“You make a movie with the secretary of defense you have,” Morris told me dryly, “not with the secretary of defense you want to have.”

Still, the filmmaker was smart to bookend the men, opposite ends of the same warmongering problem: McNamara was so droning and unemotive that he lulled listeners into thinking that nothing bad could be happening, while Rumsfeld was so energetic and blithe that it was hard to believe that people were dying and the war was being lost. Morris’s wife and collaborator, Julia Sheehan, said that McNamara was “The Flying Dutchman” wandering the earth looking for redemption, while Rumsfeld is the Cheshire cat.

“All we’re left with at the very end is this infernal grin,” Morris said. “Everybody wants this smoking gun. The entire Bush administration is a smoking gun.

“In his memos and homilies, Rumsfeld will say things that are just contradictory, as though by saying everything, you’ve covered all your bases,” Morris continued. “It’s deeply anti-rational, as if there’s no deep reflection or thought. You have no evidence? Well, ‘the absence of evidence is not evidence of absence,’ as Rumsfeld said about W.M.D. in Iraq. Taken to some crazy conclusion, you can justify anything that way.

“At times in his language, he descends into some strange insanity, as though he’s trying to convince himself.”