A Republican senator has blocked the promotion of U.S. Army Lt. Gen. Christopher Donahue, who commanded the military’s 82nd Airborne Division during the U.S. withdrawal from Afghanistan and was the last American soldier to leave the country in 2021.

An official, speaking on condition of anonymity, said the hold had been placed by Sen. Markwayne Mullin, who did not respond to a request for comment on why he blocked the promotion.