The Pentagon is experiencing continuing aftershocks from the Jan. 6 insurrection — the frightening recognition that many of the people who assaulted the Capitol that day saw themselves as part of the military family.

Military leaders have long known they had a problem with white extremism in the ranks. Many senior commanders describe incidents early in their careers when they had to discipline troops who had racist tattoos or links to extremist groups. But they didn’t fully realize how dangerous the spread of this extremist ideology could become for the country — until the wake-up call on Jan. 6.

“A commander who tells you that there’s no problem really doesn’t know what’s going on in his own unit,” argued Gen. Kenneth Frank McKenzie Jr., who heads U.S. Central Command, in an interview during a trip to the Middle East. If military leaders don’t address these problems within the ranks, “then you need to get new leaders,” McKenzie said.

Defense Secretary Lloyd Austin ordered a military-wide stand-down on Feb. 5 so that commanders could talk with their forces about extremism. Officers were advised to review the meaning of the oath that military personnel sign, and to review “impermissible behaviors” and how to report them.

This process of internal discussion will end in early April, but it’s already clear that the extremist views of the Capitol rioters are shared by some active-duty forces. “It is real. It is not an imaginary problem. It exists,” said John Kirby, the Pentagon spokesman, in an interview Tuesday about the danger of extremism in the military. He told me that one difficulty in assessing the threat is that extremists are secretive about their views. “These people often live in darkness, thrive in darkness and conceal their belief systems.”

Kirby said that Austin is focusing on three corrective measures: tighter screening of recruits before they join the armed forces; closer monitoring of whether military personnel are being radicalized while they’re on active duty; and better communication about values with men and women who are about to leave the military and become veterans.

Anger and chagrin about Jan. 6 are widely shared in the Pentagon. “I was outraged that any service member took part in the attack on the Capitol because it was an attack on the Constitution and we are sworn to defend the Constitution,” said Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff, in an email sent through his spokesman Tuesday.

Warning signs of growing extremism in the military are obvious, in retrospect. A 59-page Pentagon report last June to the congressional armed services committees warned that the Defense Department “is facing a threat from domestic extremists . . . particularly those who espouse white supremacy or white nationalist ideologies.” Drawing on FBI evidence, the report listed examples of extremist behavior. But the information didn’t receive any public attention until this month.

The Oath Keepers, a militant group formed by a former Army paratrooper, is probably the best example of an insurrectionist group that tries to feed off the military culture. Back in 2016, it claimed to have 30,000 members “who were said to be mostly current and former military, law enforcement and emergency first responders,” according to the Southern Law Poverty Center. Federal prosecutors recently charged nine alleged members or associates of the group with conspiring to obstruct Congress in the Jan. 6 riot.

These self-styled patriots waved the stars and stripes even as they assaulted the House and Senate chambers. A court document released Monday quotes Thomas Caldwell, a former Navy intelligence officer charged as a member of the Capitol conspiracy, recalling that on Jan. 6, “it was exhilarating to stand there with thousands . . . waving my American flag . . . singing ‘America the Beautiful’ and ‘The Star-Spangled Banner.’ ” Caldwell was allegedly in regular contact with Oath Keepers leaders but denies he was a dues-paying member.

McKenzie argues that one reason the military has spawned extremists is that the volunteer force that fought our wars in recent decades began to see itself as a warrior “elite.” The four-star Marine general explains: “You can come back [from deployments abroad] and feel that you’re inherently superior to your fellow citizens. Perhaps you’ve borne a very heavy share of the responsibilities. . . . But actually, we’re all citizens in the end.”

When the symbols of patriotism are embraced by one side in a divided country, they become political emblems. Who could have imagined that singing the national anthem or saluting the flag, or, for that matter, wearing a mask, could become a polarizing ideological statement?

The military carried a heavy load for the country the past two decades, and perhaps that made some veterans feel they had a special status as protectors of the republic — even to the treacherous point of insurrection.

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