U.S. Army soldiers will soon be patrolling a 170-mile buffer zone along the southern border with Mexico in a newly created "National Defense Area" in Arizona and New Mexico. It's part of the Trump administration's efforts to use the U.S. military to stop the flow of undocumented migrants into the United States.

A long sliver of federal land along the U.S.-Mexico border that President Donald Trump is turning over to the Department of Defense would be controlled by the Army as part of a base, which could allow troops to detain any trespassers,