The Unknown Known

Towards the end of Errol Morris's conversations with Donald Rumsfeld, the documentarian – frustrated by a volley of evasions – asks the left's favourite bellicose bogeyman why he ever agreed to the interview. "That is a vicious question," Rumsfeld replies with a characteristic vulpine grin. He then proceeds to not answer it.

Any consideration of Morris's latest film invites constant cross-references to the same director's more gripping The Fog of War. In that 2003 documentary, Robert McNamara, another former US defence secretary, parried and shimmied in the most diverting fashion. Despite his many linguistic convolutions, McNamara, an architect of the Vietnam War, could not conceal the fact that he had come to offer oblique atonement.

There is no sense of that from Rumsfeld. Some have criticised Morris for not pressing his subject – who was defence secretary during the Afghan and Iraq Wars – on such issues as Abu Ghraib and Saddam's imagined weapons of mass destruction. This is to misunderstand the director's technique.

Though Morris does bark his questions like a football coach troubled by lazy marking, his strategy has always been to allow his often unlovely interviewees to talk themselves towards revelation. There is invariably some moral itch desperate to be scratched.

If Rumsfeld has doubts or uncertainties, they remain very impressively concealed. He is still the clipped man we observed bullying reporters mercilessly in those oddly theatrical press conferences.

None of which is to suggest we are not dealing with an interesting life. As the film reminds us, Rumsfeld has been lurking around the higher reaches of Republican politics for more than 40 years.

The most tantalising moment comes when, during a lengthy career overview, Morris addresses his time in the Nixon White House. For a spell, Rumsfeld was an associate of that notorious gang of high-end hoodlums (John Ehrlichman, Bob Haldeman and so forth) who ended up disgraced after the Watergate scandal. But, craftiest of the lot, Rumsfeld managed to be elsewhere when the messy end came.

Recordings from the White House suggest that, in a sort of back-handed compliment, Nixon felt Rumsfeld was, even by his degraded standards, "a ruthless little bastard". Later, after falling out with George Bush Sr, he managed to catch the eye of a new generation and gain eye-watering degrees of influence.

A sense emerges that, less ideological than mercilessly pragmatic, Rumsfeld and Dick Cheney, his long-term friend and ally, would always engineer a way to endure any political or social firestorm. Indeed, survival and advancement – rather than any sort of conservative crusade – appear to be the driving force in both men's lives.

With this in mind, it would be surprising if, at this late stage in the strange story, Rumsfeld buckled under pressure from a mere film-maker. Morris nevertheless gives him the full treatment: face-front interview via the director's famed Interrotron device; surging chords from Danny Elfman; billowing snowstorms as a visual representation of Rumsfeld's addiction to memoranda. Yet the carapace remains unbroken throughout.

The unavoidable conclusion is that, rather than making any errors in presentation, Morris simply picked the wrong subject. Rumsfeld is occasionally funny, not least when picking over the notorious “known known” speech that gives the film its title. But this is the humour of the scabrous teacher who uses jokes as weapons to humiliate uncooperative students. The humour does not illuminate. To paraphrase Gertrude Stein on Oakland, there’s no there there.

Whereas McNamara was prepared to tease apart the dynamics of Realpolitik, Rumsfeld is more interested in simplifying, obfuscating and distracting. Mind you, he does seem to greatly enjoy the challenge. Maybe it’s not so baffling that he accepted Morris’s invitation. He’s having the time of his life.