The National Guard is a reserve force of the U.S. military that is typically deployed by states in response to natural disasters, although it has been used in the past by presidents to help quell domestic unrest - including President George H.W. Bush during the Los Angeles riots in 1992.

On Tuesday night, more than 1,450 federal law enforcement officers and National Guard members patrolled Washington, according to a White House official. Forces made 43 arrests on Tuesday night -- nearly twice the amount they made Monday night.