The use of an encrypted, commercial messaging app to discuss plans for U.S. military strikes in Yemen by top Trump administration officials, including Defense Secretary Pete Hegseth, represents a significant security breach that could have endangered the service members involved in the operation, experts and lawmakers said Tuesday.

“There are people whose lives are literally on the line, whether that’s service personnel, whether that’s intelligence personnel,” Michael Williams, an expert on international relations and a professor at Syracuse University, told Military.com in an interview Tuesday. “These guys are supposed to be leaders of the free world, the responsible leaders of the military, the greatest country in the world, and they can’t perform basic operational security.”

The Atlantic reported Monday that several Cabinet members, including Hegseth, National Security Adviser Mike Waltz, Vice President JD Vance, CIA Director John Ratcliffe, Director of National Intelligence Tulsi Gabbard and Secretary of State Marco Rubio, were part of a group chat on the app Signal, where they conferred about plans for then-upcoming strikes against Yemen’s Houthi rebels. The magazine found out because Waltz added its editor-in-chief, Jeffrey Goldberg, to the chat, apparently by accident.

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On the morning of the strikes, Hegseth sent a message to the group that included “operational details of forthcoming strikes on Yemen, including information about targets, weapons the U.S. would be deploying, and attack sequencing,” Goldberg reported. Goldberg did not disclose the specific information in Hegseth’s message or publish screenshots of that portion of the chat, citing the sensitive nature of the information.

While the administration has confirmed the authenticity of the Signal chat, officials are denying that any classified information was shared. Still, they have not directly denied the allegations that specific operational details were sent in the chat.

Military.com asked Hegeseth’s office whether he declassified the information he put onto the chat before sharing it but did not receive a response in time for publication.

Experts who spoke with Military.com on Tuesday said it’s highly unlikely that operational details at the level Goldberg described would not be classified. And, they added, sharing the information outside of classified systems is incredibly irresponsible.

“It’s an extraordinary departure from how we deal with classified information,” Eric Carpenter, a law professor at the Florida International University College of Law and a former Army judge advocate, told Military.com in a phone interview Tuesday.

Carpenter added that, if a service member were to do something similar, they would be facing a court-martial.

Williams and Carpenter both acknowledged that properly dealing with classified information like the specific details of military plans and operations can be burdensome, but the people in the group chat had all the support of the U.S. government behind them.

“They have the capacity with them to do this stuff correctly, and they chose not to, and that’s what I didn’t get,” Carpenter said.

Dan Grazier, a senior fellow for the National Security Reform Program at the nonprofit Stimson Center think tank in Washington, D.C., told Military.com on Tuesday that issues could have easily arisen had the initial strikes that were apparently being discussed in the chat gone wrong and involved civilian casualties or hit the wrong targets.

“Just from self-preservation, the administration would probably like to have a record that shows that, ‘No, we didn’t intend to strike that target … that was not part of the package … this is just an error,'” Grazier said.

Since the Signal chat isn’t part of a government system, its contents don’t automatically become government records.

“And if those records don’t exist, then they wouldn’t be able to prove that,” Grazier said.

Lawmakers from both parties with military and national security backgrounds agreed with the experts.

“This is all classified information,” Sen. Elissa Slotkin, D-Mich., a former CIA analyst and Defense Department civilian, posted on social media. “Even the fact that they were considering this strike is classified. And for good reason: The time and method of an attack, if intercepted by our enemies, could have gotten American troops killed.”

Rep. Don Bacon, R-Neb., a retired Air Force brigadier general, similarly said the officials on the Signal chat “were jeopardizing the aviators who were dropping these bombs.”

“There’s the old phrase from World War II: Loose lips sink ships,” Bacon told reporters Tuesday. “And so you’re doing it in an unclassified way where Russia and China could know about it two hours before the attack? It’s not right.”

While Waltz’s mistake in adding a reporter to the chat was understandable, Bacon added, Hegseth needs to take accountability for sharing classified information in an unclassified setting.

“It was the putting the classified information in there that was wrong,” said Bacon, who declined to say whether he believes Hegseth should resign. “The secretary did wrong there, and he should have known that.”

At a hearing before the Senate Intelligence Committee on Tuesday that was scheduled prior to the Atlantic story publishing, Gabbard and Ratcliffe both repeatedly and categorically denied that classified information was shared in the chat.

But toward the end of the hearing, they clarified that they meant there was no classified information that originated from the intelligence community they oversee and that they could not speak to whether any information originating from the Defense Department was classified since Hegseth is responsible for overseeing classification at the Pentagon.

Under questioning from Sen. Mark Kelly, D-Ariz., a former naval aviator, both Gabbard and Ratcliffe also said they could “not recall” specific details about the Signal thread, including whether weapons systems, timing and military units were mentioned.

Still, Gabbard acknowledged there was “discussion around targets in general.”

The Pentagon did not respond to a request for comment on the Atlantic report by Military.com’s deadline Tuesday, but Hegseth told reporters traveling with him in Hawaii on Monday that “nobody was texting war plans.”

In a sign of how serious the breach was, even some Republicans who have so far been deferential to the Trump administration have expressed concern.

Senate Armed Services Committee Chairman Sen. Roger Wicker, R-Miss., told reporters Tuesday that he and the committee’s top Democrat, Sen. Jack Reed of Rhode Island, conferred on the issue earlier in the day. While they didn’t settle on an exact next step, including whether to make Hegseth testify before the committee, Wicker said he and Reed will “look for some way forward” on a bipartisan committee response.

Still, other top Republicans are brushing off the issue as a harmless mistake.

“That mission was a success,” House Speaker Mike Johnson, R-La., told reporters Monday. “No one was jeopardized because of that. We’re grateful for that.”

Meanwhile, Democrats are hammering the administration, and some have already moved to demand answers without Republicans.

Reps. Adam Smith, D-Wash., the ranking member of the House Armed Services Committee; Gregory Meeks, D-N.Y., the ranking member of the House Foreign Affairs Committee; Jim Himes, D-Conn., the ranking member of the House Intelligence Committee; and Gerry Connelly, D-Va., the ranking member of the House Oversight Committee, sent a letter Monday to Hegseth, Rubio, Gabbard and Waltz with a slew of questions, including whether information in the chat “could have compromised the safety of members of the U.S. armed forces or those of a U.S. ally or partner.”

Sen. Tim Kaine, D-Va., also organized a separate letter to President Donald Trump demanding to know what disciplinary actions will be taken against those in the chat.

“It does not take much imagination to consider the likely ramifications if this information had been made public prior to the strike — or worse, if it had been shared with or visible to an adversary rather than a reporter who seems to have a better grasp of how to handle classified information than your national security adviser,” Kaine and 13 other Senate Democrats wrote in the letter. “This is an astonishingly cavalier approach to national security.”

However, the possibility of accountability seemed remote to some of the experts who spoke with Military.com.

“I don’t think there’ll be any direct political fallout, because this is not an administration that believes in accountability,” Williams said.

“There may be some poor, low-level staffer who gets fired, but I think that will be it. … I doubt there’ll be any sort of serious accountability.”

Related: The Last Houthi Attack Was Months Ago. But the US Military Has Now Launched an Open-Ended Campaign in Yemen.

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