President Trump on Tuesday told a gathering of military leaders they should use American cities as "training grounds" and described a federal crackdown on crime in major cities as "a war from within." Trump addressed dozens of top generals and admirals in Quantico, Va., where he said defending the homeland was the military's "most important priority." He signaled that the leaders in the room could be tasked with aiding in federal interventions in Democratic-led cities like Chicago and New York City. "They're very unsafe places, and we're going to straighten them out one by one," Trump said. "And this is going to be a major part for some of the people in this room. That's a war too. It's a war from within."