Military investigating whether service members participated in US Capitol assault

The military services are looking into whether any active-duty military personnel may have participated in the assault on the U.S. Capitol last week. The stunning events at the Capitol prompted the Joint Chiefs of Staff to issue an internal memo to all service members condemning the riot, confirming that Joe Biden will be the next commander in chief and noting that any act to disrupt the Constitutional process is "against the law."

Fort Bragg officials are reviewing an Army officer's claims that she only participated in the rally prior to the violence at the Capitol building and are also trying to determine if other base personnel joined her as part of a group that came to Washington, said a defense official. The psychological operations officer has acknowledged leading a group of 100 North Carolina residents to the rally.

U.S. military personnel are allowed to participate in political events as long as they do so on their own time and are not in military uniform.

A service member's participation in the rally or march that preceded the assault on the U.S. Capitol would fall into that category. However, the military services will look at whether any military personnel played a role in the security breach at the Capitol building and any of the violent events, which could result in disciplinary action.

Several individuals arrested at the Capitol were veterans who had once served in the military, but an ABC News review of records shows none of them is currently serving in the military.

The violence prompted America's top military leaders to issue an internal memo reminding troops that they are sworn to protect the Constitution and that on on Jan. 20, Biden will become the next commander in chief.

"The violent riot in Washington D.C. on January 6, 2021 was a direct assault on the U.S. Capitol building, and our Constitutional process," said the memo, signed by all the members of the Joint Chiefs of Staff.

"We witnessed actions inside the Capitol building that were inconsistent with the rule of law," the memo added. "The rights of freedom of speech and assembly do not give anyone the right to resort to violence, sedition and insurrection."

"We support and defend the Constitution," it said. "Any act to disrupt the Constitutional process is not only against our traditions, values, and oath; it is against the law," it continued.

On Monday, Sen. Tammy Duckworth, D- Ill., sent a letter to acting Defense Secretary Chris Miller requesting that Defense Department's criminal investigative organizations work with the FBI and Capitol Police to investigate current and retired military who may have participated in the assault. And if any service members did participate in the events at the Capitol, she urged Miller "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," wrote Duckworth.

Jonathan Hoffman, the Pentagon's top spokesman, said on Monday that the Pentagon's stance has always been to not tolerate extremists in the ranks.

"Any effort, any opportunity we have to identify individuals that have extremist behavior issues, tendencies they will be addressed," said Hoffman. "They will be referred to appropriate authorities for addressing that."

Contacted by ABC News, the four military services said they were already cooperating with law enforcement or preparing to do so to determine if any of their service members were at the Capitol.

"NCIS (Naval Criminal Investigative Service) is coordinating closely with our federal law enforcement partners to determine if any DON-affiliated personnel participated in criminal activity at the Capitol Jan. 6, 2021," said a statement provided to ABC News by the Navy and the Marine Corps.

The Air Force said its Office of Special Investigations is "ready to assist civilian law enforcement in any investigations into suspected violators of the law."

"There is no place for extremism in our ranks. If we find case of extremism we will investigate each case and hold people appropriately accountable, said an Army official.

At Fort Bragg in North Carolina, the Army has confirmed that it is reviewing Capt. Emily Rainey's participation at the rally at the Ellipse.

"Our command is aware of Capt. Emily Rainey's presence at the Capitol on Jan. 6 and is currently investigating to determine the facts as to her exact involvement," said Maj. Dan Lessard, a spokesperson for 1st Special Forces Command (Airborne).

"It is unclear if she violated any laws or regulations, as the DoD encourages members of the Armed Forces to carry out the obligation of citizenship, so long as their actions are in keeping with DoD policy and do not impair the good order and discipline of the service," said Lessard.

The investigation will determine whether further actions by the command are warranted.

"I was a private citizen and doing everything right and within my rights," Rainey told The Associated Press on Sunday.

The Army is reviewing whether any of the other people in Rainey's group were also active-duty personnel stationed at the base, said a defense official.

Meanwhile, concerns about the possibility that military service members may have participated in the violence has led to an extraordinary outreach to veterans made by Capitol Hill officials.

Prominent veterans have been asked to issue statements that would dissuade service members from participating in protests surrounding the upcoming presidential inauguration.

"As members of the military, we fought to defend our constitutionally guaranteed right to free speech. But the attack against the U.S. Capitol on January 6th was not about free speech, it was an insurrection," Mick Mulroy and Eric Oehlerich said in a joint statement. Mulroy, a retired Marine, and Oehlerich, a retired Navy SEAL, are both ABC News contributors.

"Any military member who participated violated their oath to defend the United States' Constitution -- against all enemies, foreign and domestic," they wrote.

"As veterans, we must unite around the values and the principles for which our nation stands," the statement continued. "Together, we must condemn those who have violated their oath to defend our nation. While we may have political disagreements, we must defend our democracy."