Taken from his insightful essay Notes on Nationalism. A quick Google search brought up the Shanghai massacre, but no reference to "boiling people alive"—which would be extremely unworthy hyperbole, if that's all it is. If it's simply an exaggerated version of events that he repeated, where did he hear it from? Was it reported in a sensationalised manner in English media or what?
The Shanghai massacre, which took place in April 1927, was a fairly significant event in the history of the civil war between Nationalist and Communist forces in China; by killing what were probably fairly large numbers of urban communists in one of the most notably left-wing cities in China, Chiang and his supporters arguably helped tilt the balance of power within communist ranks towards the peasant rebel forces led by Mao Zedong.
Nonetheless, exactly what happened in Shanghai that month, how many died, and how they did so, remains very difficult to establish. The massacre was chaotic, and it was carried out not only by Chinese nationalist forces but also by criminal elements in Shanghai who worked alongside them. No records were kept, no bodycounts were made – historians' estimates of deaths vary from a couple of hundred all the way up to 10,000 – and the handful of western reporters in the city at the time seem to have had little access to firm details, and to have written nothing at all about any "boilings" at the time. I have searched digitised editions of newspapers published in 1927 in both the US and UK fairly extensively without finding contemporary reports that suggest any such executions took place, and Orwell's account, rather notably, dates only to 1945.
It certainly does seem to be true, however, that stories of such killings did circulate at a later date. Here it's helpful to turn to Roy Rowan's memoir Chasing the Dragon, a book written by a long-lived American foreign correspondent who reported the Chinese revolution for Time-Life. Rowan (1920-2016) was far too young to have reported the Shanghai Massacre when it took place, but he was in the country a couple of decades later, and that put him on the spot in time to pick up rumours of what had actually taken place back then.
One of the characters that Rowan wrote about was Du Yuesheng, better known as "Big Ears" Du, a gangster who ran much of the sex trade in Shanghai during the 1920s and was leader of an organised crime group known familiarly as the Green Gang. This group acted, at times, as the enforcement arm of local Nationalist leaders, and, according to Rowan, it was "Du's thugs" who carried out most of the killings in 1927:
Heads rolled in the gutter like ripe plums," according to an eyewitness [and] a number of Communist railway workers were also cooked alive in the boilers of their steam engines... Du's reward for masterminding the massacre was the tight hold he still enjoyed on the city's variety of vices, from the opium section of Nantao, to the waterfront bars of Hongkew, lined with smiling Chinese singsong girl and White Russian 'hostesses'.
So Rowan, who arrived in Shanghai in July 1946, picked up a story that could plausibly match Orwell's perhaps-exaggerated "hundreds" of deaths by boiling, written the previous year. Where, though, might such accounts have actually originated from?
I should make clear that there is certainly nothing to absolutely invalidate the idea that this unpleasant method of execution actually was employed in 1927. But with no contemporary accounts suggesting that such killings did take place, it's worth looking a bit further afield. The first thing to say in this respect is that wild stories about people being boiled alive in China certainly did circulate throughout this period, and were very arguably one fragment of a much broader western Orientalist discourse derived from popular notions of exotic, barbarous Chinese cruelty that dated back at least a century. The infamous French novel The Torture Garden (1899), Bear's underground Actual Photographs of Chinese Executions (c.1915), and the circulation of images showing the 1904 execution of a criminal named Wang Weiqin by the "death of a thousand cuts", all drew on (and contributed to) this trope, and one consequence was the circulation of demonstrably unreliable tall stories alleging deaths by boiling in the first quarter of the 20th century. For example, the Russian diplomat Roman Romanovich (Baron Rosen) recorded that stories circulated at the time of the Boxer Rebellion (1899-1901) that one of his colleagues, Michael de Giers, had been boiled alive by the rebels; in fact, De Giers survived the uprising to die in 1932. Similarly, the British journalist Arnold Wright, writing in 1908, noted that other accounts (in circulation at the time of the siege of the foreign legations in Beijing, during the rising) confidently reported "the boiling alive in oil of every foreign man, woman, and child in the capital." Again, no such killings actually took place. Rather, their circulation was attributed at the time to a shadowy figure nick-named "The Shanghai Liar".
So all this background perhaps helps us understand how stories of atrocities in which people were boiled alive might plausibly have begun to circulate as a result of the Shanghai Massacre. But how did George Orwell, who had never visited China, get hold of the tale earlier than did Roy Rowan, who actually was in Shanghai in 1946? As it happens, there is a very plausible, and very fictional, explanation which seems to locate the origins of this specific story in the mind of the renowned French novelist André Malraux, whose best-selling La Condition Humaine (translated into English as Man's Fate) – a book set in Shanghai in 1927 – contains a passage in which a wounded Chinese man
began to mumble. It was too dark now for Katov to make out his features, but he heard his voice, he felt he was becoming coherent. Yes – "... don't shoot, they throw them alive into the boiler of the locomotive," he was saying... the sentry was approaching again. Silence, except for the pain.
Exactly where Malraux got this detail from, or how he dreamed it up, is not known. He was in Cambodia – then part of the French colony of Indochina – in 1926, and later claimed to have crossed over into China and experienced the horrors of the civil war period at first hand. But this, according to Anne Lijing Xu, was a fabrication; Malraux was in fact at home in France at the time, and did not first visit China until 1931. Given this, it seems well worth noting that, in the opinion of his biographer Oliver Todd, the China that he portrayed was
neither true in its detail nor false overall, but it is nonetheless imaginary. Malraux cannot quite break clear of a conventional idea of China with coolies, bamboo shoots, opium smokers, destitutes, and prostitutes."
And exotic methods of execution? One cannot help but wonder.
What matters, nonetheless, is that La Condition Humaine was a colossal success, winning the Prix Goncourt in 1933, and going on to sell in excess of 5 million copies. Given its very wide circulation, it seems more than plausible that Orwell read it, and that some memory of doing so might have formed the basis of his passing reference to the boiling deaths of Shanghai. Certainly no account that I have read takes this story back any further than Malraux, who published in 1933.
Sources
Baron Rosen, Forty Years of Diplomacy (1922)
Timothy Brook et al, Death By a Thousand Cuts (2008)
André Malraux, La Condition Humaine (1933)
Roy Rowan, Chasing the Dragon: A Veteran Journalist's Firsthand Account of the Chinese Revolution (2004)
Harold Schiffrin, Sun Yat-Sen and the Origins of the Chinese Revolution (1968)
Oliver Todd, Malraux: A Life (2005)
Arnold Wright, Twentieth Century Impressions of Hong Kong, Shanghai and Other Treaty Ports of China (1908)
Anne Lijing Xu, The Sublime Writer and the Lure of Action: Malraux, Brecht, and Lu Xun on China and Beyond (2007)
As you noted, looking up sources (contemporary and modern) about the anti-communist repression of the 12 April 1927 by Chiang Kai-shek and its allies does not reveal examples of people being boiled alive. There are reports (and pictures) of communists and communist sympathizers being shot, decapitated, strangled, and buried alive, but not boiled. The repression continued for several months and the total number of victims is estimated to be up to 2000, with some sources claiming that 5000 people were killed (Smith, 2018). The closest I could find about a mass execution by fire is the death of 300 Buddhist monks, reported for instance by Le Gaulois (and other western newspapers) on 4 March 1928:
Shanghai, 2 March. According to reports here, more than three hundred monks were locked up by Communists in a temple in the town of Lei-Yang, in southern Honan, and burned alive. The town itself is said to have been almost completely destroyed. Many inhabitants, several hundred, are said to have been killed after atrocious torture. These acts of banditry are attributed to communist peasants who were joined by several hundred former soldiers of one of the leaders of the Han Keu army, General Chang Chen Chou. It is rumoured that an army, commanded by General Pei-Tcheng-Chi, military chief of Kouang-Si, is on the march to attack the bandits.
But the perpetrators here were (allegedly) communists.
There is, in fact, a famous source for the "communists boiled/burned alive" story: André Malraux's novel La Condition Humaine (Man's Fate), winner of the top literary prize Prix Goncourt in 1933. The story takes place in Shanghai during the events of March and April 1927, and in one celebrated scene of the novel, one of the characters, Katow, a Russian communist, is captured by Chinese nationalists, who are in the process of killing their prisoners one by one by throwing them alive into the boiler of a steam locomotive. Katow plans to commit suicide by using a cyanide capsule but gives it instead to two other revolutionaries to spare them the torture, and he dies a hero. [For the record, my grandfather, an engineer who had worked with furnaces in the 1920-1930s, found that part of the novel absolutely ludicrous].
Let's note here that while Malraux had lived in Indochina, he was not in Shanghai in 1927 and he only briefly visited China in 1931 before writing the novel. Most of the characters in the Condition Humaine are European or mixed-race and his China (and the few Chinese people he describes) is largely stereotypical (see Xu, 2007). He drew some of the content of the book from two sources, French journalist Georges Manue and Henk Sneevliet aka Maring, a representative of the Komintern (Leblon et Pichois, 1975). Whether he heard the boiler story from someone or made it up entirely is anyone's guess. Some critics were doubtful when the book was released (see Closson, 1933).
Orwell and Malraux had a few things in common: both were left-wing writers who had spent time in Asia (in Burma for Orwell) and later fought in the Spanish Civil War. In 1934, Orwell had learned about Malraux's novels about Asia and had asked a French publisher about the possibility to have Malraux write the preface of his own Burmese Days (letter of 9 October 1934) (the book was published in French but without a preface by Malraux). In 1945, Orwell, now a correspondent in continental Europe for The Observer, met Malraux in Paris. Malraux was now an advisor to de Gaulle and less of a left-winger. Orwell found Malraux friendly, and again, asked him if he could write the introduction to the French edition of Homage to Catalonia (it did not happen)(Meyers, 2010).
We still do not know with absolute certainty where Orwell got his idea of hundreds of boiled communists. But at least he was in contact and admired a celebrity writer who made that claim in a much acclaimed novel.
Sources