Active-duty troops are now at the U.S. border with Mexico, two weeks after President Trump ordered the deployment in response to a large group of migrants headed north from Central America.
A few feet away from the U.S./Mexico border in Donna, Texas, troops have built what appears to be an encampment.
Rows of square green tents, several shipping containers, and an unfinished steel frame structure are visible from the road near the Donna Río Bravo International Bridge, which connects Texas to the Mexican state of Tamaulipas. Uniformed military personnel stand watch behind a razor wire barrier. Sand-colored military vehicles and U.S. Customs and Border Patrol trucks rumble in and out at regular intervals.
About 20 miles west, people crossing at the McAllen-Hidalgo port of entry have noticed concertina wire on the riverbank and the international bridge. Locals have seen U.S. troops conducting drills.
"They've been doing simulations," said Eba Altubarz, speaking through an interpreter. "They get formed up, lined up, and they're going through the drills. But I don't know exactly what they're doing, as far as exercises are concerned."
Altubarz, a Mexican citizen, lives directly across the bridge in Reynosa. She crosses once or twice a week to go shopping. With the growing number of migrants waiting to cross the border, coupled with the troops' arrival, Altubarz said she's concerned about the possibility of conflict.
"I'm really worried, so I'm watching TV to see what's going on," she said. "I'm worried about violence."
But Roberto Ruiz, another Reynosa resident, said he views the troops as a stabilizing presence.
"I think it's good because we have a lot of people coming from Central America and a lot of people that come with gangs," he said. We have problems with them. There's going to be problems in Mexico."
In neighboring Texas towns like Weslaco, some Americans also welcome the troops, whom they've noticed on the roads, at the local airport, and on TV.
Thelma Anciso has children in the military and said she feels calmer knowing that active-duty soldiers are patrolling the ports.
"They're protecting us. It feels good. I feel secure with them here. I pray for them every day," she said.
According to Mike Seifert of the ACLU, who lives in Brownsville, many border residents assume the troops are there because of a pressing threat - one which, he said, doesn't really exist.
"Where there's smoke, there's got to be fire," he said.
Seifert says some of his fellow activists conducted a survey in the Texas border town of Edinburg.
"Essentially the question was: 'Do you feel safe?' And the response a lot of the time was, 'No.' And why is that? 'Have you been witness to or a victim of a crime?' And they were like 'No, no, no,' " he said. "But we see so many troops and police and border patrol, something must be going on.'"
A handful of activist groups in McAllen have been protesting what they call the "militarization of the border." Scott Nicol, co-chair of the Sierra Club Borderlands Team, said the deployment is a political stunt designed to whip up fear.
"You have helicopter landings. You have troops in riot gear marching across the bridge. That's all being done, I think, for show," he said. "They have an audience of one in the White House who has said that he thinks the concertina wire looks beautiful. Honestly, I think that this whole deployment is a fairly despicable show."
Pentagon officials have said the active-duty troops will work to support Border Patrol with planning, engineering, transportation and medical teams, and that they will not have direct contact with migrants crossing the border.
Five public affairs units have also been deployed to distribute photos and video.
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.