A look at troops being sent to U.S.-Mexico border and their mission

WASHINGTON — President Donald Trump ordered troops to the border in response to a caravan of migrants slowly making its way through Mexico toward the United States and still about 900 miles away, with many dropping out. Here’s what we know so far about the military’s mission:

What troops are involved?

More than 7,000 active duty troops have been told to deploy to Texas, Arizona and California. They are a mix of forces, including military police, an assault helicopter battalion, various communications, medical and headquarters units, combat engineers, planners and public affairs units.

As of Friday, one week after the Pentagon acknowledged that Defense Secretary Jim Mattis had approved a Department of Homeland Security request for military support at the border, the troop deployment was still unfolding, with about 3,500 at staging bases in the Southwest.

Their role at the border

The Pentagon is adamant that active duty troops will not do law enforcement, which they are forbidden from doing under the Posse Comitatus Act in the Constitution. Their job is to support the Border Patrol.

This means the military will transport border patrol agents to and along the border, help them erect additional vehicle barriers and fencing along the border, assist them with communications and provide security for border agent camps.

Will they be armed?

Yes, many of them will be, mainly for self-protection.

Military police at the border will be armed, although they will have nonlethal options for dealing with unexpected conflict. Pentagon officials say they are planning for a worst-case scenario of violence that could force soldiers to rely on their training to make split-second decisions to defend themselves or civilians.