The death of Pol Pot, 23 years to the day after he and the Khmer Rouge seized control of Cambodia, occasioned long backward glances at one of the 20th century's most horrific genocides. It was noted everywhere that the communist reign of terror in Cambodia lasted nearly four years and that at least 1 million human beings -- by some estimates as many as 2 1/2 million -- were murdered in an orgy of executions, torture, and starvation. "In the name of a radical utopia," The New York Times recalled in its long obituary, "the Khmer Rouge regime had turned...