The Defense Department inspector general's office said Thursday it will review Defense Secretary Pete Hegseth's use of commercial messaging apps like Signal to discuss sensitive details on planned U.S. airstrikes in Yemen.
The IG's evaluation comes a little over a week after The Atlantic reported that members of President Donald Trump's Cabinet -- 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 Signal where they discussed upcoming strikes against Yemen's Houthi rebels.
The magazine became aware of the discussion after Waltz added its editor-in-chief, Jeffrey Goldberg, to the chat. The revelations that top national security officials in the Trump administration were using the commercial app and not secure communications triggered widespread public criticism and concerns that intercepted messages could have endangered U.S. troops carrying out the strikes.
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The inspector general's office said it will look into "recent public reporting on the secretary of defense's use of an unclassified, commercially available messaging application to discuss information pertaining to military actions in Yemen in March 2025," the memo announcing the investigation said.
The evaluation began after the IG received a bipartisan letter from the Senate Armed Services Committee chairman, Sen. Roger Wicker, R.-Miss., and Sen. Jack Reed, D-R.I., the ranking member.
"The objective of this evaluation is to determine the extent to which the secretary of defense and other DoD personnel complied with DoD policies and procedures for the use of a commercial messaging application for official business," the memo said. The IG will also "review compliance with classification and records retention requirements."
NPR reported that the Pentagon had warned its employees in the days after this incident that Signal was not safe to use even for discussing unclassified information.
In defending themselves from criticism following the news, officials like Hegseth and Waltz have argued that the information they described in the group chat was unclassified.
However, days later, The Atlantic revealed that Hegseth was posting specific times that Navy jets would be taking off and approaching their targets, as well as when Tomahawk missiles would be launched.
Experts told Military.com that operational details like that are almost always classified and that sharing this type of 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 last week.
Carpenter and rank-and-file troops remarked that, if a service member were to do something similar to what Hegseth was caught doing, they would likely face a court-martial.
Military.com has asked the office of the chairman of the Joint Chiefs of Staff whether the acting chairman, Adm. Christopher Grady, or his staff use Signal to discuss national security matters but, after more than a week, they have not provided an answer.
The IG's memo noted that investigators "may revise the objective as the evaluation proceeds."
Mollie Halpern, a spokeswoman for the inspector general's office, told Military.com on Thursday that the resulting report will be "nonpartisan, and it will be thorough."
"And whatever the results of this evaluation are, we will release the unclassified report," she said.
The report will be a very public test of the ability of the inspector general to remain independent of political pressure, given that Trump fired the Senate-confirmed head of the watchdog, along with about 17 other inspectors general shortly after he was inaugurated in January.
The firings violated a 2022 law that requires that Congress be notified in advance of any removal of an inspector general, but lawmakers have not taken action to enforce the law.
The Defense Department's IG office is currently being headed up by Steven Stebbins, who was the principal deputy inspector general until stepping up into the acting IG position.
Democrats on Thursday took the move as a small victory, and Reed, the ranking member of the Senate Armed Services Committee who called for the investigation, said he not only welcomed the investigation but that he has "grave concerns about Secretary Hegseth's ability to maintain the trust and confidence of U.S. service members and the commander in chief."
Sen. Chris Coons, D-Del., also said that he was glad that the inspector general is looking into the matter but noted in a post to social media Thursday that "it's clear this administration's use of Signal to discuss sensitive information goes far beyond [the Defense Department]."
Politico reported on Wednesday that Waltz and his team set up at least 20 different Signal group chats for various crises around the world that the National Security Council was dealing with.
