“We’re preparing for an enormous turnout,” said Matt McCool of the Secret Service's Washington Field office, who said more than 18 miles of “anti-scale fencing” would be erected and “multiple drones” would be in the air. The entire District of Columbia is normally a no-fly zone for drones.

Preparations continue for the parade commemorating the Army’s 250th anniversary and President Donald Trump's birthday. The parade on June 14 will feature some 6,600 soldiers, artillery and military flyovers.