— The three soldiers in the Maryland National Guard helicopter crew lifted off from this sweltering border city shortly after sunset, with a federal agent on board and three "tickets" — reports of persons attempting to slip across the Rio Grande from Mexico into the United States.
They spent an hour sweeping the river with infrared and night vision, but saw only Border Patrol agents, in their white SUVs or on foot, along the northern bank of the shallow river that separates the two countries. The Maryland crew chief, watching a glowing computer monitor inside the UH-72a Lakota helicopter, toggled through screen after screen in search of migrants.
Finally, a hit: the ghostly images of three adults wading north across the river. Then, a group of 11 or 12 fording a different stretch of the slow-moving waterway. And three more, sitting on the American side of the river, their feet still in the water — ready, if challenged, to cross back to Mexico.
"I was amazed at how many people cross the border each and every night," said Chief Warrant Officer 4 Scott Sauer, a Maryland Guard pilot who has served two deployments here. "And how unsecure our borders truly are."
That volume of traffic has brought the Marylanders to the busiest stretch of the Southwest border to bolster federal enforcement efforts.
Elsewhere on the 2,000-mile frontier, government statistics suggest a decade-long decline in attempted crossings. But in the Border Patrol sectors of Laredo and the Rio Grande Valley in South Texas, the number of apprehensions has exploded, from 95,000 in fiscal year 2011 to 205,000 last year.
Border Patrol agents here say increasingly aggressive criminal organizations — in many cases, the same ones that smuggle drugs — are responsible for the ever-growing number of immigrants in the country without legal documents. Last year, South Texas surpassed Arizona as the principal crossing for unauthorized entrants.
"We're getting slammed," said Agent Chris Cabrera, a leader of the Border Patrol union in the Rio Grande Valley. "We're getting overrun down here."
Maryland is one of several states that have answered a call for help. Since January, crews from the Edgewood-based 1-224th Aviation Security and Support Battalion have flown night surveillance missions to spot unauthorized crossers and to guide agents through the thorny scrub to their hiding places. It's the battalion's second deployment to the area in the last two years.
Border Patrol officials say it's making a difference. They credit Guard crews with spotting more than 6,500 people during the first three months of the year, helping to apprehend nearly 5,300 and turning another 850 back across the border.
"Now we have eyes in the sky," said Peter Ayala, a Border Patrol supervisor in Laredo. "They can run, but we still can see where they're going. So we don't have to be endangering ourselves or the public when we're out there. … You can see in a couple of years the tremendous effect that they've had."
Cabrera concurred: "Those guys are friggin' awesome."
Maj. Gen. James Adkins, the commander of the Maryland National Guard, says the state's air crews are keeping their skills sharp as they help enforce the border, protect property and save lives.
"It's kind of a natural mission for us," he said. "Whether in blizzards or in hurricanes, our focus has always been to support somebody else so they can do their job. If we can help the Border Patrol do their job, that's all good for the nation."
The effort has drawn some criticism. Gustavo Andrade, organizing director of CASA de Maryland, said he was surprised that Gov. Martin O'Malley approved Maryland's participation.
"That policy seems inconsistent with Maryland's values of upholding immigrants' rights," Andrade said.
He pointed to state legislation in recent years that has allowed immigrants without legal documentation to attend public colleges and universities in Maryland at in-state tuition rates and to get driver's licenses. He also noted O'Malley's announcement this month that the state would no longer automatically honor requests from U.S. Immigration and Customs Enforcement to hold arrested immigrants in the Baltimore jail beyond the point when they ordinarily would be released.
"We would hope that Maryland's mission on the border is purely humanitarian," Andrade said.
O'Malley, who as governor is commander-in-chief of the Maryland National Guard, said in a statement that Guard members may be activated to serve in a variety of missions, from responding to natural disasters at home to supporting peacekeeping efforts overseas. "Members of the Maryland National Guard who are serving on the United States-Mexico border are supporting federal missions," he said.
The American Civil Liberties Union, meanwhile, has warned of the increasing militarization of the border. With Guard helicopters, surveillance blimps and drones in the sky, ACLU of Texas director Terri Burke expressed concern about the privacy of property owners and others along the border.
"Is this the highest and best use of our military resources?" she asked.
Susan Kibbe, the director of a property owners association based in the Rio Grande Valley, says the ranchers and farmers she represents welcome stronger border enforcement.
"The landowner, for the most part, is in support of anything that maintains law and order," she said. "They appreciate the help. They've asked for it."
The South Texans' Property Rights Association comprises some 600 members, who own 5 million acres on or near the border, according to Kibbe. She says they face intimidation from smugglers and damage to their property.
"In some areas, it's a real feeling of lawlessness," she said.
There is no way of knowing how many people succeed in entering the country illegally. In Laredo, an individual who makes it across the river undetected may disappear into the large local Latino community. Or he or she might jump into a car waiting on U.S. 83 — which runs parallel to, and in some places just a few hundred feet from, the border — and head elsewhere.
Officials and analysts use the number of immigrants who are apprehended as a rough indicator of how many are attempting to enter the country. Here, South Texas leads the nation. While apprehensions elsewhere along the border declined by 10 percent during the last three years, in Laredo and the Rio Grande Valley they more than doubled.
The largest group is Central Americans, for whom the southern tip of Texas is the closest point of entry into the United States. Officials, advocates and observers say the immigrants come principally for jobs and to reunite with family. The volume of traffic tends to ebb and flow with the economy in the United States and conditions in the immigrants' countries of origin.
The current boom in South Texas has come despite increased enforcement. It is expected that the immigration overhaul long sought by advocates on all sides will include a requirement that the borders be secured. But with legislation stalled in Congress, the Obama administration has moved unilaterally to deploy more personnel and technology to the border.
Edward Alden, a senior fellow of the Council on Foreign Relations who has studied illegal immigration, says the buildup has had an impact.
"We know that a higher percentage of people are being caught," said Alden, who co-authored the 2013 council report "Managing Illegal Immigration to the United States." "We know that the consequences for being caught are much more severe than they used to be. There is some evidence from surveys on the Mexican side of the border that the enforcement is having a deterrent effect."
The improved enforcement has had a perverse result: As it has grown more difficult to enter the country illegally, immigrants have turned increasingly to criminal organizations to take them across the border. The going rate for a crossing is in the thousands of dollars. Narcotraffickers such as the Zetas and the Sinaloa Cartel now dominate the business.
"The days of the mom-and-pop, 'Let me just jump the border and see what happens' — that doesn't happen anymore," said Manuel Martinez, an assistant chief of the Border Patrol Laredo Sector. "Everything is controlled on the Mexican side. They dictate who comes across."
Martinez says this leaves the immigrants vulnerable to criminals, who rarely warn their clients of the dangers of the desert, what to wear or how much water they'll need.
"A lot of these people, they're told, 'Jump in, we're going to have a little quick 20-minute walk, we'll go around and we're done,' " he said. "Next thing you know, they're on a three-day hike."
The Border Patrol counted 212 deaths last year in Laredo and the Rio Grande Valley, many from exposure or dehydration. That's nearly half the 445 recorded along the length of the Southwest border.
Cabrera, the union leader, says the National Guard helicopters have been invaluable in anticipating immigrants in distress and enabling rescues.
"From that height, they can see into Mexico," he said. "When there's somebody drowning in the river, they can coordinate. People that are lost in the woods."
Lights in the night
The Maryland guard's history on the border dates to 1917, when members were deployed to Eagle Pass, Texas, as units from that state entered Mexico to hunt for revolutionary leader Pancho Villa. More recently, Marylanders went to Arizona in 2006 to man observation posts in support of the Border Patrol.
In 2012, the 1-224th Aviation Security and Support Battalion deployed to Harlingen, Texas, in the Rio Grande Valley for Operation River Watch II, the current mission. Flying two of their then-new Lakota helicopters, crews helped spot nearly 2,000 illegal crossings during one five-month period. They helped to apprehend nearly 1,300 suspects, turn back more than 300 and seize drugs with a street value that officials estimated at nearly $5 million.
Members of the 1-224th, which also flies missions in Maryland with the state police and the Secret Service, returned to Texas in January. They now split their time between Laredo and Harlingen.
"That's what the battalion is designed to do," said Maj. Kirk Regina, acting commander of the unit. "Support homeland defense, homeland security."
The Maryland crew gathered at an operations center at Laredo International Airport one evening this month for a preflight briefing. They included two pilots and a crew chief, with a Border Patrol agent. As a condition of flying with the crew, The Baltimore Sun agreed not to publish their names.
"There is the aspect of surveillance and counter-surveillance that takes place when we're working along the border," said Sauer, who left Texas last year. "They have guys there that pretty much watch when you take off, trying to figure out which way you're going. … Guys do get followed."
During the afternoon, the temperature rose above 100 degrees; by the time the crew lifted off, it had retreated to the 80s. From a few thousand feet up, Laredo and its Mexican neighbor, Nuevo Laredo, appear to be a single city, with a river running through the center.
Using an encrypted frequency, the Border Patrol agent received three tickets from a dispatcher on the ground. One group of nine or 10 people had been spotted crossing the river at the Dairy, a ranch in Laredo South. Two more groups were reported near Zapata, south of Laredo.
The pilots guided the helicopter south along the river. As the Border Patrol agent took directions over the radio, the crew chief used an infrared camera under the nose of the aircraft to bring up images of the ground on the computer monitor.
He spotted agents on the U.S. side, fishermen on the "Mike side" — the Mexican bank — and, finally, people crossing the river. The crew watched as men and women, apparently unaware they had been seen, clambered onto American land, entered the scrub and huddled together. The video was also relayed to the Border Patrol on the ground.
The crew chief aimed a laser at the group. The light was invisible to the naked eye, but anyone wearing night-vision goggles could see the "Finger of God": a thin green line, running straight from the helicopter to the immigrants, giving their location away. Two Border Patrol agents on the ground closed in.
Later, the agent in the helicopter would use a different kind of light — a 43 million-candlepower Nightsun spotlight — to illuminate a group of crossers and turn them back over the border.
Cabrera said the aerial surveillance gives confidence to agents on the ground.
"It's not uncommon for a group of Border Patrol agents, two or three guys, to apprehend 60, 70 people," he said. "When you have the eyes up there watching to see if there's anything coming on your back side, to be able to warn you, that helps."
Alden of the Council on Foreign Relations and his co-authors estimated that 40 percent to 55 percent of those who attempt to cross the Southwest border illegally are apprehended. Participants in the debate over immigration overhaul have spoken of achieving a 90 percent effectiveness rate. That would include both apprehensions and immigrants turned back.
"You're never going to get to zero," Alden said. "The border between East and West Germany — so, you know, barbed wire, quarter-mile-long no-man's land, floodlights, shoot-to-kill orders, et cetera, et cetera — a thousand people a year managed to get across that border."
Sauer is looking forward to returning to the Texas border later this year.
"I have a lot of compassion for the [agents] that are out there in the woods, basically out there by themselves," he said. "Having the open borders that we have ... you don't really know what's coming across, whether it be narcotics or the people.
"A lot of people think it's just solely people from Mexico. But if you talk to the agents on the ground, if you go to the holding facilities, you'll see that they have people from all over the world, whether it be China, Russia, Africa. I mean, all these people who kind of filter their way up, and you just never know who's coming across the border."
Baltimore Sun reporters Erin Cox and Justin George contributed to this article.