WASHINGTON (NewsNation) — A promotion for the general who was the last U.S. service member out of Afghanistan was put on hold by Sen. Markwayne Mullin, R-Okla., NewsNation sources confirm.

Lt. Gen. Christopher Donahue, who oversaw the U.S. withdrawal from Afghanistan in 2020 was nominated to lead the U.S. Army in Europe and Africa.

A source familiar with the confirmation process said it’s their understanding that Mullin held up the promotion, with his objection directly related to Donahue’s role in Afghanistan.

A NewsNation request for comment on Friday morning was not immediately returned.

The Senate Armed Services Committee approved nearly 1,000 promotions, including Donahue’s, earlier this week.

Who is Lt. Gen. Christopher Donahue?

A career special operations veteran, Donahue is known as the last U.S. service member out of Kabul, with his image captured in a hazy, night vision photo as he stepped on the last U.S. military aircraft out of Hamid Karzai International Airport on Aug. 30, 2021.

Donahue was in charge of the 82nd Airborne while it secured the airfield at the airport, an often chaotic scene as Americans and refugees raced to evacuate Afghanistan before an Aug 31, 2021, deadline to leave.

What is the promotion process?

Donahue, President Biden’s nominee to head the U.S. Army in Europe and up for promotion to four-star general, was one of nearly 1,000 military promotions the Senate Armed Services Committee approved on Tuesday.

Donahue’s name, however, was ​​not included in the promotions approved Thursday by the Senate before it left Washington, D.C., not to return until after the Thanksgiving Day holiday.

While his blocked military promotion is unusual, as officer promotions are typically uncontroversial and easily passed by the Senate, it’s not unheard of.

Sen. Tommy Tuberville, R-Ala., last year blocked several hundred general and flag officer promotions for months over his objection to the Pentagon’s policy of reimbursing those for travel costs when seeking an abortion out of the state in which they are based.

Though a hold can still be bypassed via a vote by the full Senate, it’s seen as unfavorable given that it can eat up floor time.

NewsNation affiliate The Hill contributed to this report.