The two longest-serving US secretaries of defense are Robert McNamara and Donald Rumsfeld. McNamara spent 10 more days running the Pentagon than Rumsfeld did. He also served uninterruptedly. Rumsfeld held the post under presidents Ford and George W. Bush. Both men are associated with disastrous wars, making them likely the two most controversial secretaries of defense. Certainly they’re the only two to be subjects of Errol Morris documentaries.
“The Fog of War” (2003), about McNamara, won Morris a best documentary feature Oscar. “The Unknown Known” takes its title from a favorite phrase of Rumsfeld. It also accurately describes its subject, whose smiling inscrutability makes him consistently fascinating and often maddening.