Defense Secretary Chuck Hagel announced Tuesday that Christine Fox, former director of Cost Assessment and Program Evaluation, would serve as the acting deputy secretary of defense until a permanent successor for Ashton Carter can be found.

Hagel said he recommended her to President Barack Obama, who made the official appointment, because she is “a brilliant defense thinker and proven manager.”

Christine Fox. Photo: Defense Department

“As a key leader of the Strategic Choices and Management Review, she helped identify the challenges, choices, and opportunities for reform facing the department during this period of unprecedented budget uncertainty,” Hagel said in a statement. “She will be able to help me shape our priorities from day one because she knows the intricacies of the department’s budget, programs and global operations better than anyone.

Fox will start the new job on Thursday and, under federal law, can serve up to 210 days without Obama nominating someone as the permanent deputy secretary. After a nomination is made, she could serve as acting deputy secretary for as long as it takes for the appointee’s nomination to go through the Senate confirmation process.

In the next 210 days, the Defense Department will face the results of the budget conference committee, be it another continuing resolution, a repeal of sequestration or any number of other scenarios; it will submit its fiscal year 2015 budget request even though the department still lacks an FY ’14 budget; it will submit its Quadrennial Defense Review to Congress to outline its priorities and strategies for the next four years; and it will determine what presence, if any, the military will have in Afghanistan after 2014.

With so many pivotal decisions to be made in the coming months, Fox’s 30-plus years of service in defense analysis will go a long way in advising Hagel and DoD. Fox spent four years as CAPE director before leaving over the summer to serve as a principle technical adviser for the Johns Hopkins University Applied Physics Lab’s National Security Analysis Team. She also previously served as the president of the Center for Naval Analyses (CNA), among other positions at CNA.

On Sept. 30, she spoke frankly at a panel event hosted by the Center for a New American Security, entitled “Maintaining a Strong Defense-Industrial Workforce,” to describe the challenges DoD faces in this budget environment. She argued the department could trim spending if it were given the chance to do it smartly, but she said in the short-term sequestration is doing great harm to both the military and its industrial base.

Fox said at the event that even if Congress granted DoD flexibility in cutting about $50 billion from its budget every year for the next nine years–which some lawmakers have suggested would be the best-case scenario, given a lack of common ground in agreeing on alternatives to across-the-board budget cuts–DoD still couldn’t generate that much in savings without making harmful decisions.

“Flexibility alone is not the solution to the sequestration impact on our industry and workforce,” she said. Rather, “the biggest thing that would help us is to backload the reductions. Let us do it strategically and put in place the things it would take to get the levels down so the budget is reduced in the out-years, but give us the time to get there. That would not force us to do these nonstrategic things.”