LAREDO, Texas - A few hours after dusk, three National Guard soldiers and a U.S. Border Patrol agent emerge from a hulking metal hangar in what looks like an abandoned corner of the Laredo airport and prepare for another night of hunting along the Rio Grande.
They board a lightweight Lakota helicopter, outfitted with a thermal imaging camera system so powerful they can see a man's facial expression from a thousand feet away in the dead of night. The helicopter lifts off and banks to the west, where Border Patrol agents on the ground have located a group of suspected undocumented immigrants hiding in the brush. There are 13 of them, but to the agents on the ground they are all but invisible, melting into the carrizo and mesquite.
This mission represents the latest incarnation of a once-controversial move to send National Guard soldiers to the U.S.-Mexico border to help the Border Patrol stem the tide of illegal immigration. It began in earnest in 2006 when then-President George W. Bush dispatched 6,000 National Guard soldiers to the border amid claims from critics that the move would militarize border communities and wouldn't accomplish much because the troops were prohibited from making arrests on U.S. soil.
Today, just 300 National Guard soldiers take part in the border mission, and boots on the ground have been replaced with boots in the air. Their mission consists almost entirely of nighttime helicopter flights. The flights cover most of South Texas, lifting off from Laredo and Harlingen.
But even this limited effort could be in jeopardy - not from political opposition, but from a fierce fight over resources between the National Guard and the active-duty Army, as well as uncertainty surrounding an agreement with the Department of Homeland Security to keep the mission going.
Because of budget cuts that might strip the Army of its fleet of aging Kiowa helicopters, the Army is seeking more than 100 Lakota helicopters, which conceivably could be squeezed from the National Guard, depending on what ultimately makes it into the national defense budget.
Ironically, the cuts could come as the National Guard has become more efficient than ever in finding immigrants and as illegal crossings into South Texas increase after a period of decline.
Maj. Gen. William "Len" Smith of the Texas National Guard said the budget fight could potentially hobble the border effort. If the National Guard does lose 100 Lakotas, "we'd have to commit almost all the rest of our (14) Lakotas to that mission, or stop it, neither one being preferable," he said.
The future also depends on renewal at the end of this year of an agreement between the Department of Homeland Security and the Pentagon, which some observers say isn't a slam-dunk.
As the budget fight unfolds, familiar questions over the mission's future have re-emerged: Are the millions spent along the border paying dividends? Is there still a need for a National Guard mission that eight years ago was envisioned as a temporary stopgap while the Border Patrol beefed up its resources?
There are some signs that the current, scaled-back version has been far more productive than any of its costlier predecessors.
In 2010, President Barack Obama reactivated the border mission, ordering 1,200 National Guard troops to help patrol the border. In Texas, those troops helped apprehend about 4,000 immigrants over 18 months. But in the first 18 months of the airborne mission, which replaced the ground mission in March 2012, the National Guard is credited with helping apprehend 10 times as many.
The current version also costs less than the 2010-12 incarnation: $35 million last year, down from $110 million, according to state and federal officials. That's a far cry from the $1.3 billion spent in 2006 and 2007 when the National Guard presence was at its peak.
Complaints of militarizing the border have diminished as well: The current mission is far less conspicuous than having thousands of uniformed soldiers on the ground or stationed in observation posts.
But border dynamics have also evolved considerably since 2006, with more agents patrolling what is overall a less busy border. In 2006, apprehensions along the southwestern border topped 1 million, with 12,349 Border Patrol agents on staff.
By 2013, apprehensions had fallen 61 percent, to 414,000. Meanwhile, staffing increased 73 percent to 21,391. The staffing increase has mirrored a sharp surge in spending; the department's budget grew 62 percent, to $3.4 billion, between 2006 and 2013.
The exception to the decrease, however, has been South Texas, which has become the latest hot spot for illegal crossings. In a phenomenon that agents liken to "whack-a-mole," much of the traffic that made Arizona ground zero for the Border Patrol in recent years has shifted to the Rio Grande Valley and Laredo areas. Last year, more immigrants were caught in the Rio Grande Valley sector than anywhere else along the border, a reversal from 2006 when the Tucson, Arizona, sector had more than three times as many apprehensions as the Valley.
South Texas has grown even busier in 2014, with the Homeland Security Department recently declaring a crisis in the Rio Grande Valley because of a flood of Central American immigrants and children. Overwhelmed agents have been forced to send the influx to less busy sectors in Arizona and West Texas for processing and to find emergency housing for kids at Lackland Air Force base in San Antonio.
Authorities haven't pinpointed a single cause that's driving the exodus from Central America, besides the usual suspects of poverty, gang violence, political instability and rumors of asylum and impending immigration reform.
So what does this all mean for the National Guard? According to one congressional staffer familiar with border security funding, but not authorized to speak publicly about the subject, the National Guard was always intended to be "a short-term gap filler, not a long-term arrangement."
The Homeland Security Department "needs to build the capacity to provide the aviation support that (the National Guard) presently does," the staffer said.
Observers also worry about the ever-evolving nature of the National Guard border mission and the lack of a coherent, long-term strategy at the border. The federal Government Accountability Office concluded in 2012 that the Guard's temporary status makes planning difficult for civilian authorities.
The National Guard has nine helicopters that fly from dusk until dawn in the Laredo and Rio Grande Valley sectors. In Laredo, the Border Patrol has five helicopters, which also have night vision capabilities, Border Patrol public affairs supervisor Berin Salas said. Border Patrol cameras outfitted with night vision capabilities cover about 40 miles of the river, he said.
Texas National Guard officials are hoping to have the mission enshrined as part of a strategic border plan. "Make this a more long-term program, a more planned, budgeted program," Maj. Gen. Smith said. "Those that don't agree say, 'Let's buy helicopters for Border Patrol so they can do the same mission.' One, we already have them, so why buy more? And two, it's great training for our pilots."
The effort also puts minimal strain on the Texas National Guard: With more than a dozen states aiding the effort, about 30 Texas soldiers are working on the mission at any given time. The Texas National Guard also takes part in a separate counterdrug mission, part of which occurs along the border.
Tony Payan, a border security expert at Rice University, said that more than National Guard soldiers, the border needs additional clerks and administrators to process the children and Central American immigrants swamping the Border Patrol in South Texas.
"This is not a war scenario," he said. "Border Patrol has more than enough hands and feet on the ground to do the job, and they should do it."
But local Border Patrol agents say they have no desire to see the National Guard leave the border. "It's a comfort to know these guys are observing from the air, like a safety net," said assistant chief patrol agent Dan Ramos. "The amount of assistance is invaluable. They have provided us an extra level of safety."