The U.S. Capitol Building is visible as National Guard troops walk along the National Mall. “Chicago about to find out why it’s called the Department of WAR.”Trump has long promised to deploy the National Guard to America’s major urban hubs. In August, he deployed the National Guard to Washington, D.C., seizing on instances of violent crime to claim a public emergency. “He has the constitutional authority to employ the National Guard, and that’s part of the powers of commander in chief in Article II. AdvertisementSending in the National Guard without a governor’s consent was a highly unusual step.