The Jan. 6 attack on the U.S. Capitol was either a security failure, an intelligence failure — or both.

How could security forces in the nation's capital be so swiftly and completely overwhelmed by rioters who stated their plans openly on a range of social media sites? President Trump had even tweeted on Dec. 19: "Big protest in D.C. on January 6th. Be there, will be wild!"

Washington, D.C., is known for its multitude of law enforcement agencies — a fact reflected in the agencies involved in security on Jan. 6. The Metropolitan Police Department has jurisdiction on city streets; the U.S. Park Police on the Ellipse, where Trump's rally took place; the U.S. Secret Service in the vicinity of the White House; and the U.S. Capitol Police on the Capitol complex.

And then there is the National Guard. In the 50 states and Puerto Rico, the Guard is under the command of the governor. In Washington, D.C., however, the Guard is under the command of the president, though orders to deploy are typically issued by the secretary of the Army at the request of the mayor. Others weighed in on the use of the Guard on Jan. 6 — but exactly how that decision was made is the subject of debate.

Here is a timeline of events before, during and after the insurrection at the Capitol. We will update it as more details become known.

Late 2020

The Department of Homeland Security produces a threat assessment — but it is an overview, a DHS spokesperson told NPR, focusing on the "heightened threat environment during the 2020-2021 election season, including the extent to which the political transition and political polarization are contributing to the mobilization of individuals to commit violence."

Late December

The New York Police Department sends a packet of material to the U.S. Capitol Police and the Washington Field Office of the FBI. This raw intelligence — bits and pieces of information scraped from various social media sites — indicates that there will likely be violence when lawmakers certify the presidential election on Jan. 6.

But the DHS and the FBI do not create an intelligence report focused specifically on the upcoming pro-Trump rally. That's important because these reports go beyond raw intelligence — they validate information and put it into context which helps local law enforcement develop a plan. These threat assessments or intelligence bulletins are typically written as a matter of course ahead of high-profile events. It's not clear why this didn't happen.

Monday, January 4

The Metropolitan Police Department arrests Enrique Tarrio, leader of the far-right Proud Boys group. He's released the next day and told to leave Washington, after being charged with destruction of property and possession of high-capacity firearm magazines.

The police had noted that D.C. law prohibits anyone from carrying a firearm within 1,000 feet of any First Amendment activity.

U.S. Capitol Police Chief Steven Sund asks permission from House and Senate security officials to request that the D.C. National Guard be placed on standby, in case the protest gets out of control. The Washington Post reports: "House Sergeant at Arms Paul Irving said he wasn't comfortable with the 'optics' of formally declaring an emergency ahead of the demonstration, Sund said. Meanwhile, Senate Sergeant at Arms Michael Stenger suggested that Sund should informally seek out his Guard contacts, asking them to 'lean forward' and be on alert in case Capitol Police needed their help."

Tuesday, January 5

The FBI Field Office in Norfolk, Va. issues an explicit warning that extremists have plans for violence the next day, as first reported by the Post. It releases its advisory report after FBI analysts find a roster of troubling information including specific threats against members of Congress, an exchange of maps of the tunnel system under the Capitol complex, and organizational plans like setting up gathering places in Kentucky, Pennsylvania and South Carolina where extremists can meet to convoy to Washington.

FBI Norfolk shares what they have discovered with counterparts in D.C., the Post reports. The head of the FBI's Washington Field Office, Steven D'Antuono, later says that information is shared with the FBI's "law enforcement partners" through the bureau's Joint Terrorism Task Force. That includes the U.S. Capitol Police, U.S. Park Police, D.C.'s Metropolitan Police Department (MPD) and other agencies.

Officials convene a conference call with local law enforcement to discuss the Norfolk warning. The NYPD and Norfolk information contains raw intelligence that isn't yet validated or analyzed. Sources tell NPR the information was worrisome because of its specificity, but was based on one or two sources — generally not enough to start deploying police or the National Guard.

Washington Mayor Muriel Bowser announces that the MPD will be the lead law enforcement agency and will coordinate with the Capitol Police, Park Police and Secret Service. "To be clear, the District of Columbia is not requesting other federal law enforcement personnel and discourages any additional deployment without immediate notification to, and consultation with, MPD if such plans are underway," Bowser tweets.

In a letter to the Justice Department, Bowser says "we are mindful" of events in 2020 — likely referencing the June 1 clearing of peaceful protesters in Lafayette Square by Park Police and other federal law enforcement not answerable to the city. Police advanced through the crowd with little warning, firing tear gas and smoke canisters shortly before Trump appeared outside for a photograph in front of St. John's Episcopal Church. NPR later reported that Park Police asked the National Guard if they had a "heat ray" weapon they could deploy. The National Guard said no.

That day appears to have profoundly influenced the mayor's approach to Jan. 6. In her letter, Bowser describes the difficulty and confusion of policing large crowds while working around other law enforcement personnel without proper coordination and identification.

Bowser requests, and receives, a limited force from the D.C. National Guard. The soldiers number 340, though they are unarmed and their job is to help with traffic flow — not law enforcement — which is to be handled by D.C. police.

Officials including Chief Sund of the Capitol Police brief U.S. Rep. Zoe Lofgren, D-Calif., the chair of the House Administration Committee. "I was told by the police chief and the sergeant-at-arms that everything is under control and they had provided for every contingency," Lofgren later told The New York Times. "That turned out to be completely false."

Wednesday, January 6

Just before noon Trump begins to address the crowd at the Ellipse, behind the White House. He falsely claims that "this election was stolen from you, from me, from the country."

Trump calls on his supporters at the rally to march on the U.S. Capitol, saying he will walk with them. Instead, he returns to the White House.

Around 1:00 p.m. "We see this huge crush of people coming down Pennsylvania Ave. toward the Capitol," reports NPR's Hannah Allam. "We follow the crowd as it goes up to the Hill, toward the Capitol. There's scaffolding set up for the inauguration already," she adds. "But as far as protection, all we really saw were some mesh barriers, some metal fencing and only a small contingent of Capitol Police. And we watched them being quickly overwhelmed."

The FBI says multiple law enforcement agencies receive reports of a suspected pipe bomb at the headquarters of the Republican National Committee. Fifteen minutes later, there are reports of a similar device at the Democratic National Committee headquarters. The agency offers a $50,000 reward for information.

1:11 p.m. Trump finishes his remarks.

1:34 p.m. Mayor Bowser asks Army Secretary Ryan McCarthy for additional Guard forces, according to a Pentagon timeline.

1:49 p.m. Capitol Police Chief Sund speaks with the commanding general of the D.C. National Guard Maj. Gen. William Walker by phone and requests immediate assistance.

2:00-2:30 p.m. NPR reporter Tom Bowman and producer Graham Smith watch from the Capitol lawn as D.C. police in riot gear move in and out of the crowds.

Moving to the Senate terrace, they see protesters smashing the door of the Capitol to gain entry, as Capitol Police inside work to push them back.

2:10 p.m. Capitol Police send an alert that all buildings in the Capitol complex are on lockdown due to "an external security threat located on the West Front of the U.S. Capitol Building. ... [S]tay away from exterior windows and doors. If you are outside, seek cover."

The House and Senate abruptly go into recess.

2:14 p.m. Demonstrators arrive close to the Senate chamber, as seen on video captured by Huffington Post reporter Igor Bobic. Capitol Police Officer Eugene Goodman redirects them to another hall where there are additional officers.

2:22 p.m. On a conference call with Pentagon officials, D.C. Mayor Bowser requests National Guard support and Capitol Police Chief Sund pleads for backup.

"I am making an urgent, urgent immediate request for National Guard assistance," Sund told The Washington Post he said on the call. "I have got to get boots on the ground."

D.C. officials on the call told the Post they heard director of the Army Staff Lt. Gen. Walter Piatt say that he could not recommend his boss, Army Secretary McCarthy, approve the request and that he did not like "the visual" of a line of National Guard soldiers in front of the Capitol.

Piatt disputes this. He says that McCarthy ran to the office of Acting Defense Secretary Christopher Miller for approval as soon as he had a specific request for assistance from the Capitol Police. Piatt says he told the others on the call that he was not the approval authority, and that they needed to make a plan for how to use the National Guard troops if approved.

2:24 p.m. Trump tweets criticism of Vice President Pence: "Mike Pence didn't have the courage to do what should have been done to protect our Country and our Constitution, giving States a chance to certify a corrected set of facts, not the fraudulent or inaccurate ones which they were asked to previously certify. USA demands the truth!"

2:30 p.m. Acting Defense Secretary Miller, Chairman of the Joint Chiefs of Staff Gen. Mark Milley, and Army Secretary McCarthy meet to discuss the requests from Capitol Police Chief Sund and Mayor Bowser.

2:31 p.m. Bowser orders a citywide curfew beginning at 6 p.m.

2:44 p.m. Reports come from inside the House chamber of an armed standoff at the door to the chamber. Police officers have their guns drawn on someone trying to get in.

A gunshot is heard. A Capitol police officer shoots rioter Ashli Babbitt, an Air Force veteran from the San Diego area, who later dies.

Three other protesters die in the riot from medical emergencies. Capitol Police Officer Brian Sicknick later dies from injuries suffered when he was attacked by rioters. Four days later, Capitol Police Officer Howard Liebengood, who was at the Capitol during the riot, dies by suicide.

3 p.m. Acting Defense Secretary Miller determines that all available forces of the D.C. National Guard are required to reestablish security of the Capitol complex.

Guardsmen are moved from traffic points and Metro stations to the D.C. Armory and refitted for a crowd control mission. Army Secretary McCarthy directs the National Guard to prepare soldiers to move from the Armory to the Capitol complex.

3:04 p.m. Miller provides verbal approval for the full activation of the D.C. National Guard — 1,100 members. McCarthy directs the D.C. National Guard to initiate full mobilization.

3:29 p.m. Virginia Gov. Ralph Northam tweets that his team is working closely with Mayor Bowser, House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer to respond to the situation. Northam says, at the mayor's request, he is sending Virginia National Guard members and 200 Virginia State Police troopers to Washington.

3:26 p.m. McCarthy tells Bowser and D.C. Police Chief Robert Contee that their request was approved.

3:36 p.m. White House press secretary Kayleigh McEnany says on Twitter that the National Guard is on its way at Trump's direction.

4:17 p.m. Trump tweets a video downplaying the events of the day, repeating false claims that the election was stolen and sympathizing with his followers, saying: "I know your pain, I know you're hurt. We had an election that was stolen from us. It was a landslide election and everyone knows it, especially the other side. But you have to go home now. We have to have peace. ... You're very special. You've seen what happens. You see the way others are treated that are so bad and so evil. I know how you feel, but go home, and go home in peace."

5:02 p.m. One hundred fifty-four members of the D.C. National Guard depart the D.C. Armory.

5:21 p.m. In a video statement, Maryland Gov. Larry Hogan says, "I never thought I'd see a day like this in America. All Americans should be outraged by this attack on our nation's Capitol." Hogan gives orders to mobilize 200 Maryland State Police troopers and 500 National Guard troops.

5:40 p.m. NPR's Tom Bowman and Graham Smith see the D.C. National Guard arrive at the East Front of the Capitol with helmets and shields. The area is now lined with D.C. police, Prince George's County (Md.) Police and other law enforcement.

6 p.m. Acting Defense Secretary Miller authorizes the mobilization of up to 6,200 National Guard troops from Maryland, Virginia, New York, New Jersey, Delaware and Pennsylvania, according to the Pentagon.

A curfew begins in Washington.

6:01 p.m. Trump tweets a message to his supporters. "These are the things and events that happen when a sacred landslide election victory is so unceremoniously & viciously stripped away from great patriots who have been badly & unfairly treated for so long. Go home with love & in peace. Remember this day forever!"

6:14 p.m. Capitol Police, MPD and the D.C. National Guard establish a perimeter on the west side of the Capitol.

By 7:15 p.m. "[B]oth chambers and leadership offices were cleared, and members were able to return to business, and we began the planning for the following day," Army Secretary McCarthy later says.

8 p.m.: The Capitol is declared secure. Members of Congress return to complete the opening and counting of the Electoral College.

Thursday, January 7

3:45 a.m. Pence affirms that Joe Biden and Kamala Harris have won the Electoral College: "Joseph R. Biden Jr. of the state of Delaware has received for president of the United States, 306 votes. Donald J. Trump of the state of Florida has received 232 votes."

Later that day: Sund resigns. So do Michael Stenger, the Senate sergeant-at-arms, and Paul Irving, sergeant-at-arms for the House of Representatives.

Acting U.S. Attorney for the District of Columbia Michael Sherwin and the FBI begin to announce a series of arrests and a variety of federal criminal charges against people involved in the Capitol attack.

Sunday, January 10

The FBI formally warns local law enforcement that armed protests are being planned for all 50 statehouses and the U.S. Capitol. The warning says an unidentified group is calling on others to help it "storm" state, local and federal courthouses, should Trump be removed as president before Inauguration Day.

Monday, January 11

Rep. Tim Ryan, D-Ohio, says two Capitol Police officers have been suspended. One of the suspended officers took a selfie with a rioter. The other put on a MAGA hat "and started directing people around," says Ryan. He chairs the House subcommittee investigating police response to the riot and says 10 to 15 other Capitol Police officers are under investigation.

Chad Wolf, acting secretary of the Department of Homeland Security, announces he is stepping down. DHS includes the Secret Service, which will be in charge of security for the inauguration.

Tuesday, January 12

The U.S. Justice Department says it has received more than 100,000 pieces of digital information in response to its call for tips about those responsible for the Capitol riot. The Justice Department says MPD acted on its intelligence to arrest the Proud Boys' Tarrio before the protest, and federal officials interrupted travel of others who planned to go to D.C.

Sherwin says the numbers of arrests will "geometrically increase."

Acting DHS Secretary Peter Gaynor issues a memorandum expanding the period of the 59th Presidential Inauguration National Special Security Event, to begin January 13 and lasting through January 21.

Wednesday, January 13

President Trump is impeached by the House of Representatives for inciting an insurrection.

The secretary of the Army announces that as many as 20,000 National Guard troops are expected to be deployed to D.C. for the inauguration. Some will be armed, while others will have access to their weapons but will not carry them.

Thursday, January 14

FBI Director Christopher Wray says the bureau has identified more than 200 suspects from the Capitol riots and arrested more than 100 others in connection with the violence. "We know who you are if you're out there — and FBI agents are coming to find you," he warns.

NPR's Dina Temple-Raston, Cheryl Corley, Greg Myre, Tom Bowman, Martin Kaste and Domenico Montanaro contributed to this report.

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