PROGRESO, Tex. — A helicopter circled the cloudy skies near the border Thursday morning and kicked up debris as it landed in a swirl of noise and dust.
Eight officers leapt out, dressed and poised as if for combat near the bridge that connects the United States with Mexico in the border town of Progreso. Wearing helmets, flak vests and battle fatigues, they crouched on their knees and aimed military-style rifles at various points in the distance. As a woman who had just crossed over the bridge stopped to record the scene on her cellphone, the helicopter landed again; the officers formed a line, ran inside and were gone.
The first wave of the new Army deployment President Trump has ordered at the southern border?
The helicopter and the officers were with the Border Patrol’s parent agency, Customs and Border Protection. But as thousands of soldiers prepared to deploy to South Texas and other points along the border as part of Mr. Trump’s mobilization of active-duty troops, the training drill was a sign of a new hardening of the border slowly taking shape involving multiple agencies, not just the Army.
The authorities have installed new chain-link gates and fencing on the Progreso International Bridge, near the scene of Thursday’s drill, giving officials a crowd-control tool for the first time by allowing them, when necessary, to completely shut off the bridge to cars and pedestrians coming from Mexico.
The new barriers remained open on Thursday. But the additional fencing, the military-style drills and the arrival of equipment and small groups of Army personnel in advance of an expected large contingent of troops represent a far more visible display of a militarized border than has been seen in South Texas in recent years.
Many of the details about the arrival dates and locations of the new military units remain unclear. A handful of troops have already arrived and have been spotted at and near so-called ports of entry along the Texas border, including international bridges, and thousands more have been placed on a prepare-to-deploy status. Officials have identified more than a dozen bases in Texas, California and Arizona that will serve as logistical hubs for what has been named Operation Faithful Patriot.
A total of up to 15,000 soldiers, primarily from the Army, are to provide technical and logistical support. They will be armed, but are under orders not to directly engage with migrants. Mr. Trump on Thursday said they would be authorized to defend themselves against threats, including any migrants who throw rocks.
Officials said that forces are staging at military installations for now because it is unclear precisely where on the border their main object of concern — several caravans of Central American migrants, the first of which is now in central Mexico — will head.
Mr. Trump on Thursday portrayed the caravans — which include thousands of families, many with children, hoping to escape violence and poverty in their homelands — as a threat to national security. “It’s like an invasion,” he said, of “unbelievably rough people.”
“We have already dispatched to our border the United States military,” he said. “They will do the job. They’re setting up right now.”
The presence of the military at the southern border is nothing new. Democratic and Republican presidents have ordered troops to the region in decades past. Republican leaders in Texas called up the National Guard during the Obama administration and kept them there. Hundreds of National Guard soldiers began assisting the Border Patrol in April, as part of Mr. Trump’s earlier call-up to America’s southern border.
But those actions remained largely invisible to the public in border towns and cities like Progreso, McAllen and Brownsville. When National Guard troops traveled in convoys during the president’s April mobilization, they often used rental cars and trucks, in part to soften their presence and not give residents the impression they were living in a militarized zone.
Some of that invisibility appears to be deemed less necessary now. Officials said Customs and Border Protection conducts training drills like the one that happened Thursday in Progreso a couple of times a year, but the timing and location near the border crossing seemed more than a coincidence, coming as it did on the very day that Mr. Trump was describing a toughened strategy for detaining migrants and processing asylum claims.
“We’re going to see a beating of the chest in terms of American military might,” said Representative Filemon B. Vela Jr., a Brownsville Democrat whose congressional district includes the area of the training drill. “The orders are coming from the top, straight from the president himself, so these guys serve at the service of the president. It’s an election scam.”
Mr. Vela said sending active-duty Army troops to the border was a misguided and costly use of the military, and that Mr. Trump’s recent deployment of the National Guard illustrated why.
“I was at a groundbreaking for a bridge in Brownsville two months ago, and I finally saw the National Guard,” Mr. Vela said. “Do you know what they were doing? They were handing out water and they were helping people park. I hadn’t seen them before that moment and I haven’t seen them since.”
Even though the migrants in the caravan are still weeks away from the border, officials in South Texas have been busy preparing for their arrival.
Last week, the top Border Patrol agent in the Rio Grande Valley region of South Texas summoned more than 20 local mayors, law enforcement personnel and other regional leaders to McAllen’s Border Patrol station.
The Rio Grande Valley sector is the busiest in the country for apprehensions of unauthorized immigrants, and the agent, Manuel Padilla Jr., said he called the meeting to prepare for the possibility of the first caravan’s arrival there. Mr. Padilla told those at the meeting that the caravan could arrive at the South Texas border, but it could also show up in towns as far away as California. Of particular concern to local officials is the potential for long lines at international bridges, as those in the caravan seek to enter the United States and apply for asylum.
“As far as we’re concerned, we want to make sure we focus on the ports of entry, so that there’s enough help at the bridges so people can get through the port and apply for asylum,” said Sister Norma Pimentel, who attended the meeting as the leader of Catholic Charities of the Rio Grande Valley, which assists migrants after they have been processed at the border and released. She said there was a concern that such large groups could overwhelm facilities along the border.
The officials discussed how to provide health assistance to the migrants. And since the meeting, the officials have been exploring options to add temporary housing, including at churches, because existing temporary shelter space is inadequate.
Chief Victor Rodriguez of the McAllen Police Department, who was also at the meeting, said he was always on standby to assist other agencies. But he was unsure what mission needed to be carried out as the caravan continued to head for the United States and the troops prepared to deploy.
“You’ve heard the saying: ‘This is a moving target,’” Chief Rodriguez said. “This is not even a target yet, it’s just moving. It’s like Jell-O. There are so many moving parts to this, and until we know what mission we’re trying to carry out, it’s hard for us to even plan to give assistance.”
The chief said he did not believe military options would be called for if and when the migrant caravan arrived in Texas. “My opinion is, if you were that person on the caravan down there and all of a sudden you see pictures of the military on the border, you’re getting the message that you’re not wanted,” he said.