Defense secretaries usually take a hard line when it comes to the disclosure of classified information on their watch.

During the George W. Bush administration, Donald H. Rumsfeld said that those who break federal law in doing so should be imprisoned. His successor, Robert M. Gates, said it should be a career-ending offense for anyone in the Defense Department.

But after a leak on a commercial messaging app, the Trump administration has played down the episode and signaled there is little chance of an investigation.

President Trump has insisted that administration officials, including Defense Secretary Pete Hegseth, had committed only a minor transgression in discussing secret military plans in a group chat on Signal.

Discussing imminent combat operations on a platform not approved for classified information is, by itself, highly irregular. Even more extraordinary was the fact that a senior official had inadvertently invited a journalist to the chat.

Circling the wagons, the Trump administration has adopted the line that advance word of the timing and weapons platforms to be used in an attack were not classified, and Attorney General Pam Bondi signaled on Thursday that there was unlikely to be a criminal investigation.