No reason was provided for the abrupt exit of Phelan, the Navy’s top civilian official, whose departure comes at a time of heightened operational activity, including a blockade of Iranian ports and actions targeting vessels linked to Tehran during a fragile ceasefire in the ongoing regional conflict.

Pentagon spokesman Sean Parnell confirmed the move in a statement, while the administration named Hung Cao, the current undersecretary and a retired Navy captain, as acting secretary. Cao, a former combat officer and political candidate in Virginia, assumes the role immediately.

Phelan’s departure adds to a series of leadership changes under Defense Secretary Pete Hegseth, who has removed several senior military figures since taking office last year. Those include Randy George, the Army’s top uniformed officer, as well as earlier dismissals of Lisa Franchetti and Jim Slife.

Charles Q. Brown Jr. was also removed from his post as chairman of the Joint Chiefs of Staff.The timing of Phelan’s exit appeared sudden. He had addressed a major Navy conference in Washington a day earlier and held meetings with lawmakers, including members of the House Armed Services Committee, to discuss shipbuilding plans and budget priorities, according to official communications.

Phelan, a private investment executive and founder of Rugger Management LLC, had limited prior government or military leadership experience before his nomination in late 2024. His background included advisory work with Spirit of America, a nonprofit supporting defense-related initiatives in Ukraine and Taiwan.

His tenure coincided with an expanded U.S. naval presence globally. The Navy currently has multiple aircraft carriers deployed or en route to the Middle East, and U.S. forces remain positioned for potential renewed operations should the ceasefire with Iran collapse.

Separately, naval assets have supported counter-narcotics operations in the Caribbean and were involved in the January capture of Venezuelan leader Nicolás Maduro.Cao, who succeeds Phelan in an acting capacity, is a Vietnam-born refugee who later graduated from the U.S. Naval Academy and served in special operations units, including deployments in Iraq, Afghanistan and Somalia.

He previously ran unsuccessful campaigns for the U.S. Senate and House of Representatives in Virginia and has publicly criticized diversity and inclusion initiatives in the military, as well as COVID-19 vaccine mandates imposed on service members.

His appointment comes as the Trump administration continues to recalibrate defense leadership and policy priorities, including a broader rollback of diversity programs across the armed forces.