Carter's reputation stemmed from the long leash he was given under then-Defense Secretary Leon Panetta. Panetta, who retired in February, gave Carter near-unprecedented responsibility. But when Hagel arrived, the new secretary asserted himself quickly as the one in charge, redefining the roles and missions of the secretary and deputy secretary from what they had been to a more traditional dynamic.
As a result, the transition was not without its bumps, as FP previously reported. Early on, Hagel's office wasn't notified about an overseas trip on which Carter was about to embark. There were rumors of Hagel shutting Carter down in meetings. And Carter's own ego seemed to go unchecked. At a security conference in Aspen this summer, Carter spoke as if he were the one in charge, never once mentioning the secretary for whom he worked. In the hierarchy-heavy military culture, people started to take notice, and questions began to arise if the Hagel and Carter team would endure for long.
If his departure was inevitable, there was still a sense of loss, as Carter was well-liked for being the point man on a number of defense matters. The staff of Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, posted a statement on Facebook. "I've had the privilege of working with Deputy Secretary of Defense Ash Carter and am thankful for his contributions over the past four and a half years," Dempsey's statement said. "He's a tremendous leader and will always be a friend to our Armed Forces."
And Jeremy Bash, the former chief of staff under then-Secretary of Defense Leon Panetta, said Carter "grabbed the budget reins" for both Panetta and Hagel, "navigating budget cuts, sequestration, and shutdown planning in a way that few others could have done," Bash told FP. "He was handed a tough assignment, and he performed exceedingly well."
Bash, now managing director of Beacon Global Strategies, predicted Carter would return to government one day.
Washington's national security community immediately turned to the more vexing question of just who would succeed Carter.
Michèle Flournoy, the policy guru who resigned from the Pentagon's top policy job in February 2012 and was also on the shortlist to replace Panetta, is again high on the list. If not a shoo-in for the job, she will be seen as an extremely likely successor. Flournoy campaigned for Obama and is thought to be well-respected across Washington. Some Pentagon watchers believe that if Hillary Clinton wins the presidency in 2016, Flournoy will be an obvious choice as secretary. She might wait out Obama's second term for that possibility, passing on the Number Two job. Or, some believe, Flournoy, who has not had vast management experience on the Defense Department's scale, would be wise to jump at the chance to serve as deputy secretary. That would put her in line to succeed Hagel when the time comes.
"She's dialed in at the White House, she's respected on the Hill, had a good run as undersecretary for policy," said one former senior defense official of Flournoy. "The DepSecDef job is the final, developmental job to become SecDef, and she's young enough that she can hang around."
Frank Kendall, the undersecretary of defense for acquisition, technology, and logistics -- the building's top weapons buyer -- is also considered to be on the shortlist of possible successors. For now, Kendall is in the line of succession to become acting deputy secretary if Carter leaves without another deputy ready to step in.
As Pentagon watchers float other names, two relative unknowns have emerged: BAE Systems' Linda Hudson and the CIA's general counsel, Stephen Preston.
Carter's departure from the Pentagon won't be the last high-profile defection. Pentagon policy chief Jim Miller, long-rumored to be leaving, is expected to hand in his own resignation in the coming weeks, with a departure by the end of the year very likely, multiple sources say.
For now, the Pentagon will prepare to fill Carter's bureaucratic shoes, ones that even Hagel acknowledges will be rather big ones to fill.