The Trump administration is under scrutiny after The Atlantic editor Jeffrey Goldberg said he was inadvertently added to a Signal group chat that included top national security officials, including Defense Secretary Pete Hegseth, in which the officials discussed plans for a U.S. attack on Houthis in Yemen.

Goldberg revealed the mishap in a piece for the magazine on Monday and told ABC News that he was apparently added to the chat by National Security Adviser Mike Waltz.

Goldberg provided two screenshots in the magazine piece and did not provide details or quotes, only a description of the operational part of the Signal message chain.

Both the Trump administration and top officials involved have repeatedly denied that war plans or classified information were discussed, as Goldberg reported.

Below is a timeline spanning from the creation of the group chat to what has happened since.

March 11

In an interview with "ABC News Live" Monday evening, Goldberg told Linsey Davis he received a message request on the Signal app from White House national security adviser Mike Waltz, or someone "who's purporting to be Mike Waltz" on March 11.

He said the invitation was "not an unusual thing in Washington."

"I'm a journalist, I've met him in the past, so I accept it," he told ABC News.

Goldberg said he accepted the request, with nothing occurring until several days later, when he was added to a "group of seemingly very high national security officials of the United States" including Vice President JD Vance, with Waltz apparently creating this chat.

"Mike Waltz puts this group together and says it's a planning group for essentially upcoming action in Yemen," Goldberg said.

Goldberg told ABC News he initially thought it was a hoax since it would be "completely absurd to me that the national security leadership of the United States would be meeting on a messaging app to discuss forthcoming military action, and that then they would also invite the editor of The Atlantic magazine to that conversation."

March 14

Goldberg told ABC News a "long conversation" occurred between the group chat members on March 14, discussing "whether or not they should or shouldn't take action in Yemen."

The messages went back and forth with "a lot of resentment directed at European allies of the United States, which obviously enhanced the credibility of this chain," Goldberg said.

He told ABC News at this point the members of the chat sounded like people he knew within the administration, but was still not sure whether or not it was a hoax.

March 15

Goldberg told ABC News he continued to track the incoming messages from the group chat, to see "who was trying to entrap me or trick me." Then on March 15, he said it became "overwhelmingly clear" it was a legitimate group chat, he told ABC News.

At 11:44 a.m., he said he received a text in the chain from someone claiming to be Hegseth, or "somebody identified as Pete," providing what Goldberg characterized as a war plan. The message included a "sequencing of events related to an upcoming attack on Yemen" and promised results by 1:45 p.m. Eastern time.

Goldberg told ABC News he was in his car and waiting with his phone to "see if this was a real thing."

"Sure enough, around 1:50 [p.m.] Eastern time, I see that Yemen is under attack," he said.

When the attacks seemed to be "going well," Goldberg told ABC News that members of the chat began sending congratulatory messages along with fist, fire and American flag emojis.

"That was the day I realized this is possibly unbelievably the leaders of the United States discussing this on my messaging app," Goldberg told ABC News. "My reaction was, I think I've discovered a massive security breach in the United States national security system."

Goldberg told ABC News he removed himself from the group chat once the operation was completed.

"I watched this Yemen operation go from beginning to apparent end, and that was enough for me to learn that there's something wrong in the system here that would allow this information to come so dangerously close to the open wild," Goldberg said.

March 16

Waltz appeared on ABC's "This Week" the day after the strikes on Yemen and said the U.S. airstrikes "took out" multiple leaders of the Iranian-backed Houthis, which he said differed from the Biden administration's launches against the group.

"These were not kind of pinprick, back and forth — what ultimately proved to be feckless attacks," Waltz said. "This was an overwhelming response that actually targeted Houthi leaders and took them out. And the difference here is, one, going after the Houthi leadership, and two, holding Iran responsible."

March 24

Goldberg published a story in The Atlantic revealing the mishap, in a piece titled "The Trump Administration Accidentally Texted Me Its War Plans."

Shortly after the story's publication on Monday afternoon, White House National Security Council spokesman Brian Hughes shared with ABC News the statement he provided to The Atlantic confirming the authenticity of the Signal group chat.

"At this time, the message thread that was reported appears to be authentic, and we are reviewing how an inadvertent number was added to the chain. The thread is a demonstration of the deep and thoughtful policy coordination between senior officials. The ongoing success of the Houthi operation demonstrates that there were no threats to our servicemembers or our national security," Hughes said in a statement.

Speaking to reporters Monday, Hegseth denied he sent war plans in the chat.

"I've heard how it was characterized. Nobody was texting war plans, and that's all I have to say about that," Hegseth told reporters in Honolulu while on a layover on his trip to Asia.

Hegseth called Goldberg a "deceitful and highly discredited, so-called journalist who's made a profession of peddling hoaxes time and time again."

"This is the guy that pedals in garbage. This is what he does," Hegseth said about Goldberg.

During an event at the White House on Monday, President Donald Trump was asked about Goldberg's article. "I don't know anything about it. I'm not a big fan of The Atlantic," he said.

Top Democrats including House Minority Leader Hakeem Jeffries voiced outrage at the administration after this mishap.

"It is yet another unprecedented example that our nation is increasingly more dangerous because of the elevation of reckless and mediocre individuals, including the Secretary of Defense," Jeffries said in a statement on Monday.

Former Secretary of State Hillary Clinton, who faced scrutiny over her alleged use of a private email server while at the State Department, shared her reaction to the Signal group chat on X: "You have got to be kidding me."

Senate Minority Leader Chuck Schumer also criticized this apparent breach of military intelligence, urging Senate Republicans to work with Democrats in a "full investigation" to look into how this incident occurred.

"If you were up in arms over unsecure emails years ago, you should certainly be outraged by this amateurish behavior," Schumer said on the Senate floor, referencing the scandal over Clinton's emails.

March 25

On Tuesday morning, White House Press Secretary Karoline Leavitt said Goldberg is "well-known for his sensationalist spin" and emphasized that "no 'war plans' were discussed."

"As the National Security Council stated, the White House is looking into how Goldberg's number was inadvertently added to the thread. Thanks to the strong and decisive leadership of President Trump, and everyone in the group, the Houthi strikes were successful and effective. Terrorists were killed and that's what matters most to President Trump," Leavitt shared on X.

Trump told NBC News he remains confident in Waltz even after the use of an unsecured group chat.

"Michael Waltz has learned a lesson, and he's a good man," Trump told NBC correspondent Garrett Haake.

Director of National Intelligence Tulsi Gabbard and CIA Director John Ratcliffe were grilled by Democratic Sen. Mark Warner on Tuesday regarding the mishap. Both officials said while testifying before the Senate Select Committee on Intelligence there was no classified information on the chain.

Ratcliffe said he believed the "national security adviser intended this to be as it should have been, a mechanism for coordinating between senior level officials, but not a substitute for using high side or classified communications for anything that would be classified."

Speaker Mike Johnson continued to downplay the mishap but admitted the breach was a "serious" mistake on Tuesday.

"Look, they have acknowledged that there is an error, and they are correcting it. And I would've asked the same thing of the Biden administration," Johnson said during a news conference Tuesday morning.

During a White House meeting with ambassadors on Tuesday afternoon, Trump said this incident is "just something that can happen" and that there was "no classified information" in the group chat.

He added that Signal is "not a perfect technology."

"Sometimes somebody can get onto those things," Trump said. "That's one of the prices you pay when you're not sitting in the Situation Room with no phones on, which is always the best, frankly."

Waltz said the White House's tech and legal teams are looking into the mishap.

"No one in your national security team would ever put anyone in danger," Waltz said.

He also claimed to have never met Goldberg.

"We are looking into him, reviewing how the heck he got into this room," Waltz said.

A spokesperson for The Atlantic released a statement on Tuesday night following the comments from Trump and his aides.

"Attempts to disparage and discredit The Atlantic, our editor and our reporting follow an obvious playbook by elected officials and other in power who are hostile to journalists and the First Amendment rights of all Americans," the magazine said.

The statement went on to say that "any responsible national security expert would consider the information contained in this Signal chat to be of the greatest sensitivity, and would agree that this information should never be shared on non-government messaging apps."

On Tuesday night, Waltz said he was the one responsible for what took place.

"I take full responsibility. I built the group," Waltz told Fox News' Laura Ingraham.

At the same time, Waltz tried to flip the script and blame Goldberg — suggesting the editor could have somehow wormed his way in to the group chat.

"Of course, I didn't see this loser in the group. It looked like someone else. Now, whether he did it deliberately or it happened in some other technical mean, is something we're trying to figure out," Waltz said, without evidence, on Fox News.

March 26

Schumer and other top Senate Democrats on national security committees wrote a letter to Trump seeking more information about the mishap, requesting a "complete and unredacted" transcript of the Signal group chat for the appropriate committees to review in a secure setting.

"We write to you with extreme alarm about the astonishingly poor judgment shown by your Cabinet and national security advisors," the Senators wrote, according to a copy of the letter obtained by ABC News. "You have long advocated for accountability and transparency in the government, particularly as it relates to the handling of classified information, national security and the safety of American servicemembers. As such, it is imperative that you address this breach with the seriousness and diligence that it demands."

The Atlantic on Wednesday published a new article detailing purported information about recent American strikes in Yemen it says was accidentally shared in the Signal group chat.

The article suggested that Hegseth updated members of the "Houthi PC small group" Signal chat on "favorable" weather conditions ahead of planned airstrikes on Houthi leaders and other targets in Yemen.

The article said Hegseth also notified the group of a planned timeline for flights of F-18 strike aircraft, MQ-9 Reaper drones and Tomahawk cruise missiles that were launched for the mission.

Shortly after the article was published, Leavitt said in a post on X "these were NOT 'war plans.'"

"This entire story was another hoax written by a Trump-hater who is well-known for his sensationalist spin," the White House press secretary said.

Waltz said Wednesday morning that the chat didn't include war plans or specific details about the strike.

"No locations. No sources & methods. NO WAR PLANS. Foreign partners had already been notified that strikes were imminent. BOTTOM LINE: President Trump is protecting America and our interests," Waltz posted on X.

Also on Wednesday, U.S. District Judge James Boasberg was assigned to a federal lawsuit against five Cabinet members over the administration's use of Signal. Boasberg is also handling the case against the Trump administration over its deportation flights under the Alien Enemies Act.

The lawsuit — which names Hegseth, Gabbard, Ratcliffe, Treasury Secretary Scott Bessent, Secretary of State Marco Rubio and the National Archives as defendants — asked a federal judge to declare the use of Signal unlawful and order the cabinet members to preserve the records immediately.

"Nobody's texting war plans," Hegseth said on Wednesday. "I noticed this morning out came something that doesn't look like war plans. And as a matter of fact, they even changed the title to attack plans because they know it's not war plans."

"It's very clear Goldberg oversold what he had," Vance posted to X.

Goldberg, during an interview with ABC News Live anchor Kyra Phillips, responded to the administration pushback.

"They have decided obviously, instead of simply saying, 'Yeah we had a security breach and we're going to try to plug that breach and do better next time,' they've decided to blame the guy who they invited into the conversation," Goldberg said.

March 27

On Thursday, Judge Boasberg ordered the top cabinet officials named in a lawsuit by the government transparency group American Oversight to retain any messages sent and received over Signal between March 11 and March 15.

Benjamin Sparks, a lawyer representing American Oversight, raised concerns that the messages are in "imminent danger of destruction" due to settings within Signal that can be set to delete messages automatically — prompting Boasberg to order the Trump administration to file a sworn declaration by this Monday to ensure the messages are preserved.

The judge declined, for now, to order administration officials to disclose if Signal had been used by the Trump administration in a wider context.

April 20

Much of the same content shared in the original chat was also shared in a second Signal chat that included Hegseth's wife, his brother and his personal lawyer, two sources familiar with the contents of the chat told ABC News.

Those details shared in the second chat included flight schedules for the F/A-18 Hornets involved in the pending attack on Houthi positions, according to officials. The New York Times was first to report Hegseth's sharing of the details in a second Signal group.

Much of the same content was shared in the second encrypted chat, a group that Hegseth created on his personal phone during his confirmation process, the two officials told ABC News.

Sean Parnell, chief spokesperson for the Pentagon, responded to reports of the second chat in a statement on X on Sunday night, saying in part, "Another day, another old story — back from the dead. The Trump-hating media continues to be obsessed with destroying anyone committed to President Trump's agenda."

The statement continued, "There was no classified information in any Signal chat, no matter how many ways they try to write the story. What is true is that the Office of the Secretary of Defense is continuing to become stronger and more efficient in executing President Trump's agenda."

Sources confirmed with ABC News that the second known Signal chat was originally created to discuss scheduling and administrative information.

April 21

Hegseth did not explicitly deny the report of a second Signal chat when asked by reporters at the White House Easter Egg Roll.

"They take anonymous sources from disgruntled former employees, and then they try to slash and burn people and ruin their reputations. Not going to work with me, because we're changing the Defense Department, putting the Pentagon back in the hands of war fighters and anonymous smears from disgruntled former employees on old news doesn't matter," he said.

Trump defended Hegseth and said he still has "great confidence" in him.

"Here we go again. Just a waste of time. He is doing a great job," Trump told reporters at the White House.

"Ask the Houthis how he's doing," the president said about Hegseth.

The use of Signal to discuss sensitive military operations may complicate ongoing investigations into potential leaks involving the first known group chat, which included top aides and other members of Hegseth's team — at least three of whom have been since fired in relation to the inquiry.

Those officials — Dan Caldwell, Colin Carroll and Darin Selnick — have since spoken out against what they say are baseless accusations against them.

ABC News' Peter Charalambous, Fritz Farrow, Anne Flaherty, Katherine Faulders, Luis Martinez, Isabella Murray, Allison Pecorin, Lauren Peller, Olivia Rubin, Michelle Stoddart, Selina Wang and Kelsey Walsh contributed to this report.