Around two dozen soldiers stood guard outside Washington, Union Station in Washington, D.C., on Aug. 14. They had little to do.

The idea is that residents and tourists would awake Thursday morning to the sight of military presence, according to a person familiar with the effort.MORE: Trump to seek 'long-term' extension of federal control of DC policeEarlier this week,

The 800 soldiers, in round-the-clock shifts of 100 to 200, will support Washington police and federal law enforcement officers.