In a move that rattled an already beleaguered Defense Department, the Pentagon announced Thursday that Deputy Secretary Ashton Carter would step down from his post in December.
"The Department will miss him, I will miss him," Defense Secretary Chuck Hagel said in announcing that Carter was resigning and would leave the Pentagon on Dec. 4 after more than four years at the Pentagon under Hagel and former Defense Secretaries Robert Gates and Leon Panetta.
Hagel said he had met with Carter, who oversaw the introduction of mine-resistant vehicles to the military and struggled to rein in ballooning costs on the F35 Joint Strike Fighter program, earlier Thursday and "reluctantly accepted his decision to step down."
Hagel called Carter, who earlier worked on defense matters in the administration of former President Bill Clinton, "a brilliant strategist and an excellent manager who helped enhance the Department's buying power."
Carter "will be especially remembered for his tremendous efforts to provide more agile and effective support for our warfighters," a reference to Carter's oversight of the program that sped thousands of Mine Resistant Ambush Protected vehicles (MRAPs) to Iraq and Afghanistan.
The resignation of the 59-year-old Carter, while DoD struggles with the government shutdown and the escalating demands for budget and personnel cuts under the sequester process, stunned many in the Pentagon, in defense industry circles, and in the community of defense consultants and analysts.
"This comes as a shock to many people in the business," said Loren Thompson, director of the Lexington Institute and a Pentagon consultant. "We expected that eventually he would be Secretary of Defense."
Thompson speculated that Carter may have grown weary of the 12-15 hour days and the constant second-guessing from a gridlocked Congress on strategy and budgets.
"I'm very surprised and sorry that he's not going to be secretary of Defense because he would've been the best," Thompson said of Carter.
Carter, who has an undergraduate degree from Yale and a doctorate in theoretical physics from the University of Oxford, was believed to be on President Obama's short list for Secretary of Defense when Panetta resigned earlier this year, only to see the job go to Hagel.
However, Pentagon officials moved quickly to stress that Carter's departure was not the result of any rift or friction between Carter and Hagel.
"The decision to depart the Pentagon later this year was Deputy Secretary Carter's and his alone," George Little, the Pentagon Press Secretary, said in a statement. "He'll be missed by the Secretary. They've had a strong and effective working relationship and friendship that will continue for the next two months and beyond."