WASHINGTON (AP) — Navy Secretary John Phelan is leaving his job, the Pentagon abruptly announced Wednesday, the first head of a military service to depart during President Donald Trump’s second term but just the latest top defense leader to step down or be ousted.

No reason was given for the unexpected departure of the Navy’s top civilian official, coming as the sea service has imposed a blockade of Iranian ports and is targeting ships linked to Tehran around the world during a tenuous ceasefire in the war. Another Trump loyalist is taking over as acting head of the Navy: Undersecretary Hung Cao, a 25-year Navy combat veteran who ran unsuccessful campaigns for the U.S. Senate and House in Virginia.

Phelan’s departure is the latest in a series of shakeups of top leadership at the Pentagon, coming just weeks after Defense Secretary Pete Hegseth fired the Army’s top uniformed officer, Gen. Randy George. Hegseth also has fired several other top generals, admirals and defense leaders since taking office last year.

The firings began in February 2025, when Hegseth removed military leaders, including Adm. Lisa Franchetti, the Navy’s top uniformed officer, and Gen. Jim Slife, the No. 2 leader at the Air Force. Trump also fired Gen. Charles “CQ” Brown Jr. as chairman of the Joint Chiefs of Staff.