The deployment is part of Trump's executive action to declare a "national emergency" at the U.S. southern border.

The U.S. military has begun sending 1,500 active-duty troops to the country's southern border with Mexico as part of President Donald Trump's long-promised crackdown on immigration.

The White House confirmed the troop movement on Wednesday, but full details of the order have not yet been released.

Officials told US media that the troops involved included 500 Marines. They should not have law enforcement duties as part of their duties at the border.

The troop deployment was widely expected as immigration has been a hallmark of Trump's reelection campaign.

Shortly after being sworn in on Monday, the Republican leader signed an executive order declaring a "national emergency" at the border, repeating some of the fiery rhetoric he made on the campaign trail.

"The sovereignty of the United States is under attack," the executive order said. "This invasion has caused widespread chaos and suffering in our country over the past four years."

The order includes provisions for deploying armed forces “in support of the Secretary of Homeland Security’s activities to obtain full operational control of the southern border.”

It also calls for more physical barriers, as well as the use of drone surveillance.

Trump's communications team was quick to praise Wednesday's troop deployment as fulfilling his election-season promises.

“This is what President Trump campaigned on,” White House press secretary Caroline Leavitt said.

“The American people have been waiting for a moment like this — for our Department of Defense to really get serious about homeland security.”

An estimated 2,500 U.S. National Guard members and reservists are already at the border.

In addition, U.S. Customs and Border Protection has more than 45,000 employees. As of fiscal year 2023, 19,104 of those employees serve as Border Patrol agents, protecting the area between official ports of entry.

However, immigration advocates worry that an increased military presence at the border could impede legitimate asylum claims or lead to the use of military tactics against civilians.

But Trump argued that a military response was needed given the number of people entering the United States irregularly.

He also often confers immigration with increased crime, but the statistics don't bear this out. Studies have repeatedly shown that undocumented people in the United States commit crimes, including violent crimes, at much lower rates than U.S.-born citizens.

Still, Trump used examples such as Laken Riley, a 22-year-old nursing student, to advance his proposal.

Riley was killed while jogging at the University of Georgia in February 2024, and an undocumented Venezuelan man was ultimately convicted of her murder.

On Wednesday, the House of Representatives passed the Laken Riley Act, named in her honor.

It requires Immigration and Customs Enforcement (ICE) to detain any undocumented person arrested or charged with a crime such as theft or robbery. The bill has passed the Senate and will now go to Trump's desk, where he is expected to sign it. It would be his administration's first major piece of legislation.

But human rights advocates have warned that the bill could violate due process for defendants because people subject to the law would only have to be charged with a crime, rather than convicted.