On the page, Carr is a bellicose companion. In person, he’s no less fervent but a lot jollier. Lean and longhaired, this boyish-looking 46-year-old makes it clear that it’s not easy being a Renaissance man. “People want one thing from each person and nothing else,” he says with a shrug. Carr’s reputation rests on “The Alienist” and its sequel, “The Angel of Darkness,” best-selling psychological mysteries set in New York City in the 1890s. “Everyone associates me with these period mystery novels, which were really just designed to make a little money on the side” while he pursued a career in military history and public policy at Foreign Affairs magazine and the Council on Foreign Relations. But once “The Alienist” became a best seller in 1994, history and policy studies took a back seat. As a result, he frets that people won’t take him seriously as a military historian.

Not to worry. No one encountering the erudition on nearly every page of “The Lessons of Terror” is going to mistake the author for a dilettante. Conceived as an introduction for the general reader, written and edited between September 11 and Christmas, “The Lessons of History” is so earnest, so well informed and so outrageous–what does he mean, terrorism always fails?–that almost any reader will find something to love and something that will make you want to throw the book across the room. It is, in short, pure Carr.

He’s been a contrarian as far back as high school, when he fell in love with military history at a Quaker prep school in New York City. In similar fashion, he recently abandoned the city, where he’d spent almost his whole life, and moved to a farm near Albany, N.Y. He left, he says, because the city got too nice, too clean. “There’s just no romance in it anymore. I’m better off up here. It’s a way of life I understand better,” a point he proves implicitly when he serves a lunch of wild turkey that he shot himself.

Carr makes good company in person and on the page because you never know what he’s going to say next. Secretary of Defense Donald Rumsfeld is a hero: “A year ago if you’d said, ‘You’re going to be a big Don Rumsfeld fan,’ I would’ve said, ‘Hmmmm, I don’t know.’ But he’s done a wonderful job and he’s forced the Pentagon to do a wonderful job–against its will.” In the next breath, he’s arguing for the dismantling of the CIA: “Obviously I am no leftist, but that organization has undermined the moral authority of this country to the point where we are well hated in parts of the world where we shouldn’t be.”

Carr originally sketched out the ideas in “The Lessons of History” in a 1996 essay published in the World Policy Journal, an article bitterly denounced by experts on terrorism, who labeled it extreme. But since September 11, those ideas–such as the idea that terrorism is a problem for the military and that sponsoring states should be held responsible for the terrorists who live within their borders–have coincidentally become the driving forces behind the Pentagon’s prosecution of the war in Afghanistan. Suddenly, Carr looks like a man with all the signs in his favor, right down to the one that hangs outside the ice-cream shop in his little New York town: WELCOME HUNTERS.

The Lessons of TerrorBy Caleb Carr (Random House)