SUNLAND PARK, N.M. - Pvt. Daniel Aguilar joined the Army a year ago and trained to operate a howitzer. But since February, he has been monitoring video screens inside trucks in remote areas of New Mexico, doing a job that had been done by Border Patrol agents.

"I was not expecting this at all," Aguilar, 20, said about what he envisioned when he enlisted in his hometown of Bear Lake, Michigan. "I like it so far. I think it's a great opportunity to get to know how the Border Patrol agents conduct their job, how they do their mission."

Aguilar is one of 1,200 soldiers and Marines operating 150 Border Patrol mobile security cameras in California, Arizona, New Mexico and Texas as part of the active duty military assistance being provided by the Defense Department at the request of the Department of Homeland Security.

The camera operators make up the bulk of the 2,000 active-duty service members currently assigned to border missions, military officials said during a briefing Thursday on a remote bluff that provides a commanding view of thousands of square miles of the border region just outside El Paso, Texas.

Border Patrol agents would normally operate the 150 truck-mounted mobile security cameras, but they have been moved to other missions to process and care for the increasing surge of migrant families across the U.S.-Mexico borders. Customs and Border Protection officials announced Wednesday that almost 133,000 migrants had been taken into custody by the Border Patrol in May, the highest monthly total since 2006.

Military camera operators have assisted in about 13,000 apprehensions since February, and marijuana seizures totaling about 3,000 pounds. Those apprehensions generally are of people looking to surrender to Border Patrol agents, officials acknowledged, and account for about 3% of all apprehensions on the border since February.

"I gauge the value added by the feedback we get from our Border Patrol partners. They have the experience here on the border. They understand the dynamics here on the border and the challenges better than anyone," said Brig. Gen. Walter Duzzny, deputy commanding general of U.S. Army North and the commander of the active-duty military deployment to the border.

If they weren't deployed to the border, Aguilar and his fellow soldiers from the 1st Battalion, 37th Field Artillery Regiment at Joint Base Lewis McChord in Washington state would be training with their howitzers for potential combat deployment. The soldiers are still receiving valuable training, Duzzny said, even though they're 1,500 miles from their cannons.

"All that is involved in saying a unit is ready for their primary mission is very diverse, very complex. And many of the tasks that we are executing out here fall right in line with what a unit needs to be ready," he said.

Mobile security cameras are photographed in Sunland Park, New Mexico. About 1,200 soldiers and Marines are operating 150 Border Patrol mobile security cameras in California, Arizona, New Mexico and Texas as part of the active duty military assistance being provided by the Defense Department at the request of the Department of Homeland Security.  Photo for The Washington Post by Robert Moore.
Mobile security cameras are photographed in Sunland Park, New Mexico. About 1,200 soldiers and Marines are operating 150 Border Patrol mobile security cameras in California, Arizona, New Mexico and Texas as part of the active duty military assistance being provided by the Defense Department at the request of the Department of Homeland Security. Photo for The Washington Post by Robert Moore.

The soldiers and Marines operating the mobile security cameras work in 10-hour shifts and stay in hotels in their off hours. Aguilar and other service members deployed since February will soon return to their home bases, replaced by other units who will serve until September.

When they spot something suspicious, the soldiers and Marines operating the remote security cameras call Border Patrol agents to check out the activity.

"We are the eyes and ears of (Customs and Border Protection), and we give them around- the-clock situational awareness," Aguilar said. "And if we see anything, we call them up."

Soldiers and Marines carry sidearms but are instructed to use deescalation techniques if the encounter migrants crossing the border and call for assistance from Border Patrol agents.

Such encounters are rare, said Col. Paul Garcia, deputy commander of Joint Task Force North, which coordinates military border assistance. Military members interact with migrants perhaps once or twice a week, calling Border Patrol for assistance and providing water while waiting, he said.

"So it's been pretty benign. I'd say 99% of the time, we've had no issues," Garcia said.

This article was written by Robert Moore, a freelance journalist based in El Paso.