On Thursday, President Obama named Gen. David Petraeus, the commander of U.S. forces in Afghanistan, the new CIA director, replacing Leon Panetta, who will succeed Robert Gates as secretary of defense.

Though the shakeup does not involve outside players, it promises to have an impact on America's foreign policy and war-fighting strategies as the country continues to be embroiled in three wars and the administration looks to make increased cuts to the Pentagon budget.

As Panetta and Petraeus prepare to take on their new roles, here's a look at some of the most notable defense secretaries and CIA directors in American history.