WASHINGTON — Navy Secretary John Phelan is stepping down “effective immediately,” the Defense Department said, the latest high-profile Pentagon departure amid the war in Iran.

Pentagon spokesman Sean Parnell, who announced the decision in a post on X, gave no explanation, and it wasn’t immediately clear if Phelan had been fired or was resigning on his own. Phelan’s abrupt departure comes as the Navy is helping oversee a blockade of the Strait of Hormuz, one of its biggest operations in decades.

Phelan is only the latest high-level departure from the Pentagon since the Iran war began. Earlier this month, Defense Secretary Pete Hegseth asked Army Chief of Staff General Randy George to step down.

President Donald Trump nominated Phelan, a campaign donor and businessman, before his second inauguration. Phelan was also helping oversee a major modernization drive among U.S. shipbuilders as the administration seeks tens of billions of dollars in new funding to expand the Navy.

“We wish him well in his future endeavors,” Parnell said. Undersecretary Hung Cao becomes acting secretary.

Asked for comment, the White House referred reporters to Parnell’s X post.

Phelan co-founded MSD Capital more than two decades ago to manage the family fortune of computer maker Michael Dell. Phelan later founded Rugger Management, a private investment firm based in Palm Beach, Florida.

Born in South Vietnam, Cao came to the U.S. in 1975 after the fall of the country, and graduated from the Naval Academy. After leaving the military, he became a vice president at CACI International, an information technology company and government contractor. He ran an unsuccessful campaign for U.S. Senate in Virginia in 2024.

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(With assistance from John Harney and Jennifer A. Dlouhy.)

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