A senior advisor to Defense Secretary Pete Hegseth has departed the Pentagon following a tenure of six months, as confirmed by the Department of Defense (DoD) to Fox News Digital on Saturday.

Justin Fulcher told Fox News Digital he formally resigned on Thursday evening, describing the decision as entirely his own.

Fulcher noted that he initially intended to spend six months serving in government roles. Having fulfilled that commitment, he decided to leave on good terms. He highlighted the “remarkable efforts” being made by Hegseth “for the benefit of our military personnel and the nation.”

“The Department of Defense appreciates Justin Fulcher’s contributions on behalf of President [Donald] Trump and Secretary Hegseth. We extend our best wishes for his future prospects,” stated Sean Parnell, the chief Pentagon spokesperson, in a release.

In addition to advising Hegseth on personnel and policy, Fulcher played a role in several defense initiatives during his tenure, he told Fox News Digital.

Fulcher said he contributed to reviews of major acquisition programs aimed at strengthening lethality and the US industrial base, and helped streamline software procurement timelines “from years to months,” modernizing key IT systems across the department.

He also said he supported Hegseth in high-level meetings across the Indo-Pacific, including the Shangri-La Dialogue in Singapore, and participated in efforts that redirected nearly $50 billion from non-lethal line items into readiness and more impactful defense programs.

Fulcher praised the “dedicated men and women of the Department of Defense,” cited progress in “revitalizing the warrior ethos” and “rebuilding the military,” and thanked both Hegseth and Trump for their leadership. “Still, this is just the beginning,” Fulcher added.

Fulcher, who had served as a senior advisor to Hegseth since April, announced his departure Saturday afternoon in a message posted to X. 

“As planned, I’ve completed 6 months of service in government to my country,” he wrote, calling the experience “incredibly inspiring.”

“None of this could have happened without Secretary Hegseth’s decisive leadership or President Trump’s continued confidence in our team,” he wrote. “I will continue to champion American warfighters in all future endeavors.”

Fulcher joined the DoD earlier this year as part of Hegseth’s inner circle, a cohort of loyal advisers appointed after Hegseth took the helm at the Pentagon in Trump’s second term.

His departure comes amid a broader reshuffling of senior personnel inside Hegseth’s office.

At least six aides have left since January, though defense officials have downplayed the moves as standard transitions.

It’s unclear what Fulcher’s next step will be, though his statement suggests he intends to remain active in national security circles.

The Pentagon has not yet named a replacement.