The newly annexed 250-mile stretch at the border spans two counties and runs alongside cities including Brownsville and McAllen.

This marks the third National Defense Area to be established on the southern border of the U.S., and joins over 200 miles monitored by a federal taskforce created in March.

The plans for strips of land in Texas and Arizona are the latest step to militarize the boundary to stem an already dwindling number of migrant crossings.