Senior military leaders, including the Joint Chiefs of Staff, condemned last week’s deadly riot by supporters of President Donald Trump as a “direct assault on the U.S. Congress” in statements issued this week and warned service members that participating in acts against the Constitution is against the law.

The Department of Defense “has authorized as many 15,000 troops” to deploy to Washington ahead of President-elect Joe Biden’s Jan. 20 inauguration, according to Army Times on Tuesday, and is taking steps to screen and train service members on the massive detail. The extra precaution comes after current former service members were identified as participants in the Jan. 6 insurrection at the Capitol.

By Wednesday, the projected force of Nation Guard deployment to D.C. had swelled to over 20,000, Politico reported, “after federal officials authorized a 5,000 member increase.”

“We are working with the Secret Service to determine which service members supporting the national special security event for the inauguration require additional background screening,” an Army spokesperson said in an email to Army Times. “The D.C. National Guard is also providing additional training to service members as they arrive in D.C. that if they see or hear something that is not appropriate, they should report it to their chain of command.”

“Folks, I took an oath to defend the Constitution of the United States. So did all of the men & women in this picture,” said Army Lt. Gen. Ted Martin in a tweet Tuesday, which includes a photo of a formation of soldiers saluting.

Martin is the deputy commanding general of the Army Training and Doctrine Command, the the Army command responsible for recruiting and training new Army recruits and service members during their their time in the Army.

“There is no place in our ranks for extremism. Not now. Not ever,” he added.

In a message to the nation’s military forces Tuesday, the Joint Chiefs of Staff said the “violent riot in Washington ... was a direct assault on the U.S. Congress, the Capitol building, and our Constitutional process,” according to Task & Purpose, a digital news publication that covers the military. In the individually signed memo, the leaders also said that Biden will be inaugurated as their new commander in chief.

“As service members, we must embody the values and ideals of the nation. We support and defend the Constitution,” Chairman Army Gen. Mark Milley wrote on behalf of the Joint Chiefs of Staff, Task & Purpose reported. “Any act to disrupt the constitutional process is not only against our traditions, values, and oath: it is against the law.”

On Monday, Sen. Tammy Duckworth, D-Ill., an Illinois Army National Guard Blackhawk pilot who lost her legs in combat in Iraq, called on the Pentagon to work with federal investigators to determine if active-duty or retired members of the military participated in what she referred to as a “coup attempt,” Politico reported.

In a letter to Chris Miller, the acting Secretary of Defense, the senator said if criminal investigators found that those members “engaged in criminal conduct related to Jan. 6, 2021, attack on the United States Capitol, I urge you to take appropriate action to hold individuals accountable under the Uniform Code of Military Justice.”

“Upholding good order and discipline demands that the U.S. Armed Forces root out extremists that infiltrate the military and threaten our national security,” Duckworth added.

On Sunday, Congressman Jason Crow, D-Colo., spoke with Army Secretary Ryan McCarthy about the Jan. 6 riot and what was being done to secure the upcoming inauguration.

Crow — a former Army Ranger with deployments to Iraq and Afghanistan — told McCarthy he was gravely concerned “about reports that active duty and reserve military members were involved in the insurrection,” according to notes of their meeting that the congressman posted on Twitter. Crow said he requested a review of the “troops deployed for the inauguration to ensure that deployed members are not sympathetic to domestic terrorists,” and that the Army Secretary “agreed to take additional measures.”

The messages from the senior military leaders and the Defense Department’s caution ahead of the inauguration comes after an active duty Army soldier, a retired U.S. Air Force officer and countless veterans were identified as participants in the deadly Washington riot. Ultimately five people were killed as Trump supporters broke through police lines and raided the Capitol building and at least two of those who died — a Trump supporter and a Capitol police officer — were veterans.

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The Associated Press reported Monday that the Army was investigating an active duty officer who led a group of 100 North Carolinians to the pro-Trump Washington rally last week and whether her actions broke Department of Defense policy for soldiers.

“I was a private citizen and doing everything right and within my rights,” Capt. Emily Rainey told the AP, who also said that no members of her group — the Moore County Citizens for Freedom — broke the law.

“Members of the U.S. military are permitted to take part in political organizations and events out of uniform. However, there are caveats. The Department of Defense directive prohibits active-duty service members from sponsoring partisan organizations. It is unclear if Rainey’s participation with her group on Wednesday went against DOD policy,” the AP reported.

The military is also investigation whether other active duty service members participated in violence inside the Capitol building.

Retired Air Force Reserve Lt. Col. Larry Rendall Brock Jr. was arrested in Texas and charged in D.C. federal court Sunday on charges of “knowingly entering or remaining in any restricted building or grounds without lawful authority” and for the “violent entry and disorderly conduct on Capitol grounds” in connection to the riot, according to a Justice Department press release.

“It is alleged that Brock was identified as one of the individuals who unlawfully entered the U.S. Capitol wearing a green helmet, green tactical vest with patches, black and camo jacket, and beige pants holding a white flex cuff,” the department said.

According to an interview with the New Yorker before the arrest, Brock said he was the man dressed in the above attire that was seen in photos and video of the Capitol riot. He told the New Yorker’s Ronan Farrow that before his 2014 retirement, he’d “served as a chief operations inspector and flight commander with the 706th Fighter Squadron” and during his career had deployed to Afghanistan and Iraq.

“The President asked for his supporters to be there to attend, and I felt like it was important, because of how much I love this country, to actually be there,” he told Farrow, who wrote that Brock “echoed Trump’s baseless claims of election fraud, saying that he derived his understanding of the matter principally from social media.”