U.S. officials say active duty military troops are arriving in El Paso, Texas, and in San Diego on Thursday evening.

A U.S. Border Patrol agent killed during a traffic stop near the Canadian border worked security duty at the Pentagon during the time of the Sept. 11 attacks.

The I Marine Expeditionary Force is made up of about 53,000 active-duty troops, who are primarily stationed at Camp Pendleton, as well as at Marine Corps Air Stations Miramar and Yuma, and the Marine Corps Air/Ground Combat Center at 29 Palms, California.

The move enacts President Trump's executive orders issued shortly after he took office to intensify immigration enforcement.

Trump signed executive orders aimed at building military presence along the border and designating cartels as foreign terrorist groups, here's what's next.

The deployment signals the military’s increased role in a much more aggressive immigration policy under the second Trump administration.

The Pentagon is sending up to 1,500 troops to help secure the southern border as President Trump pushes to stem the tide of migrants entering the country. Acting Defense Secretary Robert Salesses

Acting Defence Secretary Robert Salesses said the Pentagon will provide military aircraft to support Department of Homeland Security deportation flights for more than 5,000 detained migrants and the troops will assist in the construction of barriers.

A U.S. Border Patrol agent who was killed during a traffic stop in Vermont near the Canadian border was a military veteran.

Defense officials did not rule out arming troops on the border, but left that up to the discretion of NORTHCOM.

The Pentagon will deploy up to 1,500 active-duty troops to the U.S. border with Mexico, following executive orders from President Donald Trump to use the military to seal the border.