'The Unknown Known' Trailer: Errol Morris Takes On a Cagey Donald Rumsfeld

The clip shows just how hard it is to corner Bush's former Pentagon chief but also raises the question of why Rumsfeld agreed to do the doc in the first place.

The new trailer for legendary documentarian Errol Morris' (Thin Blue Line, Gates of Heaven) film about Donald Rumsfeld hit the web this weekend. It begins with Morris asking the former defense secretary to read from one of his infamous memos. Rumsfeld recites, "All generalizations are false, including this one," then looks at Morris with a Cheshire cat grin and says, "There it is." This moment, along with many others in the trailer, make one thing abundantly clear: Those hoping for a Fog of War-like confession or sense of humility from Rumsfeld, similar to what Morris extracted from Vietnam architect Robert McNamara, will be disappointed.

The trailer also shows that the film is not simply focused on Rumsfeld's role in shaping our post-9/11 military response, but is to some degree a biography as well. Highlighted in the trailer are the different paths the ambitious Rumsfeld's career could have taken, including if President Ronald Reagan had chosen him to be his running mate in 1980 and the very real prospect that he might have become president himself.

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From a marketing and publicity angle, one of the interesting aspects of the trailer is that blurbed reviews come from political commentators, in addition to more traditional film reviews. Morris' own political point of view isn't hidden. Set against a devastating montage of images of the Pentagon burning on 9/11, Abu Ghraib, Guantanamo Bay and the bombing of Iraq, Rumsfeld narrates: "Free people are free to make mistakes and commit crimes and do bad things. … You have to pick and choose, and to the extent that you pick and choose and are wrong, the penalty can be enormous."

This leads to what might be the biggest "unknown knowns" of this film: Why in the world did Rumsfeld agree to participate?

The film is set to be released on April 4.