THERE’S A PASSAGE in Alan Hollinghurst’s novel The Line of Beauty where he describes the oxymoronic rise of a profligate Lebanese multimillionaire who clambers up into British high society, even as he seemingly loses sight of his business. Hearing that he’s been made lord, another character, who thinks him a misfit, some parvenu foreigner, opines: “I wouldn’t be surprised — there’s a sort of reverse social gravity these days, isn’t there. People just plummet upstairs.” “Anyway, he’s not British, is he?” the protagonist asks. “That’s hardly an insuperable problem,” comes the reply.

The Sassoons — the legendary Jewish Iraqi merchant dynasty — were just such figures, at first enormously successful at their myriad companies before becoming mesmerized by the British aristocracy, into which they were accepted even as their business empire continued its interminable decline. So descendant Joseph Sassoon argues in his new family history of the “Rothschilds of the East,” an exhaustive tome entitled The Sassoons: The Great Global Merchants and the Making of an Empire.

“The price of assimilation,” he writes, was “the global business which had brought them to England in the first place.”

A historian of Saddam Hussein’s Ba’ath Party, familial inquisitiveness came late to Sassoon. As a child, he writes, he used to go “so far as to literally close his ears” whenever his father ventured to educate him about his forebears, no doubt in gloating terms. We should be thankful that the embarrassment wore off, for he is singularly well placed to write this history. Though of a less remarkable branch of the family, Sassoon can read Baghdadi Judeo-Arabic written in Hebrew letters, the lingua franca used to prevent state authorities and rivals alike from snooping on their correspondence — but confounding most historians too. Writing this history, moreover, was practically a family affair. Sassoon could draw on letters and photos and even depend on peer review from a most prodigious family. The upshot is a nuanced and eloquent study, as much a love letter to the Sassoons as an interpretative history of their decline.

We first encounter Sheikh ben Saleh Sassoon, former chief treasurer to the pasha of Baghdad, in extremis, his son David kidnapped in a bid to extort money from the Babylonian Jewry by Baghdad’s new ruler, Dawud, a Mamluk upstart. Luckily for them, in 1830, Sassoon père and fils make a miraculous escape by boat to Basra and from there to Bushir and then — after the sheikh dies — Bombay. (The historian Joseph Sassoon would make a mimetic escape from Iraq in the early 1970s, not long after the Ba’ath Party began public hangings of Jews). The family fortune is lost. But this is just as well, for things are about to get much worse in their homeland. Biblical calamities strike Baghdad, first a plague and then a flood, decimating the town’s population by half.

It was a fortuitous time to arrive in Bombay. Here, conditions were ripe for a modern capitalism to emerge. “Unlike Baghdad,” Sassoon writes, “Bombay was ruled not by a distant emperor but by a joint stock company” answerable to a board in London. True, the East India Company was a corrupt affair that, for the most part, never turned a profit. Even so, in bringing large swathes of the subcontinent under a single authority and establishing a thriving triangular trade with Britain and China, it created a propitious climate for commercial success. The Sassoons also had good luck. The last of the company’s trade monopolies were rescinded in 1833. What’s more, an enlightened former Whig MP who was more welcoming to Jews arrived as Bombay governor the next year. India was up for grabs.

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Over the coming century, Sassoon business interests were to align with British imperial interests, the financial success of the former feeding off the political success of the latter. The Sassoons’ Midas touch was only ever an imperial creation.

It helped that by the early 1830s, the company had transitioned from trade to territory, swapping its leaky trade monopoly for governance proper. Thereafter, it actively encouraged the cotton and opium trades, taking a cut on exports and plugging Britain’s trade deficit; the English had developed a taste for tea, silk, and chinoiserie. For their part, the Chinese became addicted to Malwa opium, and ever larger tracts of land in Bengal came under opium cultivation. When the Qing dynasty threatened to staunch the drain of specie and save its subjects from stupefaction by confiscating opium in Canton and blockading British ships, London’s response was the First Opium War. British victory was a win for free trade.

Enter the Sassoons. The British Empire now had status as China’s most favored nation, not to mention economic and legal privileges in the form of treaty ports and extraterritoriality. The Sassoons made hay while the sun shined, investing in new steamship technology, striking deals with Indian opium producers and Chinese compradors, and diversifying into silk, sugar, copper, pearls, nutmeg, tea, rice, gold, and insurance. In the 1850s, one of David’s sons, Elias, established a bridgehead in Shanghai. Another decade on, the Second Opium War saw opium legalized.

The favors cut both ways. Abdallah, another of David’s sons, offered the British Empire ships to prosecute its war in Abyssinia in 1868. And in Bombay, the Sassoons were Gatsbys avant la lettre, throwing parties straight out of Arabian Nights. Small wonder that they were the toast of the men on the spot.

Cotton was the oil of the 19th century, so it was no accident that the Sassoons, as a business dynasty coming up in the world, were drawn to it. An opportunity arose when the American Civil War caused the Atlantic trade to decline. Again, it was the British Empire oiling the wheels of the Sassoon empire. The supremacy of the Royal Navy kept the Sassoon consignments out of troubled waters, and the Raj’s investments in Indian cotton facilitated its exports to Lancashire and the Gulf. Still, disaster struck when the Confederacy surrendered, sending cotton prices spiraling down and bankrupting four in five cotton traders in Bombay.

Not the Sassoons. Opium came to the rescue. So, too, did their connection with some of the largest banks east of Suez; they had a hand in the founding of HSBC in 1865. By the 1870s, they were the world’s largest opium dealers. Odious as this may seem, we would do well to withhold moral judgement. As Sassoon reminds us, 19th-century sensibilities were rather different than ours. As London and Calcutta saw it, the Empire wasn’t deviously drugging China into oblivion. Opium was legal in the United States, Europe, and indeed Britain, where a doctor’s prescription was introduced only in 1916. In the Middle Kingdom, too, the drug was ubiquitous. That shopkeepers used it as currency points to opium’s status as the Bitcoin of 19th-century China — backed by nothing and just as volatile.

Trade, or “speculation” as it was so often called in the 19th century, was a profoundly risky business: piracy, pilfering, and the perils of capricious local courts and dodgy intermediaries.

The Sassoons’ derisking strategy was to diversify. Here lay the secret to their Brobdingnagian success. At the fin de siècle, the House of Sassoon was as much a commodity as a rentier empire. “Safe as houses,” as they say. In parts of eastern India, the family was effectively an imperium in imperio. For opium farmers, the Sassoons were the state. They also became involved in manufacturing, taking advantage of Peel’s relaxation of protectionist laws. From 1843 on, India could import cotton machinery, much to the chagrin of Liverpool’s producers but to the benefit of the Sassoons, who, by the 1880s, owned more mills than any other Bombay firm.

Unlike the Rothschilds, they never moved into banking. But stereotypes die hard. “Jew bankers” they remained to their English contemporaries and the press. Still, finance was a crucial element. Indeed, what placed the Sassoons in a class of their own was their ability to tap into the world of high finance, thanks to the dispatch of S. D., yet another of David’s sons, to London, where he embedded himself in the city’s milieu of gentlemanly capitalists. As the family crest bore testimony — a Lancastrian rose paired with an Indian poppy — this family straddled East and West.

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But the British connection, says Sassoon, unwittingly set the stage for their subsequent decline. A once sedulous brood succumbed to the seductions of the titled classes, turning the Sassoons into a sorry spectacle of self-indulgent aristos. Here, his book comes to resemble an unconvincing morality play. “Joining the upper classes,” he writes, “was a metamorphosis as fatal to their fortunes as any misjudgment” in Buddenbrooks or À la recherche. The beau monde of baubles, opulence and nonchalance, exuberance and abundance, “drew their attention away from their business.”

It’s a view shared by S. D.’s grandson, the famous war poet Siegfried Sassoon, who disdained his roots:

They made it in the East by dirty trading, millions and millions of coins. They spent it all in drapers’ shops and jewelers and pastry cooks and brothels. They hire large mausoleums and get cremated at Golders Green. They smoke Coronas and worship German royalties and dissolute peers.

I am not entirely persuaded by this tale of bourgeois betrayal. It’s a familiar trope and one as lazy as the character flaw it indicts. For one thing, it seriously underestimates aristocratic inventiveness. Far from an aversion to change, modern royals displayed an addiction to it, as Simon Schama and David Cannadine, among others, have shown. They went down kicking and screaming — and yes, working too. If anything, Britain’s aristocrats were known for their good business sense. After all, they were, as the ruling class, the driving force behind the British Empire — and, for that matter, behind British capitalism in general.

For another, his Protestant pieties about the Sassoons “abandoning their work ethic” only sustain the myth of hard work, which we know was never true. Amassing wealth was never about putting in the hours. Thomas Piketty, one would have thought, had punctured this reassuring Americanism once and for all with his pithy formula, r > g. Income from capital outpaces income from labor. Money makes money faster than you can make it. So much for genteel decline, Britain’s 600 or so aristocratic families have doubled their wealth in the last decade alone, even as real wages have stagnated. Indeed, the peerage boasts scores of successful businessmen whose money works for them rather than the other way around: inter alios, the Cadogans, Grosvenors, Guinnesses, Portmans, Rothermeres, Rothschilds, de Waldens, all welding property and investment portfolios, just as the Sassoons did.

On Sassoon’s account, the early and late Sassoons were chalk and cheese. David, the patriarch, was a pious workhorse based in Bombay who had little time for polite society. He took up British citizenship but displayed little command of English. With Brits, he spoke his native Arabic. His citizenship certificate was signed in Hebrew. Elias, the untiring second-born, took after him, striking out on his own in Shanghai to found E. D. Sassoon & Co. and giving his brother stiff competition in London and Calcutta.

The breakaway would outlive the parent company in Bombay, David Sassoon & Co., which had fallen to his brother Abdallah — or Sir Albert, as he became, a fastidious social climber who liked his “English clothes” and orders of chivalry, among other distractions. When he was made a baronet in 1890, it was a minor triumph. Victoria only rarely overcame her resistance to making Jewish peers. Sir Albert made London his home, leaving Suleiman — both a half-brother and grandson-in-law, on account of a union between great-uncle and niece; the rabbis gave their blessing — to hold the fort in Bombay. When work drove Suleiman to his death, his wife, Farha, assumed control of the firm, becoming one of the first matriarchs to run a modern business empire. Essentially a “free-for-all” when she took charge, she set the company to rights in martinetish fashion, imposing order and rationality to accounts, cash flows, and hires.

But the Stakhanovites could only subsidize the sybarites for so long, Sassoon tells us. At some point, the balance tipped in favor of the latter. The younger Sassoons followed in Sir Albert’s footsteps. “Anglicization” set in. In other words, they became dandies, earning themselves caricatures in Vanity Fair. Joseph, S. D.’s son, found happiness as an antiquarian. There’s a picture of him reclining, as if an Ingres odalisque, on the lawn at Ashley Park, their country house in Surrey. Sir Albert’s son Edward married a Rothschild and became MP for Hythe, a seat once held by his in-laws. An acolyte of the Prince of Wales, later Edward VII, he became a member of his fashionable Marlborough Club set. Their first priority was to party.

Reuben, one of David’s younger sons, also struck a friendship with the prince, becoming his “unofficial bookie.” The two shared a penchant for horse racing. He was welcome at Sandringham, the prince’s country retreat, though not particularly appreciated: “[H]e never opened his mouth, except to put food into it.” For his part, the new Prince of Wales, the future George V, acquired a Sassoon sidekick in Reuben’s younger brother Arthur. Clearly, the younger Sassoons had a thing for kings-in-waiting.

S. D.’s daughter Rachel was cut from a cleverer cloth. She became the first woman in Britain to edit a national newspaper when she took control of The Observer in 1891 and then later The Sunday Times, both bought for her by the Beers, her in-laws who made their fortune as Berlin financiers. Sybil, Edward Sassoon’s daughter, also married up, becoming the wife of the Fifth Marquess of Cholmondeley. Meanwhile, Reuben’s daughter Louise tied the knot with a wealthy cradle-snatcher, the long-retired governor of Newfoundland, Lord Cavendish Boyle, 24 years her senior. Pace Sassoon, one might say that joining the aristocracy made hard-headed business sense.

And not just for the women. Even the starstruck, work-shy Sassoon men did well for themselves. It is true that Frederick, Farha’s brother-in-law who replaced her in a coup, proved an absentee chairman. The day-to-day running was left to the professionals. By all accounts, the latter were a smart lot. David Gabbay, for one, “stood barely five-foot [tall] but was a giant in the counting house.”

On his passing, Sassoon & Co. fell to the “aesthete” Philip Gustave, as gay Brits were called at the time, a trustee of the Wallace Collection and Tate and National Galleries who was partial to Louis XIV and XV marquetry. Sargents hung on the walls of his Park Lane residence. Running the company was left to Cecil Longcroft, a “safe pair of hands.”

E. D. Sassoon & Co., too, remained a thoroughly profitable concern. The second generation was just as industrious as the first. “Almost a replica of his father,” Elias’s son Jacob “never settled in England and worked diligently despite having seriously deficient eyesight and an invalid wife.” He was aided by his brother-in-law Jacob David, “a capable manager” who returned the family mills to profit. The business then fell to Jacob’s debauched nephew Victor, Third Baronet of Bombay.

Victor was a voyeur. His private papers are an archive of thousands of snaps of women, many of whom posed naked for him. He enjoyed his annual luxury cruises and racecourses: “There is only one race greater than the Jews and that’s the Derby.” There were rumors of affairs with the ebullient Paulette Goddard as well as the enigmatic Marlene Dietrich — the one a vivacious comic familiar from Chaplin, the other a sultry Teutonic siren. He evidently wasn’t very discriminating; their only common denominator, it seems to me, was glamour. Conjugal life came late to him. His was the last in a long line of May–September Sassoon marriages. Aged 77, he took up with his thirtysomething Texan nurse in Nassau. The Bahamas had the dual attraction of being a British colony as well as a tax haven.

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For all his philandering and hobnobbing, though, it wasn’t “complacency” or “the glitter of British society,” as Sassoon has it, that did in Victor’s empire. Rather, it was dire circumstances and bad luck. Just as Sassoon understates the role of empire in augmenting the family’s fortunes, falling back instead on bromides of trust, instinct, and efficiency, so too does he breeze past the overlap between the imperial endgame and the fall of the Sassoons.

The fatal flaw was backing the wrong horse: China and not India. Understandably. In the 1920s, India appeared to be the bigger trouble spot. The Sassoons’ cotton interests were threatened by a slump and a wave of strikes. Victor’s hauteur was of little help. Instead of cutting a deal with the unions demanding a 48-hour work week, he held out for nothing less than 60. From his perch at the Indian Legislative Assembly, he endeavored to keep the rupee down and the Reds out, foaming at the mouth over communists “bringing about the suffering of all the cultured classes.” India was turning red, he decided. Better, then, to move to China: “Bolshevism could never flourish there.” Like so many Sassoons, a historian by training — Victor read history at Cambridge, the “aesthete” Philip at Oxford — prognostication wasn’t his strong suit.

At first blush, there was little wrongheaded about the move. He ensconced himself in an expat colony, Shanghai’s International Settlement, in 1931. Taxes were lower than in India. Nationalism was yet to raise its ugly head. The returns on capital were staggering: the Sassoons’ 30-odd properties appreciated by 2,500 percent in the 40-odd years to 1920; by 1937, they were worth $2 billion in today’s money. One could, moreover, live above society rather than in it. Admittedly, the proles on occasion got ideas above their station, such as when the city’s first skyscraper, the Sassoon-owned Cathay Hotel, “the Claridge’s of the East,” was pressured into abandoning its questionable preference for lavatorial apartheid: loos had been marked either “Gentlemen” or “Chinese.”

Sensibly, the Sassoons curried favor with the anticommunist Kuomintang. Victor counted Chiang Kai-shek’s brother-in-law among his close friends. Unluckily, however, KMT rule wasn’t the pillar of stability it was made out to be. As corrupt as it was collaborationist during the Second Sino-Japanese War, it quickly lost legitimacy in the eyes of the Chinese people. China, which was on the silver standard, had already plunged into a depression following the bullion outflow caused by the United States’ Silver Purchase Act of 1934, which pushed up silver prices to the benefit of Midwestern miners. Shortly after, in 1937, Sassoon buildings took an all-too-real battering in the Battle of Shanghai, “Stalingrad on the Yangtze,” as it were. By the time Shanghai fell to Mao in May 1949, the Sassoon property portfolio was worthless. The nationalization of the company’s assets was just the coup de grâce. “Well, there it is,” Victor remarked, “I gave up India and China gave me up.”

With Victor’s death in 1961, E. D. Sassoon & Co. slipped from the family’s hands. Likewise, Longcroft’s two decades at the helm of the other Sassoon company from 1928 on were plagued not so much by aristocratic ennui but external events: the Depression, involution of trade, the firm’s failed stab at trading commodities from Buenos Aires.

An early setback had been the collapse in opium prices during the last quarter of the 19th century as Chinese producers substituted opium for wheat. If oversupply was killing the trade, regulation dealt the death blow. A Quaker campaign pushed for the suppression of the opium trade in the Commons. It was, in part, on the strength of testimonies from Sassoon officials that the trade persisted for a while; Gladstone’s royal commission of inquiry was informed in 1893 that for the Chinese, opium was “a sort of necessity of life.” But Chinese nationalist sentiment could only be ignored for so long. With the Opium Edict of 1906, the imperial government promised to eradicate the drug in 10 years.

In the final analysis, the Sassoons’ success hinged on the success of imperial globalization in brigading British rule and naval supremacy with Indian peasants, Jewish merchants, and Chinese consumers. Once the imperial system unraveled, so too did the fortunes of the Sassoons. The latter was ever so bound up with the former. Throughout his book, Sassoon recognizes this, but in the end, he plumps for other explanations: family rivalry, “crippling” inheritance taxes, and, above all, the corrupting influence of the indolent aristocracy. Indeed, one of Sassoon’s admirable qualities is that he supplies all the material to reach conclusions completely at odds with his own.

The elisions are nevertheless noteworthy. Sassoon is drawn to neat moral narratives, which come at the expense of economic explanations. His comparison with India’s Tatas is instructive. Whereas the Sassoons lived it up, the Tatas burned the midnight oil in their mills. One house collapsed; the other lives on to this day, a thriving enterprise at that: QED. But that isn’t the half of it. The Tatas succeeded because they bet on the right horse, throwing their weight behind Congress, ingratiating themselves with India’s new rulers at independence. Unlike Chinese communism, Indian socialism proved essentially toothless. The Tatas’ wager paid off, and they came to secure contract after contract under Nehru’s license raj, tailored to benefit them. Likewise, while the Sassoons settled in Shanghai, where expropriation awaited them, the more longevous Kadoorie family decamped to Hong Kong, which remained a British enclave for another 50 years, safeguarding their wealth.

All the same, the tale of bons vivants makes for riveting storytelling, if not terribly sound business history. Readers will take away a great deal of British and Asian modern history from Sassoon’s globetrotting account — not to mention decorating ideas worthy of How to Spend It and, more realistically as we brace for stagflation, some interesting recipes, a potpourri of East and West: hamod with meatballs and sour beetroot for hors d’oeuvres; tabit, “a signature Baghdadi-Jewish dish of stuffed chicken buried in rice, cooked overnight”; “Sassoon curry,” still a niche favorite on Shanghai’s Bund; and custard pudding. Wash it all down with Victor Sassoon’s signature “Barbara,” one of his more inspired annual cocktail creations: “1/2 vodka and 1/2 sour cream with a dash of crème de cacao.”

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Pratinav Anil, a historian from Bombay, is unlikely to succumb to the beguilement of Britain’s indolent aristocracy.