eager. The night before, at a shelter, the younger men called him Grandpa.

‘This Isn’t a Safe Place’

The village of Emiliano Zapata, named after the Mexican Revolution hero, hugged a small road off the highway — a grid of pastel-colored homes, their doors thrown open to the night.

The smuggler promised they would make it twice as far as they had the first day, but after seven hours of walking, the men were muted by their fatigue. No one registered a complaint, or even bothered to hide, as they entered the village.

The smuggler told them his brother lived in the village and would put them up for the night. He had food, too, for a modest cost. The men nodded, passing a smashed concrete roundabout where a group of locals sat, drinking.

“What do you want here, mojados?” one of them yelled, using the Spanish equivalent of “wetbacks,” an irony apparently lost on the local in a country that has sent countless migrants north. The migrants snapped to attention. Another local yelled an expletive. A third beckoned them with taunts.

Martínez, the Honduran who had become the group’s de facto leader, told everyone to keep moving. “Don’t turn around,” he whispered.

The smuggler raced ahead and ushered the group into an unlit house a few blocks from the roundabout. Across the street, three women sat on a stoop watching.

One of them beckoned to Lesveri.

“This isn’t a safe place,” she whispered, leaning forward in her chair. “Migrants get attacked and even killed in that house.”

Shaking, he raced into the backyard of the home, where the others were sprawled on a porch. The smuggler was busy selling them a dinner of fried eggs for a few dollars apiece.

Lesveri grabbed him.

“Where the hell have you brought us?” he demanded.

Almost no one slept that night.

At 3:30 a.m., their morning ritual began. They washed their faces and plucked their shirts and socks from a clothesline. Someone produced a tub of hair gel, and each man took turns styling himself. Martínez sang love songs off-key while the others laughed.

They formed a circle and prayed, a solemn two minutes to cap a difficult night. They prayed for safety, good fortune and a future in America, then left under cover of darkness. They seemed to trust the smuggler more, now that the worst had passed.

‘Migra!’

The next crisis came quickly. After they crossed a series of highways, careening down the opposite banks into all-but-impenetrable foliage, Carillas collapsed. The others placed him on a large stone and took turns fanning him, his face a swollen red and his breathing labored.

He closed his eyes and nearly fell from his perch.

“I can’t keep going,” he said.

Getting him help might have meant the end of their journey. The youngest among them was instructed to accompany the sick man to a hospital while the rest pushed on. He nodded without complaint. Just ahead, the highway passed over the railway tracks, a literal crossroads.

The men scrambled up the side of the underpass, sliding along the steep concrete slope as they lifted Carillas by his arms. They huddled in the shade of the bridge as the smuggler stood on the highway’s guardrail, looking for a taxi.

Over the drone of midday traffic, he began yelling.

“Migra!” he screamed, using slang for the immigration authorities.

The flight down the underside of the bridge was sloppy, dangerous. Carillas, unable to rouse himself, stayed behind while the others tumbled into a ravine.

When the authorities did not storm the bridge, the migrants made their way back up, all except López, the oldest. He raced down the footpath they had followed, alone.

“I’m going ahead,” he yelled to the group. “I can’t wait here to be caught.”

His two novice companions raced after him.

By the time they hailed a taxi, Martínez, the group leader, decided to accompany Carillas himself in the taxi to the hospital. The two climbed over the guardrail and vanished, and the smuggler watched the taxi depart with a deep sigh.

Two more shares of his income gone.

The walk continued in the blazing sun. If there was a silver lining in the oppressive heat, it was that the Guatemalans who had raced ahead were moving slowly now, pausing often to rest and, for one of them, to repair the sole of a shoe.

Reaching the small town of Chahuites in southwestern Mexico became an object of obsession for them. At every stop, someone would ask the smuggler how much farther they had to go. They fantasized about lunch, a large bottle of soda, new shoes.

But Chahuites was hardly as welcoming as it had been. It was now a symbol of the changes along the route north. A church-run migrant shelter, opened a year earlier, was under threat from fed-up citizens, who had filed a petition for its removal.

“I know our people are right for being upset, but immigrants have rights, too,” said José Antonio Ruiz Santos, the mayor of Chahuites.

As they entered the city, the men found Martínez sitting on a fence, waiting for them in the shade. He offered a smile and an update — he and Carillas had made it safely.

He led them to the migrant shelter, where Carillas was resting, the happy recipient of pills and an intravenous drip without having been reported to the immigration authorities. Outside, tattooed men played soccer in the streets. Others smoked cigarettes by the entrance.

“Let’s keep moving,” Martínez told the group.

© 2016 The New York Times Company