The three-star general who has been serving as the senior military assistant to Defense Secretary Ash Carter was abruptly fired Thursday amid allegations of misconduct.
Army Lt. Gen. Ron Lewis was removed from his post Thursday morning after Carter learned of the allegations Tuesday night, a senior defense official said.
"The secretary was very surprised to learn of these allegations," the official said.
Pentagon officials declined to reveal details of the alleged misconduct.
Carter has referred the matter to the Defense Department's inspector general for an official investigation.
For now, Lewis will report to the Army Vice Chief of Staff Gen. Daniel B. Allyn.
Other top generals facing IG investigations have been permitted to remain in their jobs.
For example, Marine Corps Gen. James Cartwright was the vice chairman of the Joint Staff in 2011 while the IG investigated allegations that he had an improper relationship with a female subordinate.
Navy Adm. James Stavridis remained in his post as commander of U.S. European Command in 2012 while the IG investigated allegations that he misused government travel privileges and improperly accented gifts.
In both cases, the IG identified minor infractrions that resulted in no disciplinary action.
Lewis, a Chicago native and former attack helicopter pilot, deployed to Afghanistan in 2008 as commander of an aviation brigade attached to the 101st Airborne Division. In 2013, he served in Afghanistan as the division's deputy commanding general. He later served as the chief of Army public affairs.
Lewis' desk was adjacent to Carter's office in the Pentagon's E-ring, and the general routinely accompanied Carter on his trips abroad. As senior military assistant, Lewis' job was to advise the Pentagon's top civilian leader on a range of issues related to policy, strategy and budgets.
Carter’s selection of Lewis was one of the first personnel moves the new secretary made when he assumed office.
The two men have a long history. Lewis twice previously filled the role of military adviser to Carter, first when Carter was the undersecretary of defense for acquisition, technology and logistics in 2011, and then assuming the same role when Carter took over as deputy secretary of defense until Lewis redeployed to Afghanistan in early 2012.
Given that connection, Pentagon watchers had identified Lewis as a rising star inside the Pentagon.
Earlier this summer, Andrew Hunter of the Center for Strategic and International Studies, who served under Carter during his tenure as undersecretary of acquisition, technology and logistics, praised Lewis as the type of leader that Carter worked well with.
"It probably wouldn't be a stretch to suggest Ron Lewis is destined for great things," Hunter said in a June interview. "I think he's someone who has that combination of brainpower and ability to do very complex operational jobs."
Carter himself praised Lewis in an Oct. 14 speech at the Association of the U.S. Army annual meeting.
"It’s my privilege, also, to work closely with some of the terrific soldiers, and I want to take a moment to recognize some of them who are right around me every day, starting with my senior military assistant, Lt. Gen. Ron Lewis," Carter said. "Time after time, whenever I’ve needed Ron’s counsel and vision, I’ve been able to count on him. Thanks, my friend."
Defense News reporter Aaron Mehta contribued to this story