TOPSHOT - Aerial view of Central American migrants moving towards the United States in hopes of a better life, sitting over the US-Mexico border fence in Playas de Tijuana, Mexico, on November 14, 2018. - US Defense 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)