WASHINGTON — Top national security officials for President Donald Trump, including his defense secretary, texted war plans for upcoming military strikes in Yemen to a group chat in a secure messaging app that included the editor-in-chief for The Atlantic, the magazine reported in a story posted online Monday. The National Security Council said the text chain “appears to be authentic.”

Trump told reporters he was not aware that the sensitive information had been shared, 2 1/2 hours after it was reported.

The material in the text chain “contained operational details of forthcoming strikes on Iran-backed Houthi-rebels in Yemen, including information about targets, weapons the U.S. would be deploying, and attack sequencing,” editor-in-chief Jeffrey Goldberg reported.

It was not immediately clear if the specifics of the military operation were classified, but they often are and at the least are kept secure to protect service members and operational security. The U.S. has conducted airstrikes against the Houthis since the militant group began targeting commercial and military vessels in the Red Sea in November 2023.

Just two hours after Goldberg received the details of the attack on March 15, the U.S. began launching a series of airstrikes against Houthi targets in Yemen.

The National Security Council Is Looking Into the Matter

The National Security Council said in a statement that it was looking into how a journalist’s number was added to the chain in the Signal group chat.

Trump told reporters, “I don’t know anything about it. You’re telling me about it for the first time.” He added that The Atlantic was “not much of a magazine.”

Government officials have used Signal for organizational correspondence, but it is not classified and can be hacked. Privacy and tech experts say the popular end-to-end encrypted messaging and voice call app is more secure than conventional texting.

The sharing of sensitive information comes as Defense Secretary Pete Hegseth’s office has just announced a crackdown on leaks of sensitive information, including the potential use of polygraphs on defense personnel to determine how reporters have received information.

Sean Parnell, a spokesman for Hegseth, did not immediately respond to requests for comment on why the defense secretary posted war operational plans on an unclassified app.

The breach in protocol was swiftly condemned by Democratic lawmakers. Senate Democratic leader Chuck Schumer called for a full investigation.

“This is one of the most stunning breaches of military intelligence I have read about in a very, very long time,” Schumer, a New York Democrat, said in a floor speech Monday afternoon.

“If true, this story represents one of the most egregious failures of operational security and common sense I have ever seen,” said Sen. Jack Reed of Rhode Island, the top Democrat on the Senate Armed Services Committee, in a statement.

He said American lives are “on the line. The carelessness shown by Trump’s Cabinet is stunning and dangerous. I will be seeking answers from the Administration immediately.”

Rep. Jim Himes of Connecticut, the top Democrat on the House Intelligence Committee, said in a statement that he was “horrified” by the reports.

Himes said if a lower-ranking official “did what is described here, they would likely lose their clearance and be subject to criminal investigation. The American people deserve answers,” which he said he planned to get at Wednesday’s previously scheduled committee hearing.

Senate Majority Leader John Thune said he wants to learn more about what happened.

“Obviously, we got to to run it to the ground, figure out what went on there,” said Thune, a South Dakota Republican.

There Are Strict Laws Around Handling Defense Information

The handling of national defense information is strictly governed by law under the century-old Espionage Act, including provisions that make it a crime to remove such information from its “proper place of custody” even through an act of gross negligence.

The Justice Department in 2015 and 2016 investigated whether former Secretary of State Hillary Clinton broke the law by communicating about classified information with her aides on a private email server she set up, though the FBI ultimately recommended against charges and none were brought.

In the Biden administration, some officials were given permission to download Signal on their White House-issued phones, but were instructed to use the app sparingly, according to a former national security official who served in the Democratic administration.

The official, who requested anonymity to speak about methods used to share sensitive information, said Signal was most commonly used to communicate what they internally referred to as “tippers” to notify someone when they were away from the office or traveling overseas that they should check their “high side” inbox for a classified message.

The app was sometimes also used by officials during the Biden administration to communicate about scheduling of sensitive meetings or classified phone calls when they were outside the office, the official said.

The use of Signal became more prevalent during the last year of the Biden administration after federal law enforcement officials warned that China and Iran were hacking the White House as well as officials in the first Trump administration, according to the official.

The official was unaware of top Biden administration officials — such as Vice President Kamala Harris, Defense Secretary Lloyd Austin and national security adviser Jake Sullivan — using Signal to discuss sensitive plans as the Trump administration officials did.

Some of the toughest criticism targeted Hegseth, a former Fox News Channel weekend host. Sen. Tammy Duckworth, an Iraq War veteran, said on social media that Hegseth, “the most unqualified Secretary of Defense in history, is demonstrating his incompetence by literally leaking classified war plans in the group chat.”