Donald Rumsfeld remains a enigmatic and controversial figure. As Secretary of Defense during the invasion of Iraq, a war , blame for the blunder partially rests on his shoulders.

Stephen Colbert had Rumsfeld on The Late Show and used the his own to grill him on the decision to go to war.

Colbert: That leads me to your most famous saying, which is talking about uncertainty in the world. That there are known knowns, things we know we know—and tell me if I get this wrong, because I know it’s your baby—there are known unknowns, things we know we don’t know, and there are also unknown unknowns—

Rumsfeld: They’re the ones that get you.

Colbert: But in this case, isn’t the one that got us... something that, there’s a fourth option that no one ever talks about. Which is the unknown knowns, which is the thing that we know and then we choose not to know them, or not let other people know we know.

Rumsfeld later added the intel the president, joint chiefs and allies had was never for certain: “if it was a fact, it wouldn’t be called intelligence,” he said, leaving Colbert stunned.

Rumsfeld is now 83 years old and is as sharp as ever, and nobody would try to claim that he is dumb or that he doesn’t have a nearly obsessive work ethic. The man has had a prolific career in governmentand has had a hand in the making of history from the Cold War to the post-9/11 era, for better or for worse. Now in retirement, he has even recently developed an app called , of all things.

One of the best ways to get a well-distilled and sometimes entertaining look at the man and the pivotal decision to go to war, not to mention the mishandling of its aftermath, is to watch the. At times it’s an almost eerie look into Rumsfeld’s complex trains of thought.

If anything else, you have to give “Rummy” some credit. Even after being part of the crew that brought about one of the worst foreign policy decisions of all time, he does not hide in the shadows and will sit and answer just about any question anyone throws at him.

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