All armed National Guardsman on duty in DC vetted by FBI amid inauguration threats

Every one of the armed National Guardsmen deployed around the U.S. Capitol and the streets of Washington, D.C., to help with security for Wednesday's presidential inauguration has already been vetted by the FBI as they look for any potential insider threats, according to a defense official.

There are now 21,500 National Guardsmen in the city who have arrived from all 50 states and three territories, building up to a force of 25,000 by Wednesday in what the Guard calls Operation Capital Response. The dozens of vehicle checkpoints, miles of protective fencing and concrete barriers, and the sight of armed guardsmen has given Washington the look of a fortress.

The significant Guard presence was requested by the Secret Service, which wants to prevent a recurrence of the violence carried out by a mob of President Donald Trump's supporters in their assault on the U.S. Capitol two weeks ago.

"While we have no intelligence indicating an insider threat, we are leaving no stone unturned in securing the capital," acting Defense Secretary Chris Miller said in a statement issued Monday.

"This type of vetting often takes place by law enforcement for significant security events," said Miller. "However, in this case the scope of military participation is unique."

The security concerns surrounding Wednesday's inauguration have led to the buildup of a Guard force 2.5 times larger than had been expected prior to the riot at the Capitol.

It also means that guardsmen helping with security at the Capitol building area are armed, while other guardsmen assisting in other parts of the city on different missions may have their weapons with them though they are not loaded.

The FBI's screening of National Guardsmen begins as they arrive at the D.C. Armory to begin the process of obtaining Secret Service-issued credentials needed to access secure areas surrounding the inauguration, said Maj. Matthew Murphy, a National Guard spokesman.

It is there that every arriving guardsman gets their photo taken and hands over their military ID card, which is then placed into a database used by the FBI for background checks.

"If there's any indication that any of our soldiers or airmen are expressing things that are extremist views, it's either handed over to law enforcement or dealt with the chain of command immediately," Gen. Daniel R. Hokanson, the chief of the National Guard Bureau, said in a statement.

The civilian in charge of the Department of the Army said the vetting of guardsmen is continuous.

"We're continually going through the process, and taking second, third looks at every one of the individuals assigned to this operation," Secretary of the Army Ryan McCarthy told the Associated Press on Sunday.

The D.C. Guard is also providing additional training to the guardsmen -- that if they see or hear something that is inappropriate from someone in the ranks, they should report it through their chain of command.

"There is no place for extremism in the military and we will investigate each report individually and take appropriate action," according to a National Guard statement.

As part of their normal training, all military service members are trained annually on the Threat Awareness and Reporting Program (TARP), which similarly requires personnel to report any information regarding any known or suspected extremist behavior that could pose a threat to the United States or the military.

Concerns surrounding potential violence pegged to the inauguration are not limited to Washington.

At least 21 states have also activated their National Guardsmen to provide security at state capitol buildings, given the possibility that they might be targeted by extremists who support Trump.

This report was featured in the Tuesday, Jan. 19, 2020, episode of "Start Here," ABC News' daily news podcast.

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