During a news conference at the White House on Monday, the US president said the city’s police would come under federal control as he said the murder rate in DC was “higher than” in some of the “worst places on earth”.
He said he was deploying the troops to “re-establish law, order, and public safety”.
Mr Trump said he was announcing a “historic action to rescue our nation’s capital from crime, bloodshed, bedlam and squalor and worse.
“This is liberation day in DC and we are going to take our capital back.”
The president went on: “So today we are declaring public safety emergency in the district of Columbia.”
He added it is not just about safety but also “beautification” of the city.
“Washington DC should be one of the safest, cleanest and most beautiful cities anywhere in the world and we’re going to make it that.”
Last week, the Republican president directed federal law enforcement agencies to increase their presence in Washington for seven days, with the option “to extend as needed.”
On Friday night, federal agencies including the Secret Service, the FBI and the US Marshals Service assigned more than 120 officers and agents to assist in Washington.
National guard troops usually belong to individual states and personnel in many cases are trained to help with emergencies that those states have to deal with, such as natural disasters.
Since they are the reserve force of the US military, National Guard troops are usually part time, meaning that they have other jobs as well.
On Sunday, Mr Trump in a social media post had emphasised the removal of Washington’s homeless population, though it was unclear where the thousands of people would go.
“The Homeless have to move out, IMMEDIATELY,” Mr Trump wrote.
“We will give you places to stay, but FAR from the Capital. The Criminals, you don’t have to move out. We’re going to put you in jail where you belong.”
