President Trump authorized the military to take control of federal land stretching across three states at the southern border to assist in implementing his crack down on immigration.

The president directed the secretaries of Defense, Interior, Agriculture and Homeland Security, in a Friday evening memorandum dubbed “Military Mission for Sealing the Southern Border of the United States and Repelling Invasions,” to provide the Pentagon with jurisdiction of federal lands including the Roosevelt Reservation, which spans across California, Arizona and New Mexico. 

“Our southern border is under attack from a variety of threats,” Trump said in a presidential memorandum released Friday evening. “The complexity of the current situation requires that our military take a more direct role in securing our southern border than in the recent past.” 

Native American reservations are excluded from the order, which argues the move will help “maintain the sovereignty, territorial integrity and security” of the country. The land in question would be designated as “National Defense Areas” by Defense Secretary Pete Hegseth. 

Trump said the transfer of authority would allow military activities, including “border-barrier construction and emplacement of detection and monitoring equipment.” 

The progress of the initial phase would be evaluated in 45 days, the order says. 

Immediately after returning to the White House, Trump signed several orders focused on curbing illegal immigration, including the declaration of a national emergency at the southern border. Soon after, the administration deployed troops at the U.S.-Mexico border where they have worked with state troopers and members of the National Guard. 

The commander-in-chief has heavily campaigned on minimizing illegal immigration. The number of illegal crossings at the southern border have fallen off significantly in recent months.

There were around 7,200 crossings at the southern border in March, according to Border Patrol data. In the previous four years, the monthly average was 155,000. 

Earlier this week, the Department of Homeland Security issued its first waiver to speed up the construction of the border wall, which Trump touted during his first run for office nearly a decade ago.