Baghdad, Iraq—The grave diggers say that the bodies in many of the graves here in a walled-off enclave of the Kirkh Islamic Cemetery, a mile down the road from the big prison, lie twisted in twos and threes. For over 20 years, they report, almost no one has been allowed to visit here, apart from a lone shovel man and the secret police who heaved the bodies from their cars toward the holes in the earth. The head grave digger, Hatem, says he watched these events from behind the wispy eucalyptus trees lining the western wall; he adds that the...