WASHINGTON – U.S. Marshals have been told they should prepare to help protect national monuments across the country, according to an email directive viewed by The Washington Post, as President Donald Trump has vowed stern punishment for those who vandalize or destroy such structures as part of police violence protests.

In an email, Marshals Assistant Director Andrew Smith wrote that the service “has been asked to immediately prepare to provide federal law enforcement support to protect national monuments (throughout the country).”

“This is a challenging assignment due to the breadth of possible targets for criminal activity,” Smith wrote. He said the Marshals Incident Management Team would start a Joint Operations Center in Springfield, Va., to coordinate, and every deputy in the Special Operations Group would be made available to help as soon as Thursday. He also asked other districts and divisions to identify people they might be able to lend to the effort until July 8.

On Monday, protesters attempted to topple a statue of President Andrew Jackson in a park next to the White House, though police in riot gear intervened and stopped them. That night, Trump tweeted his dismay, and the next morning he wrote that he had “authorized the Federal Government to arrest anyone who vandalizes or destroys any monument, statue or other such Federal property in the U.S. with up to 10 years in prison, per the Veteran’s Memorial Preservation Act, or such other laws that may be pertinent…..”

Earlier Wednesday, defense officials said that the Army activated about 400 unarmed members of the District of Columbia National Guard to “prevent any defacing or destruction” of monuments.

Jackson, a former general in the U.S. Army, was known for his harsh treatment of Native Americans as president. He signed the Indian Removal Act, which led to the relocations of thousands of Native Americans and the deaths of thousands more.