WASHINGTON — National Guard troops began arriving at the D.C. Armory on Tuesday morning to report for duty to carry out President Donald Trump's directive to address crime in the nation's capital.

National Guard troops are arriving in Washington after President Donald Trump announced on Monday that 800 National Guard troops would be deployed as he declared a public safety emergency -- despite the city’s mayor noting violent crime is at a 30-year low.

If President Trump deploys troops to other American cities, experts say it would be a clear departure from founding principles and invite a legal challenge.