The new military buffer zones stretch across 230 miles from Fort Hancock, Texas, to western New Mexico, with an additional 250-mile zone recently implemented in Texas’ Rio Grande Valley. Another zone is planned near Yuma, Arizona. Collectively, these areas now account for nearly one-third of the entire U.S.-Mexico border. Oversight is divided between Army commands at Fort Bliss in Texas and Fort Huachuca in Arizona. According to the Pentagon, the zones are intended to close enforcement gaps in isolated desert regions and to combat human smuggling networks and drug trafficking activity that continue to exploit weaknesses in the current system.

This expanded military presence is being patrolled by at least 7,600 active-duty troops, marking the largest peacetime deployment of military forces for immigration enforcement in U.S. history. These deployments allow troops to detain migrants and oversee stretches of the border previously managed exclusively by Customs and Border Protection. Officials argue that the move strengthens national security and provides “teeth” to long-standing surveillance operations. However, legal experts and civil liberties groups have raised alarms over what they view as an erosion of the Posse Comitatus Act, the 1878 law prohibiting the military from carrying out civilian law enforcement functions without congressional approval.