By the middle of 2003, as it became clear that the American invasion of Iraq would result not in a quick “mission accomplished” but a long, bloody occupation, a certain narrative of what went wrong began to take root in some precincts of the anti-war left. The decision to invade Iraq, this story went, was the result of the government falling under the sway of a dangerous ideology, called neoconservatism. The neocons, as they were often derisively called, believed in the naked assertion of American power—in a kind of imperialism, really, which gave America the right to invade other countries...