In the spring, defence secretary Pete Hegseth decided not to promote a senior army officer who had led troops over five tours in Afghanistan and Iraq because Hegseth suspected, without evidence, that the officer had leaked sensitive information to the news media, according to three people with knowledge of the matter.

When Lt. Gen. Douglas A. Sims II was cleared of the allegations, Hegseth briefly agreed to promote him, only to change course again early this month, the officials said. This time, Hegseth maintained that the senior officer was too close to Gen. Mark Milley, a former chairman of the Joint Chiefs of Staff whom President Donald Trump has accused of disloyalty.

Hegseth’s sudden reversal prompted a rare intervention from Gen. Dan Caine, the current chairman of the Joint Chiefs. He urged Hegseth to reconsider, said the officials, who spoke on the condition of anonymity to discuss internal deliberations.

Hegseth met General Sims one final time but refused to budge. General Sims is expected to retire in the coming months after 34 years in the military, officials said. Through a spokesman, General Sims and General Caine declined to comment. A Pentagon spokesman declined to comment on Hegseth’s role.

The standoff over his promotion reflects an ongoing clash between Hegseth’s highly partisan worldview, in which he has written that the Democratic Party “really does hate America”, and the longstanding tradition of an apolitical military that pledges an oath to the Constitution.

New York Times News Service