USA TODAY

Army Secretary Dan Driscoll submitted his resignation to President Donald Trump on Aug. 31, the White House said, departing after repeated tensions with Pentagon chief Pete Hegseth.

Driscoll's resignation, which comes 18 months after he assumed the post, leaves the Army without a Senate-confirmed leader. Gen. Christopher LaNeve has served as the Army's acting chief of staff after Hegseth asked Gen. Randy George to step down from his position in April and immediately retire.

Driscoll is the latest military leader to leave his office amid a string of departures. Gen. Christopher Donahue, the Army's commander in Europe and Africa, left his post in June after Hegseth downgraded his command. Hegseth also fired Navy Secretary John Phelan in April.

Reuters, CNN and multiple other outlets reported that Driscoll has repeatedly expressed concerns about readiness in the Army and the removal of top Army officials, such as George.

Driscoll and George grew close as they collaborated on efforts to modernize the Army, pushing for the adoption of additional technology as the war in Ukraine has ushered in a new era of drone warfare. In remarks to lawmakers shortly after George's ouster, Driscoll heaped praise on his former colleague.

"There is no person that has more respect for Gen. George," Driscoll said during a House Appropriations Defense Subcommittee hearing in April. "He was an amazing transformational leader."

George established a new assault battalion in Europe to study drone and robotic warfare, but his successor, LaNeve, killed the initiative, according to reporting from the Wall Street Journal and CBS News.

White House spokeswoman Anna Kelly said in a statement that "Secretary Driscoll has been highly effective in advancing President Trump's agenda to Make America Strong Again at the Department of the Army by providing outstanding leadership during historic military operations, restoring an emphasis on readiness and lethality, assisting with negotiations between Russia and Ukraine, and more."

"The United States Army is more powerful than ever thanks to his work alongside the Commander-in-Chief and Secretary of War," Kelly added.

The Wall Street Journal, which first reported on Driscoll's resignation, also reported that Dave Fitzgerald, the deputy undersecretary of the Army, is expected to resign later this week. The Pentagon referred questions to the Army.

Driscoll is a former adviser to Vice President JD Vance. The two men became close after they were classmates at Yale Law School.

_White House Correspondent Joey Garrison contributed reporting to this story._