(CNN) — Defense Secretary James Mattis has authorized the deployment of more troops to the US-Mexico border, the Pentagon announced Friday. The deployment will start with an undetermined number of forces heading to the border by the end of the month, and could eventually grow in size to 800 troops or more, a defense official said. It's a move aimed at sending a message as a migrant caravan makes its way through Mexico, bound for the US border, drawing the ire of President Trump. But it's important to note that even though troops are involved, the military isn't bracing for...