WASHINGTON >> The Pentagon is intensifying efforts to identify and combat white supremacy and other far-right extremism in its ranks as federal investigators seek to determine how many military personnel and veterans joined the violent assault on the Capitol.

In the days since a pro-Trump mob breached the Capitol on Jan. 6, senior leaders of the 2.1 million active-duty and reserve troops have been grappling with fears that former or current service members will be found among the horde.

The FBI investigation into the Capitol siege, still in its very early stages, has identified at least six suspects with military links out of the more than 100 people who have been taken into federal custody or the larger number still under investigation. They include a retired Air Force lieutenant colonel from Texas, an Army officer from North Carolina and an Army reservist from New Jersey. Another person with military service was shot and killed in the assault.

The military’s examination of its ranks marks a new urgency for the Pentagon, which has a history of downplaying the rise of white nationalism and right-wing activism, even as Germany and other countries are finding a deep strain embedded in their armed forces.

“These people are not representative of our country’s military,” Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff, said. He said most active-duty troops and veterans “continue to serve honorably and uphold their oath to protect and defend the U.S. Constitution.”

For more than a week now, Milley has listened to analysts, read reports and viewed videos of the riots. “There was some indication that an unknown number of veterans associated with the insurrection,” he said.

Milley said he saw rioters carrying military flags. At the rally and later at the Capitol breach, rioters were seen with Marine Corps flags, Army patches and Special Forces insignia.

Federal officials are vetting thousands of National Guard troops arriving to help secure the inauguration. Of the 21,500 Guard personnel who had arrived in Washington by Monday, any who will be near President-elect Joe Biden and Vice President-elect Kamala Harris will receive additional background checks, a standard procedure to counter insider threats that was also taken before President Donald Trump’s inauguration in 2017.

Defense Department officials say they are looking into stepping up the monitoring of social media postings from service members, in much the way companies do with their employees.

Ashli Babbitt, who was shot and killed trying to climb through a door in the Capitol, was an Air Force veteran with a robust social media presence.

Among the suspects with military ties are Timothy Hale-Cusanelli, another protester at the Capitol, who federal agents say is a neo-Nazi and white supremacist; he also is an Army reservist who works — with secret clearance — at a naval weapons station.

Capt. Emily Rainey, an Army officer who told The Associated Press that she had transported 100 people to Washington for the Trump rally, is being investigated by the Army for any connection to the riots, according to a military official. Rainey had resigned from her post last year but was not set to leave until this spring.

Milley said he saw reports that “people were showing their CAC cards,” a reference to the identification cards used to enter military installations and the Pentagon.

Last Tuesday, Milley and the rest of the Joint Chiefs of Staff sent an extraordinary letter to all military personnel, reminding them that Biden would soon be their commander in chief and that they were duty bound to defend the Constitution.

The Defense Department inspector general announced an investigation last week into the effectiveness of Pentagon policies and procedures that prohibited service members from advocacy of or participation in supremacist or extremist groups.

The reckoning at the Pentagon comes as retired Gen. Lloyd J. Austin III is poised to become the nation’s first Black defense secretary, an ascension that, depending on how Austin decides to proceed, could either sharpen or blur the U.S. military’s decadeslong battles with racial inequality and white supremacy.

In his 41-year career in the Army before retiring as a four-star general in 2016, Austin witnessed firsthand both the possibilities and the limitations of how the military deals with race. As an Army officer, he has told of how he had to confront troops with Nazi insignia at Fort Bragg, North Carolina, and of countless meetings when he was the only person of color in the room. Now, if he is confirmed as defense secretary, he will have to decide if he will confront the far-right politics that have heightened during four years under Trump.

“This needs to be rooted out of our military,” Sen. Tammy Duckworth, D-Ill., and an Iraq War veteran, said in an interview last week. Austin, she said, “will be in a unique position to head up that effort.”

Austin’s confirmation hearings begin Tuesday, and lawmakers will most likely press him on how he plans to tackle extremism in the ranks.

Pentagon officials have known for some time that they have a problem. The Defense Department routinely brags that the U.S. military is a microcosm of American society — but officials now acknowledge that if a segment of American society holds white supremacist views, that means there will be a similar segment of the military that does, too.

Last year, the FBI notified the Defense Department that it had opened criminal investigations involving 143 current or former service members. Of those, 68 were related to domestic extremism cases, according to a senior Pentagon official. The “vast majority” involved retired military personnel, many with unfavorable discharge records, the official said.

The majority of the domestic extremism cases involved anti-government or anti-authority motivations, including attacks on government facilities and authorities, the official said. One-quarter of the cases were associated with white nationalism. A small number were associated with anti-fascist or anti-abortion motivations.

The acting secretary of defense, Christopher C. Miller, directed Pentagon officials last month to toughen policies and regulations banning extremist activities among troops, and update the Uniform Code of Military Justice to specifically address extremist threats.

“We in the Department of Defense are doing everything we can to eliminate extremism,” Garry Reid, the Pentagon’s director for defense intelligence, told reporters last week. Reid, however, was unable to outline specifics and declined to address any aspect of active duty members’ participation at the Capitol.

Rising concerns about right-wing activism in the armed forces are not concentrated only in the United States. In Germany, security services counted more than 1,400 cases of suspected far-right extremism among soldiers, police officers and intelligence agents in the three years ending in March, according to a government report released in the fall.

The U.S. military, unlike police departments and other law enforcement groups, has the ability to use extremist beliefs to disqualify those seeking to join. But, critics note, it has repeatedly failed to broadly apply those mandates.

“The military has unique abilities to set boundaries on conduct that other parts of government don’t have,” said Katrina Mulligan, managing director of national security and international policy at the Center for American Progress, a liberal think tank. “But they have been unevenly applied.”

Military officials and independent specialists say Austin will face a daunting challenge. Pentagon officials concede that despite the checks in place, white supremacist and other far-right groups actively recruit service members or have their own members try to join the military to learn skills and expertise, which also lends legitimacy to their cause.

All military personnel, including those in the National Guard, undergo extensive background investigations and physical examinations including assessments of tattoos. Troops are continuously monitored for indications that they are involved in extremist activity and receive training to identify others around them who could be “insider threats.”

But critics say the military’s leadership has often failed to hold violators accountable consistently.

“Current regulations have penalties that are largely left up to commanders, often at the unit level,” Heidi Beirich, a co-founder of the Global Project Against Hate and Extremism, told a House hearing in February. “There appears to be no process to track people expelled for ties to white supremacists’ groups.”

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