Donald Trump’s national security adviser Mike Waltz included a journalist in the Signal group chat about plans for US strikes in Yemen after he mistakenly saved his number months before under the contact of someone else he intended to add, according to three people briefed on the matter.

The mistake was one of several missteps that came to light in the White House’s internal investigation, which showed a series of compounding slips that started during the 2024 campaign and went unnoticed until Waltz created the group chat last month.

Trump briefly considered firing Waltz over the episode, more angered by the fact that Waltz had the number of Jeffrey Goldberg, the editor of the Atlantic – a magazine he despises – than the fact that the military operation discussion took place on an unclassified system like Signal.

But Trump decided against firing him in large part because he did not want the Atlantic and the news media more broadly to have the satisfaction of forcing the ouster of a top cabinet official weeks into his second term. Trump was also mollified by the findings of the internal investigation.

The disclosures nonetheless triggered a “forensic review” by the White House information technology office, which found that Waltz’s phone had saved Goldberg’s number as part of an unlikely series of events that started when Goldberg emailed the Trump campaign last October.

According to three people briefed on the internal investigation, Goldberg had emailed the campaign about a story that criticized Trump for his attitude towards wounded service members. To push back against the story, the campaign enlisted the help of Waltz, their national security surrogate.

Goldberg’s email was forwarded to then-Trump spokesperson Brian Hughes, who then copied and pasted the content of the email – including the signature block with Goldberg’s phone number – into a text message that he sent to Waltz, so that he could be briefed on the forthcoming story.

Waltz did not ultimately call Goldberg, the people said, but in an extraordinary twist, inadvertently ended up saving Goldberg’s number in his iPhone – under the contact card for Hughes, now the spokesperson for the national security council.

A day after that Goldberg story was published, on 22 October, Waltz appeared on CNN to defend Trump. “Don’t take it from me, take it from the 13 Abbey Gate Gold Star families, some of whom stood on a stage in front of a 30,000 person crowd and said how he helped them heal,” Waltz said.

According to the White House, the number was erroneously saved during a “contact suggestion update” by Waltz’s iPhone, which one person described as the function where an iPhone algorithm adds a previously unknown number to an existing contact that it detects may be related.

The mistake went unnoticed until last month when Waltz sought to add Hughes to the Signal group chat – but ended up adding Goldberg’s number to the 13 March message chain named “Houthi PC small group”, where several top US officials discussed plans for strikes against the Houthis.

Waltz said in the immediate aftermath of the incident that he had never met or communicated with Goldberg. He also suggested on Fox News that Goldberg’s number had been “sucked” into his phone, seemingly in reference to how his iPhone had saved Goldberg’s number.

The White House did not comment on this story, and the investigation did not resolve the extent of Waltz’s relationship with Goldberg, if any. Reached by phone on Saturday, Goldberg said: “I’m not going to comment on my relationship with Mike Waltz beyond saying I do know him and have spoken to him.”

Trump was briefed on the findings of the forensic review last week around the time he decided to keep Waltz, a person familiar with the matter said. Trump accepted Waltz’s mea culpa and has publicly defended him in recent weeks since the group chat situation became public.

When Trump left the White House on Thursday, he was joined aboard Marine One by his chief of staff Susie Wiles, his personnel chief Sergio Gor and Waltz, which aides took as a show of support for the embattled national security adviser.

Waltz also appears to have also engendered some sympathy from inside Trump’s orbit over the group chat because the White House had authorized the use of Signal, largely because there is no alternative platform to text in real time across different agencies, two people familiar with the matter said.

Previous administrations, including the Biden White House, did not develop an alternative platform to Signal, one of the people said. As a temporary solution, the Trump White House told officials to use Signal as they had done during the transition instead of regular text-message chains.