Defense Secretary Pete Hegseth on Friday fired Navy chief of staff Jon Harrison, delivering a blow to the insider who helped rewire internal protocols to fit the vision of the Trump administration’s defense agenda. 

Harrison’s removal comes after the confirmation of Navy Undersecretary Hung Cao, whom President Trump appointed to serve as the second-most senior civilian under Navy Secretary John Phelan.

Harrison and Phelan supported Hegseth in his ventures to introduce new military policies, cancel numerous outside contract agreements and reassign aides who were intended to help onboard Cao following his confirmation earlier this week.

“Jon Harrison will no longer serve as Chief of Staff to the Secretary of the Navy. We are grateful for his service to the Department,” a Department of Defense (DOD) official said in a statement to The Hill. 

Politico first reported Harrison’s ouster. Prior to his role as chief of staff, Harrison was appointed to the United States Arctic Research Commission by Trump in 2020.

While there, he served as chairman of the commission until the spring of 2021.

The Arctic region was flagged as a point of interest for White House officials early on in the second Trump administration, as the president floated the potential U.S. acquisition of Greenland and Vice President Vance visited the Danish territory in March to highlight its critical natural resources. 

The swipes at Greenland were ultimately followed by a June effort to restore the potential for oil and gas drilling on 13 million acres of government-owned Arctic land that had previously been restricted by the Biden administration.

A federal judge issued a Friday ruling stating the Biden administration went too far by indefinitely blocking new drilling off large portion of U.S. coast, in an order celebrated by major oil and gas groups.

Filip Timotija contributed to this article.