TOPSHOT - A Central American migrant woman and children moving towards the United States in hopes of a better life, walk next to buses 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)