Defense Secretary Pete Hegseth’s tenure has seen a series of high-profile staff departures, leaving the Pentagon head without a chief of staff and other key advisers.

Hegseth’s inner circle saw another shake-up Saturday with the departure of senior adviser Justin Fulcher. Fulcher said in a statement to NewsNation that he had only planned to work six months in government.

The exit came three months after four top officials departed in quick succession amid infighting and an investigation into leaks. Hegseth’s chief of staff was moved elsewhere within the Pentagon days later.

Here are the top advisers to Hegseth who have left so far.

April 15

Dan Caldwell, one of Hegseth’s senior advisers, was escorted out of the Pentagon on April 15 and put on administrative leave amid a probe into information leaks at the department. 

Darin Selnick, the department’s deputy chief of staff, was suspended the same day, and Colin Carroll, the chief of staff to Deputy Defense Secretary Steve Feinberg, was also placed on leave the next day.

All three were fired April 18.

The leaks under investigation included a visit by Elon Musk to the Pentagon and military operational plans in Panama, Politico reported at the time.

The three ousted officials later said in a joint statement that they were “incredibly disappointed” in the way they had been forced out of the department.

“At this time, we still have not been told what exactly we were investigated for, if there is still an active investigation, or if there was even a real investigation of ‘leaks’ to begin with,” they wrote. They said they had been subject to “baseless attacks” by anonymous Pentagon officials.

April 17

Following the suspensions of Caldwell, Selnick and Carroll, John Ullyot, a press assistant to Hegseth, said April 17 that he had been asked to resign. 

Ullyot characterized the situation at the Pentagon as a “full-blown meltdown” in an opinion piece for Politico and contested claims that the three men had been ousted for leaking information.

“In the aftermath, Defense Department officials working for Hegseth tried to smear the aides anonymously to reporters, claiming they were fired for leaking sensitive information as part of an investigation ordered earlier this month,” he wrote.

Ullyot said at the time it was “hard to see” Hegseth remaining in his position long-term after repeated scandals.

The Atlantic reported Hegseth had shared secret plans to strike Houthi rebels in Yemen in a Signal chat that included the magazine’s editor in chief. Then, reports emerged Elon Musk had been invited to a top-secret Pentagon briefing on China, which was later canceled. Reports also circulated of Hegseth inviting his wife to sensitive briefings.

President Trump has continued to back Hegseth, saying in late April that he thought the defense secretary would “get it together.”

April 22

Hegseth said in an April 22 interview that Joe Kasper, his chief of staff, would move to a different role. News of the shift was first reported by Politico on April 18, the same day Caldwell, Selnick and Carroll were fired.

At the time, a senior U.S. defense official told The Hill that Kasper would stay at the Department of Defense as a special government employee, a position that lasts a maximum of 130 days. Kasper would handle “special projects,” the official said.

In March, Kasper had reportedly kick-started the probe into leaks of classified and sensitive information.

Politico reported April 22 that Kasper was seen as playing a key role in pushing out Caldwell, Selnick and Carroll. Kasper said in an interview with the outlet that he had been following Hegseth’s directive to investigate leaks.

July 15

Yinon Weiss, a DOGE team lead at the Pentagon, announced July 15 that he had left the role.

“Secretary Hegseth gave DOGE unprecedented opportunity and his front office made themselves available weekdays, evenings, and weekends; literally anytime we needed any guidance or support,” he wrote.

Weiss is a tech entrepreneur and former Marine.

The Washington Post reported Saturday that Hegseth had lashed out at Weiss in early April after Fulcher complained to the Pentagon chief. The nature of the dispute between Fulcher and Weiss was not clear, but Hegseth raised his voice at times, the newspaper reported.

July 19

Fulcher, who announced his departure from the Pentagon on Saturday, was appointed in late April as part of a wave of new aides. 

He was later promoted to senior advisor to Hegseth, and in April was named to a new Pentagon leadership team.

Fulcher had previously worked for the Department of Government Efficiency on defense matters. A March Forbes article raised questions about his business credentials, with one business partner claiming Fulcher owed him hundreds of thousands of dollars.

Fulcher said Saturday that he had completed six months of government work “as planned.”

The Washington Post reported Saturday that Fulcher’s desk had been relocated from outside Hegseth’s office to further down the hall. The Pentagon has cast his departure as amicable.

“The Department of Defense is grateful to Justin Fulcher for his work on behalf of President Trump and Secretary Hegseth. We wish him well in his future endeavors,” Pentagon spokesperson Sean Parnell told NewsNation, The Hill’s sister network.

Updated at 3:15 p.m. EDT