On Thursday, the Pentagon's acting inspector general said that he will investigate Defence Secretary Pete Hegseth's use of the Signal messaging app to share plans for a military strike on Houthi militants in Yemen.

The investigation will also examine whether other defence officials used Signal, an encrypted app that is not approved for sharing classified information and is not connected to the Defence Department’s secure communication system. Hegseth's use of the app became known when journalist Jeffrey Goldberg from The Atlantic was accidentally added to a Signal group chat by national security adviser Mike Waltz. The chat included Hegseth, Vice President JD Vance, Secretary of State Marco Rubio, Director of National Intelligence Tulsi Gabbard, and others. They had come together to discuss military actions planned for March 15 against the Iran-backed Houthis.

The aim of this evaluation is to find out how well the Secretary of Defense and other Department of Defense (DoD) personnel followed DoD rules and procedures when using a commercial messaging app for official work. We will also check if they followed the rules for handling classified information and keeping records properly, said Acting Inspector General Steven Stebbins in a notification letter to Hegseth.

In the message chain, Hegseth shared the exact times when warplanes would take off and when the bombs would be dropped, before the pilots and crew carrying out the attacks for the United States were even in the air.

The review was started after a request from Senator Roger Wicker, a Republican from Mississippi and chairman of the Senate Armed Services Committee, along with Senator Jack Reed, a Democrat from Rhode Island and the top Democrat on the committee. During congressional hearings, Democratic lawmakers raised concerns about the use of the Signal messaging app and questioned military officers about whether it was appropriate to use such a commercial app for discussing military operations. Both current and former military officials believe that the information Hegseth shared on Signal was likely classified. However, the Trump administration has said that no classified information was actually shared.