Acting Defense Secretary Chris Miller takes part in a virtual call from the Pentagon, Washington, D.C., on Jan. 4, 2021. (Lisa Ferdinando/Department of Defense)

Acting Defense Secretary Christopher Miller quietly ordered a review last month of the Pentagon’s policies on extremist activities among service members, a senior defense official said Thursday, acknowledging the growing concern of troops harboring extreme views.

Officials in the five military services involved in the recruiting and accessions policy and those in the Pentagon’s personnel and readiness office are due to draft a report within two months outlining new initiatives meant to stamp out extremists or hate group activity in the ranks, the senior defense official said. The official spoke on condition of anonymity to speak about the issue that has gained attention as some current and former service members face scrutiny over their alleged involvement last week in the deadly storming of the U.S. Capitol.

The review was ordered before Jan. 6, the day that a mob of President Donald Trump’s supporters marched on the Capitol building after listening to the president speak near the White House. The senior official and other Pentagon officials declined to comment on the participation of current or former troops in the attack, citing the Justice Department’s ongoing investigations. No active-duty troops are known to have been charged with crimes related to the incident, however some military veterans have been charged.

Two senior defense officials said Thursday that Pentagon officials were most concerned with extremist activity among troops and veterans aligned with anti-government militia movements and those who hold white supremacist views.

“We know that some groups actively attempt to recruit our personnel into their cause, or actually encourage their members to join the military, for purpose of acquiring skills and experience,” one official said. “We recognize that [military] skills are prized by some of these groups.”

The groups also believe having military veterans within their ranks lends some sense of “legitimacy, in their mind, to their cause.”

“The fact that they can say they have former military personnel that align with their extremist and violent extremist views, clearly is of great concern to us,” this official said.

The Pentagon has a zero-tolerance policy for any extremism among its forces. But some Defense Department officials and members of Congress have been critical of the department’s efforts to keep extremists from its ranks. The 2021 National Defense Authorization Act, which sets annual Pentagon policy and spending priorities, contained measures meant to help the department address the issue, including the creation of a new position within the DOD inspector general’s office — the deputy inspector general for diversity and inclusion and supremacist, extremism and criminal gang activity. Congress also charged the inspector general with establishing a “mechanism to track and report” extremist or gang activity in the military.

All military troops are screened for indications that they hold extremist viewpoints or are involved in extremist activity, Garry Reid, the director of Defense Intelligence, said in a statement issued Thursday. Those screenings include extensive background investigations and physical examinations including assessments of tattoos. Reid said troops, including members of the National Guard, are continuously monitored for indications that they are involved in such activity and received training to identify others around them who could be “insider threats.”

“We in the Department of Defense are doing everything we can to eliminate extremism in the Department of Defense,” he said Thursday. “DOD policy expressly prohibits military personnel from actively advocating supremacist, extremist or criminal gang doctrine, ideology or causes. … Simply put, we will not tolerate extremism of any sort in the DOD.”

The senior defense officials said they could provide no data showing a rise in extremist activity among service members. They pointed to anecdotal evidence of an increase of such activity in the military and society at large, including the arrest last year of an active-duty Air Force sergeant allegedly involved in the anti-government “boogaloo” movement, who was charged in the killing a federal agent in California.

Among the military veterans arrested in connection with the riot at the Capitol were retired Air Force Lt. Col. Larry Rendall Brock Jr., a former A-10 pilot photographed carrying zip-tie handcuffs in the Senate chamber, and Jacob Anthony Chansley, who goes by Jake Angeli and is known as the "QAnon Shaman," among followers of the far-right conspiracy theory. Chansley, who was photographed inside the Capitol shirtless and wearing a horned headdress, served in the Navy from September 2005 to October 2007, according to his service records.

An Air Force veteran, Ashli Babbitt, who supported Trump and the QAnon conspiracy on her social media pages, was shot to death inside the Capitol by law enforcement during the riot.

A former Navy SEAL, Adam Newbold, has been questioned by the FBI after posting a video on social media last week describing “breaching the Capitol.” And, the Army is investigating a Fort Bragg, N.C.-based captain, Emily Rainey, who admitted attending the rally before the violent attack on the Capitol. She told The Associated Press this week that she did not enter the building or break any laws or Army regulations.

Rainey is set to leave the Army in April after resigning her commission last year over a prior infraction. She is the only known active-duty service member under investigation in connection with the Jan. 6 events.

As thousands of National Guard troops pour into Washington, D.C. in the coming days amid threats of more violence in the national capital ahead of President-elect Joe Biden’s Jan. 20 inauguration, some have called for added scrutiny of those troops charged with helping local and federal law enforcement secure the city. Rep. Jason Crow, D-Colo., a former Army Ranger, said this week that he asked the Army to review the backgrounds of Guard troops entering the city “to ensure that deployed members are not sympathetic to domestic terrorists.”

Law enforcement officials are concerned about the potential for violence during a series of protests, primarily in support of Trump, planned for Washington between Saturday and Jan. 24, local and federal officials said Wednesday.

The senior defense officials did not indicate whether Guard troops would face new screening for extremist views before they were deployed for inauguration support. An Army official, who spoke on condition of anonymity, said some troops were expected to be screened.

As of Thursday, some 7,000 National Guard troops from 13 states and D.C. had arrived in Washington to support local and federal police efforts, especially around the Capitol, according to a National Guard statement. Some Guard troops at the Capitol have been armed with their service weapons, Guard officials said. Troops serving at other locations throughout the city are not armed, they said.

Army Gen. Daniel Hokanson, chief of the National Guard Bureau, said at least 10,000 troops were expected to be on duty in Washington by Saturday. The Pentagon has authorized up to 15,000 troops from 43 states to serve in D.C during the inauguration, the Guard said.

A Pentagon spokesman said that number could grow again. Local and federal police officials have asked for another 5,000 troops by Jan. 20, but the Pentagon had not formally approved the additional deployments as of Thursday, the spokesman said.