U.S. Marine Corps Lance Cpl. Christian Koch, a combat engineer with 8th Engineer Support Battalion, 2nd Marine Logistics Group, assigned to Joint Task Force-Southern Border, uses a tie gun to secure triple-strand concertina wire during barrier reinforcement operations in Douglas, Ariz., Friday, April 17, 2026. U.S. Northern Command is working side-by-side with the Department of Homeland Security and the U.S. Customs and Border Protection within narrowly defined authorities to provide unique military capabilities to protect the territorial integrity of the U.S. southern border. (Dept. of War photo by U.S. Marine Corps Lance Cpl. Destiny Perez)