“I have lived 78 years without hearing of bloody places like Cambodia,” Winston Churchill was once heard to remark. Now we have all heard of Cambodia. It was there, in the 1970s, that one of the most drastic programs of social engineering in all of history was carried out. The Khmer Rouge, a peasant movement led by utopian leftists educated in postwar Paris, took over the country and began shoveling her population around like wet concrete, with the aim of eliminating forever such bourgeois blights as private property, money, love, education, and religion.

The Khmer Rouge practiced a collective style of leadership, but from 1968 onwards a middle-aged cadre named Saloth Sar emerged as first among equals. In 1970 he changed his name to Pol Pot, for reasons he never explained. It is as Pol Pot that he is known to history, and it is under this name that he is commonly listed with the other ideologically driven gangster-despots – Lenin, Stalin, Hitler, Mao, Kim, and Castro – who brought so much destruction and misery to the world in the 20th century.

Like most Communist leaders, Pol Pot came from a well-off family. His sister became a concubine of Cambodia’s King Norodom, and was at the king’s bedside when he died. Cambodia was at that time a French colony, and Pol went to Paris for education as a young man, arriving in the city on October 1, 1949 – the precise day on which Mao Tse-tung declared the establishment of the People’s Republic of China. Pol fell in with a group of other young Cambodians receptive to the rampant leftism of that time and place. This was the Paris of Jean-Paul Sartre and his circle, the France in which 25% of the electorate regularly voted for the brutishly Stalinist French Communist Party.

Pol seems not to have been an intellectual convert to Marxism. In fact, he seems not to have been very intellectual at all, and probably never read the Communist classics. The Cambodia from which these young men came did not at all resemble the industrialized Europe that had brought forth Marx and Lenin. It was a purely agricultural nation, in which the major institutions were monarchy and priesthood. The revolution that got these young men’s attention was not the Russian, nor even the Chinese one, but the French. Pol’s revolutionary heroes were not Marx and Lenin, but Jean-Jacques Rousseau and Robespierre.

Returning to Cambodia, Pol and his friends soon fell foul of the deeply unlovely government of the young Prince Sihanouk and were obliged to take to the maquis. This was not difficult to do in Cambodia, which had few roads or railways and tens of thousands of square miles of impenetrable forest. As the terrible great-power game of the 1960s played out in southeast Asia, with Russia, China, the United States, and Vietnam all maneuvering for advantage, Sihanouk performed a brilliant balancing act for a while. He fell off the high wire in 1970, however, when his army staged a coup while he was in Moscow. Alexei Kosygin, the Soviet Prime Minister, broke the news to him as they were driving to the airport for the prince to catch a plane to Beijing.

With Zhou Enlai’s support, Sihanouk threw in his lot with the Khmer Rouge, adding monarchical and patriotic glamor to Pol Pot’s resistance movement, which was already at war with the coup regime, headed by Lon Nol. A united-front party and a government-in-exile were formed, known by their French acronyms as, respectively, FUNK and GRUNC. Full-scale civil war broke out, ending with the Khmer Rouge victory of 1975 and the subsequent four-year reign of horror.

Pol Pot’s government was ousted by a Vietnamese invasion in 1979, followed by a 10-year occupation. Popular support for the Khmer Rouge, even as a patriotic resistance movement, rapidly dwindled to nothing. Pol Pot died of natural causes, in the jungle, in April 1998. Cambodia is now a wrecked beggar-nation under the crude and corrupt but non-totalitarian rule of Hun Sen, a former Khmer Rouge foot soldier.

What the reader of a Pol Pot biography mainly wants to know is whether the egregious savagery of Cambodian Communism had its origins, or some of them, in the personality of the leader. According to Philip Short’s account in “Pol Pot: Anatomy of a Nightmare” (Henry Holt, 542 pages, $30), the answer seems to be that it did not.

Pol was in any case never a supreme leader in the classic totalitarian style. The principle of collective leadership was always maintained. Pol seems not to have possessed the spirit of single-minded ruthlessness towards old comrades that characterized those other despots and left them alone at the summit of power. With the exception of the unfortunate So Phim, nobody at the highest levels of the party was purged.

The overriding impression Mr. Short gives of Pol, his comrades, and his government, is in fact one of slovenly incompetence. This was the case even under the apparent rigidities of the 1975-9 period of total power. The Vietnamese invasion, for example, could have been avoided by some adroit diplomacy. The well documented horrors of the forced evacuations, the interrogations, the massacres, were all counter-productive, even by the Khmer Rouge’s own bleak standards. This was amateur totalitarianism.

This judgment, if correct, does fit Pol Pot’s personality, for from all the personal details the author can give us, from Pol’s school work to the hopeless maneuverings of his last days in the jungle, there emanates a strong odor of irredeemable mediocrity. Stalin, Mao, and the rest were awful of course, but given an opportunity to invite one of them to dinner, would you refuse? The sight of Pol Pot and his nutty wife ringing one’s doorbell, on the other hand, would prompt only weary sighs and whispered conjugal debates about whether we might, perhaps, skip the dessert.

Whence, then, did the Cambodian horror come? Philip Short pooh-poohs the thesis popularized by William Shawcross in his 1979 book “Sideshow,” that the gentle people of Cambodia were brutalized by the appalling United States bombing campaign of the early 1970s. He is, I think, correct to do so. U.S. policy towards that nation was stupid and cruel, but there had always been a strain of extreme barbarity in Cambodia. Here is a large provincial city in March 1970, before widespread bombing began: “At dusk, two local MPs arrived from Phnom Penh to try to mediate. They were set upon and killed. Their livers were then cut out and borne in triumph to a local restaurateur who was ordered to cook them. Afterwards pieces were handed out to the crowd.”

Travelers like George Orwell (“Burmese Days”) and Norman Lewis (“A Dragon Apparent”) noted the very singular character of these southeast Asian cultures on the Indian side of the Indo-Chinese cultural divide, their joyless indolence and hideous forest superstitions. Buddhism, with its doctrine of annihilation of the self, may have had something to do with it; rather a lot of selves were annihilated in Pol Pot’s Cambodia. In obedience to the Zeitgeist, Mr. Short, in his prologue, hotly dismisses the notion of biological factors, but you can’t help wondering.

This is the sixth or seventh book about Cambodia that I have read. It left me, as all the others did, envying Churchill those 78 years of blissful ignorance.

Mr. Derbyshire is a columnist at National Review.