A journalist was mistakenly added to an encrypted group chat with top officials from US President Donald Trump's administration, where confidential military plans to strike Houthi targets in Yemen were being discussed.
Trump launched an ongoing campaign of large-scale military strikes against , and he warned Iran, the Houthis' main backer, that it needed to immediately halt support for the group.
These attacks began just two hours after the journalist received the information.
The move has been criticised by Democrats, with some calling it "blatantly illegal" and demanding a formal investigation.
What happened?
Jeffrey Goldberg, editor-in-chief of The Atlantic, said he was accidentally added to a Signal messaging app titled 'Houthi PC Small Group' on 13 March.
The group, Goldberg claims, included high-level officials from the Trump administration who were discussing an imminent military strike.
The Signal group appeared to include 18 senior figures, including US vice president JD Vance, defence secretary Pete Hegseth, secretary of state Marco Rubio, Central Intelligence Agency director John Ratcliffe, national intelligence director Tulsi Gabbard, treasury secretary Scott Bessent, White House chief of staff Susie Wiles, an unnamed active intelligence officer, and other senior National Security Council officials.
In a piece from The Atlantic titled The Trump Administration Accidentally Texted Me Its War Plans, Goldberg wrote about his experience in the chat and included screenshots.
According to Goldberg, the messages shared top-secret operational plans to strike Houthi targets, "including information about targets, weapons the US would be deploying, and attack sequencing". He said national security adviser Michael Waltz tasked his deputy, Alex Wong, with forming a "tiger team" to coordinate the operation.
Goldberg said he questioned the chat's legitimacy until what he read turned into reality, with airstrikes launched just two hours after he received details of the attack.
National Security Council spokesperson Brian Hughes said the chat group appeared to be authentic.
Under US law, it can be a crime to mishandle, misuse, or abuse classified information.
Messages that The Atlantic report said were sent by Waltz to disappear from the Signal app after a period of time also raise questions about potential violations of federal record-keeping laws.
What did the messages say?
The chat included more than just military coordination. Some messages were said to reflect an internal debate about whether to carry out the strike at all.
What appeared to be a message from Vance expressed concern about the rationale and timing: "Three per cent of US trade runs through the Suez [Canal]. Forty per cent of European trade does. There is a real risk that the public doesn't understand this or why it's necessary. The strongest reason to do this is, as POTUS said, to send a message."
In another message, the Vance account questioned Trump's broader strategy: "I am not sure the president is aware how inconsistent this is with his message on Europe right now … there is a strong argument for delaying this a month, doing the messaging work on why this matters, seeing where the economy is."
The discussion also showed debates about whether allies in Europe deserved US help.
"@PeteHegseth, if you think we should do it, let's go," a person identified as Vance wrote. "I just hate bailing Europe out again," the person wrote, adding: "Let's just make sure our messaging is tight here."
A person identified as Hegseth replied: "VP: I fully share your loathing of European free-loading. It's PATHETIC."
Goldberg did not publish the most sensitive details but described the exchange as a "shockingly reckless" use of a messaging app to share national security plans.
What has the reaction been?
The incident has raised serious concerns about how the Trump administration handles classified information and if it's complying with security protocols. There are also concerns it could be a violation of the US Espionage Act.
Democratic leaders have condemned the incident, calling for an investigation.
Former Democratic presidential candidate Hillary Clinton expressed her shock in a post on X.
"You have got to be kidding me," she wrote, along with an eyes emoji and a screenshot of the headline and first paragraph of The Atlantic article.
Clinton's use of a private server for classified emails during her time as secretary of state under then-president Barack Obama was a key issue in the 2016 campaign.
"This is one of the most stunning breaches of military intelligence that I have read about in a very, very long time," Senate Democratic leader Chuck Schumer said, adding he would ask majority leader John Thune to investigate.
Democratic senator Elizabeth Warren said on X the use of Signal to discuss highly sensitive national security issues was "blatantly illegal and dangerous beyond belief".
Democratic senator Chris Coons said on X: "Every single one of the government officials on this text chain have now committed a crime — even if accidentally — that would normally involve a jail sentence."
Trump told reporters on Wednesday AEDT that he was unaware of the incident: "I don't know anything about it. I'm not a big fan of The Atlantic," he said.
A White House official later confirmed Trump had since been briefed and an internal investigation was underway.
Despite the backlash, Hughes defended the chat, calling it a "demonstration of the deep and thoughtful policy co-ordination between senior officials".
"The ongoing success of the Houthi operation demonstrates that there were no threats to our servicemembers or our national security," he said, adding that "nobody was texting war plans".
Goldberg responded to that statement in an interview with CNN: "No, that's a lie. He was texting war plans."
— With additional reporting from the Australian Associated Press and Reuters news agency.
