Errol Morris recalls that when he first met Donald H. Rumsfeld, he asked that former defense secretary for President George W. Bush what he thought of "The Fog of War," Mr. Morris's 2003 Oscar-winning documentary about Robert S. McNamara, another towering Pentagon chief toppled by a misguided war.
Mr. Rumsfeld said that he disliked it because McNamara, who spent much of the film regretting past mistakes, had nothing to apologize for.
In short, a film about this man wasn't likely to reveal any deep, dark secrets. Instead, Mr. Morris decided to focus on the memos that Mr. Rumsfeld wrote — "snowflakes," they were called, because he blanketed his staff with thousands of them, like blizzards of white paper — as a Rosetta stone to his subject's character.
The resulting film, "The Unknown Known," which opens on Friday, is structured much like "The Fog of War." For 96 minutes (cut down from 34 hours of conversation), Mr. Rumsfeld looks into the camera, answering, or finessing, questions about Iraq, his work for several presidents, the nature of truth and more.