The move is the latest major shakeup at the Pentagon under President Donald Trump's administration, which has already fired a number of senior officers this year.

The memo also calls for an additional 10 percent reduction in the number of general and flag officers, and a 20 percent cut in the number of general officers in the National Guard.

It did not specify how the reductions would be accomplished.

There were 38 four-star officers -- the highest rank that can usually be achieved in the US military -- and a total of 817 generals and admirals in the active-duty forces as of March 2025.

The cuts are aimed at removing "redundant force structure to optimize and streamline leadership by reducing excess general and flag officer positions," the memo said.

"Through these measures, we will uphold our position as the most lethal fighting force in the world, achieving peace through strength and ensuring greater efficiency, innovation, and preparedness for any challenge that lies ahead," it added.

Since beginning his second term in January, Trump has overseen a purge of top officers, including chairman of the Joint Chiefs of Staff general Charles "CQ" Brown, whom he fired without explanation in February.

Other senior officers dismissed this year include the heads of the Navy and Coast Guard, the general who headed the National Security Agency, the vice chief of staff of the Air Force, a Navy admiral assigned to NATO, and three top military lawyers.

Hegseth has insisted the president is simply choosing the leaders he wants, but Democratic lawmakers have raised concerns about the potential politicization of the traditionally neutral US military.