Chuck Hagel, the man Carter would replace if confirmed, as expected, by the Senate, has noted that when he took the job in February 2013, he had no idea that U.S. troops would be back in a fractured Iraq or that the deadly Ebola virus in West Africa would require an urgent deployment of the 101st Airborne Division. Even predictable challenges, such as pursuing and killing terrorists in the Middle East and Afghanistan, can be harder than they seemed on the outside, even for an experienced national security practitioner like the 60-year-old Carter. The Iraqi government wants to launch a major counteroffensive to regain lost territory, particularly the northern city of Mosul, but it is unclear whether Iraqi troops can succeed without U.S.