Lt. Gen. John Allen, the White House's choice to lead the war effort in Afghanistan, is best known for his leadership in helping pacify what was once Iraq's most volatile province.
Serving in Iraq from 2006 to 2008, then Brig Gen. Allen, the deputy commander in Anbar province, helped coax Sunni tribal leaders to turn against Al Qaeda affiliated militants and align with the U.S.
The so-called Sunni Awakening was first nurtured by an Army colonel, but Gen. Allen quickly backed then-Col. Sean MacFarland's efforts and worked to spread the effort around the province.
Like Gen. David Petraeus, Gen. Allen, 57 years old, is known for his skills at negotiating with local leaders. Gen. Allen spent months coaxing Sunni tribesmen to switch sides in Anbar, and back the American effort.
As commander in Afghanistan, Gen. Allen will be the first Marine to hold the top post in either that war or Iraq.
Marines have long been the experts at so-called small wars, and some defense officials say Gen. Allen will bring a different touch to the conflict in Afghanistan.
Still, Andrew Exum, fellow with the Center for a New American Security, said Gen. Allen will likely continue Gen. Petraeus' approach. "I do not get the sense that anyone, at this phase in the war and looking forward to the upcoming transition, is looking for radically new perspectives on the conflict on Afghanistan but rather someone who will execute the transition already envisioned by the White House," Mr. Exum said.
Gen. Allen is close to Gen. Petraeus, and like the outgoing commander, understands the top job is as much about good communication and diplomacy as it is combat experience, officials said.
"He is very savvy, in terms of policy and politics," said a U.S. official. "You have a guy who understands this is a perceptions war, a hearts and minds war, and a diplomatic war. He is open-minded."
Although some in the military have said Gen. Allen lacks senior level combat command, he was the White House's top pick for the role, largely because of his experience as the deputy at Central Command.
In Tom Ricks's book, "The Gamble," Gen. Allen was quoted as saying that if he hadn't become a Marine officer he would have been an archeologist. Gen. Allen said he had admired the work of Gertrude Bell, the British writer and archeologist who was partly responsible for the creation of modern Iraq in the 1920s.
"She had the life I perhaps would have liked to have had," Gen. Allen told Mr. Ricks.
—Adam Entous contributed to this article.