Secretary of the US Navy John C. Phelan resigned on Wednesday effective immediately, the Pentagon announced.
“On behalf of the Secretary of War and Deputy Secretary of War, we are grateful to Secretary Phelan for his service to the Department and the United States Navy. We wish him well in his future endeavors," said Pentagon spokesperson Sean Parnell in a statement.
He added that Undersecretary Hung Cao will become Acting Secretary of the Navy.
The reason for Phelan’s resignation is unclear, but it comes just weeks after Secretary of War Pete Hegseth fired the US Army’s top officer, Gen. Randy George, as well as two other top generals in the Army.
Phelan had not served in the military or had a civilian leadership role in the service before President Donald Trump nominated him for secretary in late 2024.
The US Navy has played a key role in the war in Iran, imposing a naval blockade on the Strait of Hormuz.