Department of Homeland Security Secretary Kirstjen Nielsen inaugurates a newly completed renovated section of the border wall at the U.S.-Mexico border in Calexico, Calif. As a migrant caravan heads toward the U.S., Nielsen says her agency has asked for the military’s help.

Department of Homeland Security Secretary Kirstjen Nielsen inaugurates a newly completed renovated section of the border wall at the U.S.-Mexico border in Calexico, Calif. As a migrant caravan heads toward the U.S., Nielsen says her agency has asked for the military’s help.