Then-Army Secretary Ryan McCarthy made multiple false claims, including that he spoke to the commanding general of the District of Columbia National Guard on two separate occasions after officials requested that the Guard be deployed to the Capitol, the whistleblowers said.

After Maj. Gen. William Walker conveyed a request from the U.S. Capitol Police for Guard personnel, Mr. McCarthy called Maj. Gen. Walker at 2:14 p.m. and instructed the Guard to stand by, according to a Guard timeline of Jan. 6, 2021. But that call and others that Mr. McCarthy or one of his top advisers were said to have made later authorizing the Guard for mobilization and deployment did not happen, according to the Guard officials.

"At no time did Gen. Walker take any calls, nor did we ever hear from the secretary on any of the ongoing conference calls or the secure video teleconferencing throughout the day," Capt. Timothy Nick, who served as Maj. Gen. Walker's personal assistant on Jan. 6, 2021, said during the hearing. "This I know because I was with the command general the entire time recording the events."

Capt. Nick has not previously discussed publicly what transpired on Jan. 6, 2021, and neither has Brig. Gen. Aaron Dean, who was the National Guard's adjutant general on the day that the Capitol was breached.

The Department of Defense (DOD) inspector general report on Jan. 6, 2021, which relied heavily on Mr. McCarthy and other military officials, was rife with "inaccuracies," Brig. Gen. Dean said. "I believe it is my duty and moral obligation to stand before you today and illuminate the truth," he told the hearing, which was held by the House Administration Committee's Subcommittee on Oversight.

Despite Mr. Walker conveying the request for assistance at about 1:50 p.m., the Guard was not deployed to the Capitol until about 5:10 p.m.

"This was a dereliction of duty by the secretary of the Army," Rep. Greg Murphy (R-N.C.), one of the members of the committee, said.