Fox is the new acting deputy secretary of defense, the second-in-command at the Pentagon, after Ash Carter retired Monday afternoon.
Fox served as the budget director for defense, helping to prioritize spending and manage the sequester-tightened budget.
Before she moved to the Pentagon, Fox worked for the Center for Naval Analyses, developing tactics for aircraft carrier defense, similar to Kelly McGillis' character in Top Gun.
Except they didn't call Fox "Charlie." Her call sign was "Legs."