The Pentagon's acting inspector general announced on Thursday that an investigation would be conducted into Defense Secretary Pete Hegseth's use of the Signal messaging app to discuss plans for a military strike targeting Houthi rebels in Yemen.
The review will also look at other defense officials' use of the publicly available encrypted app, which is not able to handle classified material and is not part of the Defense Department's secure communications network.
Hegseth's use of the app came to light when a journalist, Jeffrey Goldberg of The Atlantic, was inadvertently added to a Signal text chain by national security adviser Mike Waltz.
The chain included Hegseth, Vice President JD Vance, Secretary of State Marco Rubio, Director of National Intelligence Tulsi Gabbard and others, brought together to discuss March 15 military operations against the Iran-backed Houthis.
"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 acting inspector general, Steven Stebbins, said in a notification letter to Hegseth.
The letter also said his office "will review compliance with classification and records retention requirements."
Hegseth and other members of the Trump administration are required by law to archive their official conversations, and it is not clear if copies of the discussions were forwarded to an official email so they could be permanently captured for federal records keeping.
The Pentagon referred all questions to the inspector general’s office, citing the ongoing investigation.
In the chain, Hegseth provided the exact timings of warplane launches and when bombs would drop – before the men and women carrying out those attacks on behalf of the United States were airborne.
The review was launched at the request of Sen. Roger Wicker, R-Miss., chairman of the Senate Armed Services Committee, and Rhode Island Sen. Jack Reed, the committee’s top Democrat.
In congressional hearings, Democratic lawmakers have expressed concern about the use of Signal and pressed military officers on whether they would find it appropriate to use the commercial app to discuss military operations.
Both current and former military officials have said the level of detail Hegseth shared on Signal most likely would have been classified. The Trump administration has insisted no classified information was shared.
Waltz is fighting back against calls for his ouster and, so far, President Donald Trump has said he stands by his national security adviser.
On Thursday, Trump fired several members of Waltz's staff after far-right activist Laura Loomer urged the president to purge staffers she deemed insufficiently loyal to his "Make America Great Again" agenda, several people familiar with the matter said.
In his Senate confirmation hearing Tuesday, Trump's nominee for chairman of the Joint Chiefs of Staff, Lt. Gen. Dan Caine, would not say whether the officials should have used a more secure communications system to discuss the attack plans.
"What I will say is we should always preserve the element of surprise," Caine told senators.
