A mere four months into the second Trump administration, the U.S. military has been hurled into an unprecedented and dangerous role as a police force along designated stretches of the U.S.-Mexico border. This has not received as much attention as other components of the administration’s immigration policies, but it will come at great cost to American principles and security.
This uncharted territory for the U.S. military began almost immediately after President Donald Trump declared a national emergency at the southern border on Jan. 20 and directed the Defense Department to “[obtain] operational control.”
Additional units began arriving at the border, and the number of service members deployed to the border will reach almost 10,000 once an additional 1,115 active duty troops arrive.
Meanwhile, high-end assets designed to track and defend against sophisticated adversaries were repositioned into the area, a temporary holding area for migrants was established at Naval Station Guantanamo Bay and military transport aircraft removed migrants from the United States.
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Each deployment and announcement has been accompanied by visual reminders that the U.S. military now has an increased — and unprecedented — responsibility for securing the southern border.
Border security is inextricably linked to national security and the territorial integrity of the United States, and previous administrations have also supplemented Department of Homeland Security missions with DOD support. But the U.S. military’s role in border security has historically been extremely limited, for important reasons.
Since Jan. 20, the border has swiftly militarized in a manner that is unsustainable yet politically advantageous. As such, the U.S. military will find it hard to unwind its participation.
Deployments to the border come at the expense of other operations and exercises that only the military can perform to defend the country, including deployments to the Indo-Pacific designed to deter Chinese aggression.
The Department of Homeland Security will assume the DOD well is never dry, and continue to ask DOD for support that eclipses previous asks and pushes boundaries in alarming ways.
This is the entire point of subsequent presidential orders that probe the seam between the roles that U.S. troops traditionally fill at the border, such as detection and monitoring, and those assigned to civilian law enforcement agencies (LEAs), with their apprehension and detention authorities.
An April 11 presidential memorandum paved the way for the U.S. Army to designate two stretches of land contiguous with U.S. Army installations, Fort Huachuca and Fort Bliss, as new “national defense areas” where the military can apprehend trespassers and hand them to LEAs.
Thus, through a series of memos and delegations of authority, U.S. service members have been thrust into apprehending and temporarily detaining migrants within the new zones.
This effectively sidesteps the Posse Comitatus Act (PCA), which prevents the military from directly engaging in civilian law enforcement, except under certain limited circumstances. PCA is a firewall against the U.S. military morphing into a force for internal security or suppression of Americans.
The administration’s legal end-run is being met with some initial skepticism in the courts, with a judge dismissing trespassing charges against immigrants in these zones. But notwithstanding this relief, service members are being asked to police in their own country, albeit not against Americans. This is simply not a role for which they are trained and equipped.
Nor do the facts on the ground support this mission creep.
Border crossings, which were dropping at the end of the Biden administration, are reportedly down to historic lows, according to the Pentagon. A smaller military footprint could now support DHS at the border. Instead, we may see these troop deployments, expanded authorities and blurred military-police roles become the norm at the border — or stretched from the border into the interior of the country.
At that point, the American people may find themselves wondering when and how they should have spoken out.
Caroline Zier served as the deputy chief of staff to former Defense Secretary Lloyd Austin during the Biden administration.
