The commanding general of the D.C. National Guard told lawmakers Wednesday that restrictions the Pentagon placed on him in the run-up to the Capitol riot and lag time in decision-making by his chain of command prevented him from more quickly sending forces to help quell the violence.

Maj. Gen. William J. Walker said his hands were tied by the Pentagon for more than three hours after he received a call from the Capitol Police chief saying a request for backup was imminent, delaying the arrival of military forces at the premises as lawmakers evacuated or barricaded themselves in offices during one of the biggest national security failures since the 9/11 attacks.

Walker described how he had troops ready and waiting to be sent to the Capitol but did not have sign-off from the Pentagon, which in directives ahead of the events had restricted his leeway to respond to contingencies.

The quest by lawmakers to understand the failings that led to the Jan. 6 insurrection took on special urgency during the hearing, as the Capitol Police on Wednesday warned of a possible plot by a militant group to breach the Capitol on March 4, a day that some conspiracy theorists have baselessly declared the “true Inauguration Day” when former president Donald Trump will again assume power. Responding to the threat, the House scrapped plans for a Thursday session.

Walker’s testimony, which expanded on comments he first made to The Washington Post in late January, brought the Pentagon back to the center of a furor over the government’s preparations for and response to the Jan. 6 events and increased pressure on Congress to hold a public hearing with the uniformed and civilian leaders who were overseeing the U.S. military from the Pentagon that day.

On Wednesday, their absence was stark.

The Defense Department sent a career official to the hearing, Robert Salesses, who was not one of the main operational decision-makers at the Pentagon on Jan. 6. The top civilian and uniformed leaders who were in charge that day have not testified publicly but have defended their actions in comments to the media. They have described the military’s response as rapid, given that neither the Capitol Police nor any other federal law enforcement agency had requested help from the military in advance and that city officials had asked for Guard troops to assist only with traffic and crowd management.

Much of the hearing before the Senate’s Rules Committee and its Homeland Security and Governmental Affairs Committee focused on how long it took the Pentagon to give the members of the D.C. Guard who were already deployed on Jan. 6 a new mission and send them to the Capitol.

Walker’s comments bolstered critics of the Defense Department who say the U.S. military leadership moved too slowly in getting the National Guard to the Capitol and laid bare the tension between the D.C. Guard and the Pentagon about how the military should have responded.

Walker said he did not receive permission from his chain of command at the Pentagon to send forces to the Capitol until three hours and 19 minutes after receiving an urgent call at 1:49 p.m. Jan. 6 from the Capitol Police chief saying a request for Guard backup was imminent. But the call came only about 25 minutes before rioters breached the building, raising the possibility that the situation was already too far gone by the time the military was summoned.

The acting defense secretary at the time, Christopher C. Miller, activated the full D.C. Guard shortly after 3 p.m. in response to the riot, calling up troops who had not been mobilized, but he did not assign the already deployed members a new mission and send them to the Capitol until 4:32 p.m., according to Salesses. Walker said he did not receive word that he could go to the Capitol until 5:08 p.m., more than half an hour later.

“How is that possible?” Sen. Roy Blunt (R-Mo.) asked incredulously, noting the time gap.

“I think that’s an issue,” Salesses said, offering no explanation.

The Guard arrived at 5:20 p.m.

“It shouldn't take three hours to either say yes or no to an urgent request from either the Capitol Police, the Park Police, the Metropolitan Police Department,” Walker said.

Walker also discussed the restrictions that the Defense Department placed on him in memos issued Jan. 4 and 5 — limits that were first reported by The Post.

In a Jan. 5 memo, then-Army Secretary Ryan McCarthy, Walker’s direct superior in the chain of command, prohibited him from deploying a quick-reaction force composed of 40 soldiers on his own and said any rollout of that standby group would first require a “concept of operation,” an exceptional requirement given that the force is supposed to respond to emergencies.

In the Jan. 4 memo, the Army secretary himself was prohibited from deploying D.C. Guard members with weapons, helmets, body armor or riot control agents without the defense secretary’s approval but retained the power to deploy the quick-reaction force, “only as a last resort.”

Had he not been restricted by Pentagon directives, Walker said, he could have sent about 150 soldiers to aid police at the Capitol within about 20 minutes — a force that may not have changed the outcome of the day, given the lateness of the call for backup, but that Walker said would have helped.

“I believe that number could have made a difference,” Walker said. “We could have helped extend the perimeter and helped push back the crowd.”

He called the memo that restricted him unlike anything he had seen in his career.

“The memo was unusual in that . . . it required me to seek authorization from the secretary of the Army and the secretary of defense to essentially even protect my Guardsmen,” Walker said, referring to restrictions placed on his ability to deploy the 40-person quick-reaction force if members of the Guard deployed for the traffic and crowd-control mission that day had ended up in distress.

Because the District of Columbia is not a state, the D.C. Guard answers to the president, but that authority is delegated to the defense secretary and the Army secretary, who oversee the force.

Asked during the hearing why the Pentagon put those restrictions in place ahead of Jan. 6, Salesses said they were the result of heavily criticized actions the military took in D.C. in response to racial-injustice protests last year — and a desire by Miller, who had just arrived at the Pentagon as acting secretary, to keep tight reins on any operations as a result.

“There was a number of incidents . . . where we had helicopters flying above U.S. citizens, we had spy planes, RC-26s, flying over folks who were protesting,” Salesses said. “We also had law enforcement officers that were in military uniforms, which sometimes confused people. So when the new secretary came in, he wanted to make sure that he had guidance on making decisions.”

Salesses pointed to a letter that D.C. Mayor Muriel E. Bowser (D) sent to the Pentagon and Justice Department confirming that she did not want or need any more federal officials apart from the Guard members being deployed for the limited traffic and crowd-control mission. He said the Defense Department had reached out to all the other federal law enforcement agencies, including the Capitol Police, to ask whether they needed military assistance in the run-up to the event — and was told no.

Miller, who served as acting defense secretary for 2 1/2 months, has rejected criticism that the Pentagon was too slow in responding to the riot, saying in an interview with Vanity Fair that any suggestion the Defense Department dragged its feet “is complete horse----.” He said the Pentagon leadership “had their game together.”

Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff, said in remarks to reporters this week that the Defense Department reacted at “sprint speed,” seeing as the military had not been asked to prepare contingency forces in advance and still got to the scene within hours.

Lawmakers at the hearing Wednesday disagreed.

“The three-hour-and-19-minute delay in authorizing the deployment of the National Guard to respond to the Capitol to quell the violence was one that left police, members of Congress, staff and the public in danger and is without question completely unacceptable,” Sen. Gary Peters (D-Mich.), chairman of the Senate Homeland Security and Governmental Affairs Committee, said at the conclusion of the hearing.

During the hearing, Walker also addressed a call on the afternoon of Jan. 6, during which he said top Army generals expressed reluctance to deploy the National Guard to the Capitol due to the optics, shocking him and officials from the Capitol Police, D.C. police and the D.C. government on the call.

Asked about those comments, Walker said they were made by Lt. Gen. Walter E. Piatt, the director of the Army staff, and Lt. Gen. Charles A. Flynn, the Army’s deputy chief of staff for operations and the brother of former White House national security adviser Michael Flynn.

“They both said it wouldn’t be in their best military advice to advise the secretary of the Army to have uniformed Guardsmembers at the Capitol during the election confirmation,” Walker said.

Piatt initially denied making those comments but later told reporters he “may have said that,” though he said he did not recall using the word “optics.” Charles Flynn has said he does not remember whether he said anything during the call. He has said his relationship with his brother, who had been floating martial law and calling for the military to “rerun” the election ahead of the riot, had no impact on his actions.

Salesses said during the hearing that Piatt told him he never made those comments.

Neither Piatt nor Flynn was in the chain of command, and therefore they were not empowered to deploy the Guard to the Capitol or deny a deployment. Piatt has said he was attempting to talk through how the Guard deployment would work with the officials on the call, as the Army secretary ran down the hall to receive sign-off from the acting defense secretary to activate the Guard.

As the hearing homed in on the Pentagon’s response, Sen. Rand Paul (R-Ky.) suggested the lawmakers should focus on the police preparation rather than the Defense Department, given that the Capitol Police, which answers to Congress and is responsible for securing the Capitol, did not have its full force on duty the day of the riot.

“It isn’t about calling the National Guard out quicker. It’s about having a thousand people standing there before the riot happens so the riot doesn’t happen,” Paul said, adding, “I think we can get too bogged down on the details of January 6th and forget about what could have actually fixed this.”

Officials from virtually all federal law enforcement and defense agencies have faced criticism for miscalculating the possibility that Trump supporters who came to D.C. for a rally Jan. 6 could turn violent and set their sights on the Capitol, where lawmakers were counting the electoral-college votes. In addition to congressional inquiries, the inspectors general of several federal agencies are investigating officials’ response.

During the hearing, Melissa Smislova, a senior official in the Department of Homeland Security’s Office of Intelligence and Analysis, candidly conceded that DHS was “completely dissatisfied with the result of our efforts leading up to January 6th.”

“We thought that it was sufficient, and clearly it was not,” she said.

Smislova said that ahead of the events, DHS had produced 15 unclassified assessments that discussed “the heightened threat environment” and the potential for extremists to attack large gatherings or government buildings. She said the department is now reassessing how it presents and distributes those reports.

Jill Sanborn, the FBI’s assistant director for counterterrorism, sought to downplay a Jan. 5 report from the Norfolk field office warning of violence at the Capitol — a warning that the chief of the D.C. police said no one called him about.

Sanborn said the report detailed “raw” and “unvetted” information and was shared quickly with the FBI’s Washington field office only because the bureau had made it a priority to collect intelligence having to do with possible violence surrounding the planned congressional action on Jan. 6. Sanborn said she was not briefed on the report, adding: “Thousands and thousands of tips come in just like this on every day. And not all of those get elevated to senior leadership.”

Sen. Maggie Hassan (D-N.H.) suggested the response left her unsatisfied.

“This was tips about violence at the United States Capitol, where we were going to have all members of Congress, the current vice president, the vice president-elect,” Hassan said. “And so given the gravity of the threat, it is very hard for me to understand why somebody didn’t pick up the phone.”