Pentagon Chief Jim Mattis is defending President Trump’s decision to send thousands of troops to the U.S.-Mexico border, saying it’s providing the soldiers with good training for war. Mattis toured a newly constructed military base near the border in McAllen, Texas, Wednesday alongside Homeland Security Secretary Kirstjen Nielsen. When asked by a soldier what the objectives of the deployment were, Mattis responded, “Long term, it is somewhat to be determined.” The visit came as some migrants arriving at the U.S.-Mexico border in California attempted to enter the U.S. Wednesday. At least nine people were arrested by Border Patrol.