By Carlo Muñoz - 12/03/13 12:04 PM EST
Top Pentagon official Christine Fox will replace outgoing Deputy Defense Secretary Ashton Carter, Defense Secretary Chuck Hagel announced Tuesday.
Fox, who led the department's cost assessment and program evaluation shop, will take the reins as the Pentagon's No. 2 leader on Thursday, Hagel said.
Hagel called Fox a "brilliant thinker and proven manager," and noted she played a key planning role in department's new strategy to deal with the massive, across-the-board budget cuts under the White House's sequestration plan.
Released in July, the plan considers shrinking the Army from 490,00 to between 380,000 and 450,000 troops to deal with the $500 billion in mandatory spending cuts.
The cuts began in March and would reduce Pentagon spending by $52 billion next year.
"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 Tuesday.
Fox will be able to help recalibrate the department's priorities, in light of sequestration, "from day one because she knows the intricacies of the department's budget, programs and global operations better than anyone," Hagel added.
Carter's departure from the Pentagon ends his four-plus-year stint as the department's second-in-command.
Along with Carter, former Pentagon policy chief Jim Miller, head of special operations and low-intensity conflicts at the Pentagon Michael Sheehan, DOD's Deputy Chief Management Officer Beth McGrath and Pentagon Press Secretary George Little have all left or announced plans to leave the Pentagon.