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There are known knowns. There are known unknowns. There are unknown unknowns. But there are also unknown knowns - that is to say, things that you think you know that it turns out you did not. – Donald Rumsfeld

In his new documentary “The Unknown Known,” Academy-Award-winning filmmaker Errol Morris (“Fog of War”) sat down with Donald Rumsfeld for more than 30 hours of interviews explaining Rumsfeld's “snowflakes” – a gigantic archive of memos he wrote over five decades in Congress, the White House, at the Pentagon, and in the private sector.

According to Morris, these memos “provide a window into history – not as it actually happened, but as Rumsfeld wants you to see it.”

WATCH AN EXCLUSIVE CLIP FROM ‘THE UNKNOWN KNOWN’ ABOVE

So why an entire feature-length film dedicated to one man?

“Many people are so angry at Rumsfeld that they haven’t even bothered to look at him… Better just to reject him out of hand rather than to actually think about him,” Morris told FOX411. “[He is] endlessly fascinating. Donald is incredibly charming and most certainly well-spoken... This film is Donald Rumsfeld’s picture of himself, an attempt to understand how he sees himself.”

“I was surprised to find out that when pressed about so many of the crucial decisions to invade and the historical events he was a part of, that he reflected so very little about most of them,” Morris said.

“The Unknown Known” posits that the fears and philosophies of Rumsfeld are what led America to war in Iraq. Rumsfeld states in the documentary that “if you wish for peace, prepare for war.” Yet the former defense secretary has no qualms in putting the filmmaker in his place either.

At one point, Morris asks Rumsfeld why “they invaded Iraq,” to which he shoots back: “They? Who is they?” The filmmaker is forced to quickly apologize, re-phrasing the question to reflect why “we” invaded Iraq.

Despite his own anti-war convictions, Morris insists that “The Unknown Known” isn’t a hit job.

“This isn’t a partisan issue, it is about Donald Rumsfeld and the role he played and his explanations for what he did. It’s no secret I had never liked the war in Iraq. I didn’t like it before we went to war, and I don’t like it now. I think it was a mistake to go into Iraq and people across the political spectrum can agree we were sold a bill of goods by the Bush administration,” he added. “But [this] is not about democrats or republicans. It is about policies that did or did not make sense. I wish Americans could return to that way of thinking, I wish we could see things not in partisan terms but in practical terms – what makes sense.”

However, some critics caution that Rumsfeld hardly gets fair treatment.

“Everyone knows Errol Morris for putting Robert McNamara through the wringer for Vietnam, including Donald Rumsfeld. Morris apparently thinks he must only be judged as a heinous war criminal,” said NewsBusters Executive Editor Tim Graham. “No one who grants a filmmaker 30 hours has any expectation it won't be heavily edited. Rumsfeld decided to take Morris on, knowing full well that leftist college professors and historians would show gunk like this in their classrooms. He wants to have his say.”

“The Unknown Known” opens nationwide April 4.

Danielle Jones-Wesley contributed to this report.

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