GEOFF BENNETT: Now to new revelations involving Defense Secretary Pete Hegseth.

The Washington Post first reported and the "News Hour" can confirm that Hegseth had the unclassified messaging app Signal installed on a computer in his Pentagon office.

That's after reporting that Hegseth shared highly sensitive and detailed attack plans in a Signal group chat last month that included his wife, brother and lawyer, in addition to top national security officials, hours before a mission was launched against Houthi forces in Yemen.

All of this is unfolding as chaos is mounting at the Pentagon with the firings of top Hegseth aides.

We're joined now by Dan Lamothe, who covers the U.S. military and Pentagon for The Washington Post.

Dan, it's great to have you here.

So why the special computer setup?

Why is Secretary Hegseth finding new ways to use this commercial messaging app Signal on his Pentagon computer?

DAN LAMOTHE, The Washington Post: This speaks to the need and desire that he and other Pentagon officials saw for this platform in an environment where you simply are not allowed to have your cell phone.

All of these are known as SCIFs.

It's basically a compartmented part of the building where you're not allowed to have personal electronics.

So to get around that, they installed a special line, a separate computer and basically had a way for him to message from the computer while still in a classified environment with classified systems right nearby.

GEOFF BENNETT: So the fact that this app is not part of the secure information-sharing architecture within the Pentagon, I mean, is that an operational breach?

DAN LAMOTHE: Wouldn't be an operational breach necessarily to just have it, but how you use it matters a great deal here.

He's obviously under scrutiny for posting details about a operation before it occurred in at least two different Signal chats.

Those details, what kind of aircraft, what time strikes might occur, what kind of weapons, those are always classified prior to some sort of attack or strike or operation occurring.

So you end up in a situation where there's a lot of people, including retired four-star generals and admirals, who are increasingly vocal about basically the video and the audio not matching there.

The idea that he can say none of this was classified doesn't ring true to that.

GEOFF BENNETT: Meantime, there are also reports of a crisis of leadership, a leadership vacuum at the Pentagon, apparent infighting that led to surprise firings.

Pete Hegseth has the least experience of any defense chief.

And, at the moment, as we sit here and speak, he has no chief of staff, no deputy chief of staff or senior adviser.

How is that affecting the day-to-day operations and morale at the Pentagon?

DAN LAMOTHE: Morale is low at this point.

There's frustration and exhaustion with a lot of employees.

And there's a sense of confusion and concern that we haven't hit rock bottom.

We had three individuals fired last week, Darin Selnick, Dan Caldwell, and Colin Carroll.

They were all senior officials.

All had senior advisory roles.

Caldwell and Selnick actually knew Hegseth and went back with him years.

These are not people you would have expected to be in such conflict with him and his staff.

And then the chief of staff, Joe Kasper, his last day is actually basically today.

And there's no clarity on who that chief of staff is going to be going forward.

GEOFF BENNETT: NPR reported this week that the White House is actively looking for Hegseth's replacement.

White House officials, President Trump, have pushed back on that.

Based on your reporting, is Secretary Hegseth on solid ground right now?

DAN LAMOTHE: I think he is at the moment.

We have been hearing the president is increasingly concerned.

The president is increasingly paying attention.

I had one official who's familiar with the president's thinking who said: "Well, sure, he's got his support now.

That's usually what he says.

And then one day you randomly wake up and see the post on social media saying that basically thank you for your service."

We're wondering.

There is increasingly concern in the building whether or not we're heading in that direction now.

But there's no clarity on who might replace him or on what timeline or whether or not he can just kind of ride this out.

GEOFF BENNETT: Dan Lamothe of The Washington Post, thank you for joining us with your insights this evening.

We appreciate it.

DAN LAMOTHE: Thank you.