During the eight months they've been deployed at the U.S.-Mexico border, military personnel have had little direct contact with the people at the center of the mission.
Soldiers and Marines are stretched along the U.S. southern border from California to Texas. Among the tasks they've performed: monitoring surveillance cameras, installing concertina wire, and painting border barriers.
But they rarely come in contact with migrants who cross the border from Mexico.
"We are not taught to engage in this particular mission set," says Lt. Col. Timothy Gatlin, the commander of 1st Battalion, 37th Field Artillery Regiment. "We want to de-escalate every situation we come in contact with and turn it over to the supported element, which is the Border Patrol."
Soldiers from Joint Base Lewis McChord near Tacoma, Wash. are stationed around El Paso. They've been drilled on the rules of force when working with Border Patrol. Customs and Border Protection trained them for about 40 hours on the equipment the agency uses and how to react when someone approaches, Gatlin said.
"Training that we got before and during the mission really just tells us we want to be able to back away from any engagement and get on the BP radio and radio to our BP partners."
Soldiers carry flashcards in Spanish to communicate with asylum seekers and other migrants. Troops mainly encounter people who are looking for water or who want to turn themselves into the Border Patrol, said Col. Paul Nathan Garcia, deputy commander of Joint Task Force North, which is in charge of the operation.
"I would say across the entire southwest border, we’ll have one or two (encounters) that happen," he said. "I’m talking 2,000 miles of southwest border, 150 sites, that we’ll mainly have a couple a week."
A handful of more serious encounters have been made public. In April, members of the Mexican military stopped and questioned two U.S. soldiers in an unmarked CBP vehicle near Clint, Tex. A CBP and Pentagon review found the Mexican troops mistakenly believed the soldiers were south of the Mexican border, said Col. Cathy Wilkinson, a spokeswoman for the border mission.
In May, two service members assigned to the Defense Department’s Southwest Border Support mission were involved in the negligent discharge of a military-issued handgun during mobile surveillance camera operations in Yuma, Az. One person received injuries that were not life-threatening and was treated at a civilian hospital. The incident is under investigation, Wilkinson said.
On May 19, soldiers reported someone pointed a gun at them. CBP responded with the Yuma County Sheriff's Office and apprehended the suspects, Wilkinson said.
Also, a Marine discharged his weapon May 29 while stationed at a mobile surveillance site near El Centro, Cal. An investigation is ongoing, she said.
Brig. Gen. Walter Duzzny, the Deputy Commanding General of U.S. Army North, says contact between troops and migrants is infrequent.
"It is very uncommon," he said, "especially for the duration of the operation and really the size of the operation, in terms of the geographic size of the border, it's extremely small."
Since they first arrived at the border in October, troops have mostly performed missions that keep them away from anyone crossing the border. Soldiers and Marines laid miles of concertina wire and erected barriers at the ports of entry. Troops have aided in the apprehension of 13,000 people and the seizure of 3,000 pounds of marijuana.
The numbers are small compared to the traffic coming across the southern border. CBP released figures showing 593,507 migrants have been taken into custody since the beginning of the year. The agency takes in roughly 5,863 pounds of narcotics a day on average.
By working surveillance and other missions along the border, troops are freeing up border agents to take a more active role, Duzzny said.
In El Paso -- a city heavily dependent on trade with Mexico -- every aspect of border policy draws attention. But the military's presence has barely registered with many residents. The city is home to Fort Bliss and is accustomed to military operations.
At Los Bandidos De Carlos and Mickeys, a busy Mexican restaurant, some of the customers wear Army uniforms. Owner Rosa Saenz is one of several restauranteurs who deliver food to asylum seekers dropped off by Border Patrol. She says there are a lot of problems related to the way migrants are being handled, but so far, she says most people don't blame the military.
"In El Paso, we understand what the military is about," Saenz said. "We don't blame them. We know they're following orders. They're doing their jobs. How you follow orders, of course, you know, you can either do it with a certain amount of assertiveness or you can do it with the understanding that these are just people."
Troops could become more visible along the border. The Pentagon has agreed to begin transporting migrants to detention facilities and begin providing food service. Troops also are scheduled to build six new detention facilities, though the details of those operations haven't been released.
This story was produced by the American Homefront Project, a public media collaboration that reports on American military life and veterans. Funding comes from the Corporation for Public Broadcasting.