HIDALGO COUNTY, N.M. » A white pickup truck rumbled along the barbed-wire fence that divides the United States and Mexico, toward a crude gate nicknamed Mingas, carved by drug smugglers to bring their supply across the border.

On U.S. soil, Daniel Algarate Martinez, a Border Patrol agent, gripped his rifle, staring at the truck that approached on the other side of the divide. A coyote howled in the distance. The truck, loaded with logs, raced past him, past Mingas, and kept on going.

"I wonder what he has under that wood," Algarate Martinez mumbled.

The path to the Mingas gate is a circuitous and sorry dirt trail of unpredictable dangers, brought by the desert, the remoteness and the illicit drug trade. It is on the eastern edge of the Bootheel in New Mexico’s southwest corner, where the border juts down and Mexico stands briefly to America’s east, one of the most remote spots in the roughly 2,000 miles where the countries intersect.

The closest Border Patrol station is about 60 miles away, an eternity in a region where most roads were cut by ranchers’ tractors and cattle hooves. The closest agents are much closer these days, though, stationed for days in outposts deep in the Chihuahuan desert, so close to Mexico that the lights of its farms are the often the only noticeable sign of human life.

The agents sleep in bunk beds, sharing meals in a communal kitchen next to lounges where TV sets are perennially tuned in to ESPN. Water comes from wells. Diesel tanks hold fuel for the vehicles. Dormitories, command centers and holding cells occupy modular buildings encircled by floodlights and chain-link fences, a setup modeled after the military’s forward-operating bases in Afghanistan.

Ramiro E. Cordero, a special-operations supervisor for the Border Patrol’s El Paso sector, which is responsible for 268 miles of borderland, including the Bootheel, said the bases were an essential element in the agency’s quasi-military strategy of "gaining, maintaining and expanding." They provide a presence in isolated areas where building brick-and-mortar stations would have been impractical.

There are two of them in New Mexico, on the eastern and western flanks of the Bootheel. Camp Ramsey, where Algarate Martinez is sometimes stationed, opened in 2009. Camp Garza opened in November — the ripple effect of a rancher’s killing in Arizona, most likely by a drug smuggler.

Though the number of apprehensions of illegal border crossers has continued its steady decline, the number of drug seizures has remained constant all along the American Southwest, according to a report by the Government Accountability Office, justifying the Border Patrol’s expansion into such remote areas. Arizona has five such forward-operating bases with three more to open this year.

In the El Paso sector, the number of detained illegal immigrants fell to roughly 10,400 last year from 122,000 in 2006. Cordero said half of them were captured in the Bootheel region, where, unless a migrant got lost while trying to sneak into the United States through Arizona, the people who get caught are likely to be carrying bundles of marijuana.

Dispassionately, Algarate Martinez, 37, who is from Zaragoza, Spain, said, "This is dope country."

There are four to six agents assigned to each shift at Camp Ramsey: morning, swing and midnight. They each stay there for five days and five nights, and they each patrol alone, looking for signs of people where people are not expected to be.

It seems like an exercise in futility — agents scanning the rocky, dusty ground for human footprints amid the footprints of cows, bobcats, wild pigs and mountain lions from inside their Ford Raptors, but mostly by foot.

Algarate Martinez drove to Mingas to check on sensors that had been tripped in sequence, following the type of northward pattern typically traveled by smugglers. He found no one and figured it must have been a false alarm, which is not uncommon.

Dinner at Camp Ramsey that night was burgers cooked on the grill by one of the agents; he dropped a plate of them on the communal table, and then shuffled to his bed to catch some sleep before his shift began at midnight.

The agents bring their own food — Doritos chips, chocolate-chip granola bars, spicy kung pao noodles ("just add hot water") and Lean Cuisine. Aaron Dozal, 25, who is from El Paso, seasoned his burger with a pungent green-chili sauce his wife had made for him.

An agent working overnight captured two drug mules somewhere between the Mingas gate and Monument 40, an obelisk-shaped border marker so white it glows in the dark when the full moon is out. The shift’s supervisor told the five agents reporting to work in the morning that two other mules had gotten away.

One of those agents, Luis Colon Diaz, who is 32 and from Puerto Rico, decided he would carry out his search on foot, on the hills behind an abandoned yellow house in the Victorio Ranch, a rambling property speckled by hideouts used by spotters for the drug gangs. The trek consisted of roughly four miles in a circular pattern across a succession of hills. It had rained hard overnight, which was at once bad and good: bad because it might have washed away footprints, and good because new footprints would be easy to spot on the moist ground.

The first out-of-place thing he found was a water bottle, which still had beads of water inside. "Fresh," Colon Diaz said. He adjusted the strap that held his shotgun over his shoulder, as if to make sure the weapon was still there.

He has a degree in anthropology from the University of Colorado, Denver, where he once wrote a paper comparing the digestive systems of cows and howler monkeys.

On top of some rocks at the crest of a hill, he found a blue toothbrush. There was a bit of shade from a bush and a clear view of the U.S. side of the border, as far as Interstate 10. Undeniably, he said, "a spotter’s hangout."

The radio crackled. Another agent moving in the area said, "Looks like there’s one on one side of the water tank by the ravine and another guy on the other side."

Colon Diaz took his shotgun off his shoulder and aimed it forward as he made his way down the hill, following an arroyo that he knew led to the water tank.

"Animals," said the voice on the radio.

Distant sights are deceiving in the desert. Cows can seem like humans moving slowly through thorny brush.

Back at his truck, Colon Diaz unloaded his shotgun and drove to Camp Ramsey, the end of another shift.

In a busy urban area, he said, "an agent has minutes" to figure out where an illegal border-crosser is going and catch him before he gets away.

The Bootheel is so far from everything, he went on, "it’s going to be hours, days, until these guys get anywhere. I’ve got time."