Patrick Shanahan

It's a difficult time for the Pentagon to be without a permanent U.S. defense secretary.

President Donald Trump said via Twitter on Tuesday that Army Secretary Mark Esper will take over as acting Pentagon chief.

Army Secretary Mark Esper will become acting SecDef, President Donald Trump tweeted.

The Pentagon announced it has concluded its reviews of a 2017 ambush that left four U.S. soldiers dead in Niger.

South Korea and the U.S. last year eliminated larger military drills and said they would replace them with smaller exercises.

A defense official said Shanahan is considering a clearer directive to the military about avoiding political situations.

Shanahan said he can't ignore the communist giant's military development on the manmade outposts.

Acting Defense Secretary Patrick Shanahan arrived Wednesday in Asia on a high-profile weeklong trip.

Two key House lawmakers slammed a Pentagon proposal that would limit what top brass tells Congress about operational plans.

Acting Defense Secretary Shanahan defended the Pentagon's move to carry out a joint show of force in the Persian Gulf.