TOPSHOT - US Department of Defence personnel install barriers requested by Custom and Border Protection at the San Ysidro port of entry, San Diego, US, under the Operation Secure Line anticipating the arrival of Central American migrants heading towards the border, as seen from the Mexican side of the border in Tijuana, Mexico, on November 13, 2018. - US Defence Secretary Jim Mattis said Tuesday he will visit the US-Mexico border, where thousands of active-duty soldiers have been deployed to help border police prepare for the arrival of a "caravan" of migrants. (Photo by GUILLERMO ARIAS / AFP)