Orange no-entry signs posted by the U.S. military in English and Spanish dot the New Mexico desert, where a border wall cuts past onion fields and parched ranches with tufts of tall grass growing amidst wiry brush and yucca trees.

The fourth national defense area created along the US-Mexico border will be an extension of Marine Corps Air Station Yuma in the Sonora Desert.

One third of the southern border is now covered by military zones, which allow troops to detain migrants attempting to enter the country unlawfully. The Associated Press detailed that the zones are being patrolled by at least 7,600 armed forces members as the Trump administration ramps up the presence of troops at the border.