LONDON — A midnight blitz of arrests ordered by the crown prince of Saudi Arabia over the weekend has ensnared dozens of its most influential figures, including 11 of his royal cousins, in what by Sunday (Nov 5) appeared to be the most sweeping transformation in the kingdom’s governance for more than eight decades.

The arrests, ordered by Crown Prince Mohammed Salman without formal charges or any legal process, were presented as a crackdown on corruption.

They caught both the kingdom’s richest investor, Prince Alwaleed Talal, and the most potent remaining rival to the crown prince’s power: Prince Mutaib Abdullah, a favoured son of the late King Abdullah.

Prince Mutaib had been removed from his post as chief of a major security service just hours before the arrests announced late Saturday.

All members of the royal family were barred from leaving the country, United States officials tracking the developments said Sunday.

With the new detentions, Crown Prince Mohammed, King Salman’s favoured son and key adviser, now appears to have established control over all three Saudi security services — the military, internal security services and national guard.

For decades they had been distributed among branches of the House of Saud clan to preserve a balance of power in Saudi Arabia, the Middle East’s biggest oil producer and an important US ally.

In the same stroke, the crown prince has cowed businessmen and royals across the kingdom by taking down the undisputed giant of Saudi finance.

And during the last several weeks he has ordered enough high-profile arrests of intellectuals and clerics to frighten the remainder of the academic and religious establishment into acceding to his will as well.

Apolitical scholars who used to speak freely in cafes now look nervously over their shoulders, as the crown prince has achieved a degree of dominance that no ruler has attained for generations.

“It is the coup de grce of the old system,” said Mr Chas Freeman, a former US ambassador. “Gone. All power has now been concentrated in the hands of Mohammad bin Salman.”

Why the crown prince acted now — whether to eliminate future opposition or perhaps to crush some threat he saw brewing — was not immediately clear.

At 32 years old, he had little experience in government before his father, King Salman, 81, ascended to the throne in 2015, and the prince has demonstrated little patience for the previously staid pace of change in the kingdom.

He has led Saudi Arabia into a protracted military conflict in Yemen and a bitter feud with its Persian Gulf neighbour Qatar.

He has taken on a business elite accustomed to state subsidies and profligacy by laying out radical plans to remake the Saudi economy, lessen its dependence on oil and rely instead on foreign investment.

And he has squared off against conservatives in the religious establishment with symbolic steps to loosen strict moral codes, including a pending end to the long-standing ban on women driving.

Crown Prince Mohammed’s haste, however, may now come at a price, because the lack of transparency or due process surrounding the anti-corruption crackdown is sure to unnerve the same private investors he hopes to attract — including through a planned stock offering of the huge state oil company, Aramco.

Saudi Arabian businessmen and royals anxious about the crown prince’s plans were quietly moving assets out of the country even before the arrests.

“Some of these are businessmen with international status, and if they are caught in this web then it could happen to anyone,” said Mr James Dorsey, who studies Saudi Arabia at the S Rajaratnam School of International Studies in Singapore. “How is that going to inspire confidence and attract foreign investment?”

The Saudi Arabian news media, however, celebrated the arrests as a long-awaited cleanup, appealing to populist resentment of self-enrichment enjoyed by the sprawling royal family and its closest allies.

Almost everyone in the capital, Riyadh, and other big cities like Jeddah has heard stories about princes absconding with vast sums that had been allocated for a public project.

The arrests are “a frontal assault on some members of the royal family and the impunity with which they have operated in the past,” said Professor Bernard Haykel who studies Saudi Arabia at Princeton University.

“It was something that had to be done,” he said, even though the absence of a judicial process “sends a chill down the spine of foreign investors.”

US President Donald Trump on Sunday appeared to give a tacit endorsement of the arrests in a phone call with King Salman. A White House summary of the call contained no references to the arrests, and said Mr Trump had praised Crown Prince Mohammed for other matters.

Three White House advisers, including the president’s son-in-law, Jared Kushner, returned just days ago from the latest in at least three high-level Trump administration visits to Saudi Arabia this year.

Nearly 24 hours after the arrests were announced, no Saudi authority or spokesman had identified those arrested or the charges against them.

The Saudi-owned satellite network Al Arabiya reported only that a large number of arrests, including 11 princes, had been ordered by an “anti-corruption committee” that just hours earlier had been formed under the direction of the crown prince.

A royal decree granted the committee powers to detain individuals or seize assets without any trial, process or disclosure.

A list of those arrested began circulating over social media shortly after midnight Sunday, and by Sunday evening senior government officials were reposting the list. News organisations around the region were reporting its contents without contradiction by either the Saudi government or individuals.

In the case of the most politically potent of the detainees, former security chief Mutaib, the Saudi government appeared Sunday to have started a social media campaign seeking to make him the new face of public corruption.

Analysts said the list appeared to reflect individuals with a reputation for self-enrichment and those representing rival power centers within the kingdom.

Others included the power broker who once ran the royal court under King Abdullah, and the owner of one of the biggest private media companies in the region.

But another was a top aide to the crown prince himself — Adel Fakeih — who had been considered a driving force behind the ambitious programme of economic reform, leaving analysts puzzled about the motives.

The history of the house of Saud was sometimes punctuated by violent intrafamily strife in the decades before the founding of the modern dynasty, in 1932.

Since then, the family has maintained its unity in part by spreading its top government roles and vast oil wealth among different branches of the sprawling clan. Most important was the division of the three main security services, which constitute the hard power on the ground.

King Salman, however, quickly named his favourite son, Prince Mohammed, as his defence minister, chief of the royal court, a top economic adviser and deputy crown prince.

Then, this June, the King removed his nephew, Mohammed Nayef, from his position as crown prince and his powerful role of interior minister in charge of the internal security forces, secret police and counter-terrorism operations. Evidently anxious to forestall resistance, the King also placed the demoted nephew under house arrest. A campaign of leaks spread rumours that he had become addicted to painkillers and other drugs.

It was unclear why the crackdown targeted Prince Alwaleed, who is best known for his past and present investments in brand-name Western companies including Twitter, News Corp, Apple and the Four Seasons.

Prince Alwaleed has been a vocal supporter of the crown prince’s plans to attract outside investors to Saudi Arabia. But when a committee of 34 senior family members — known as the allegiance council — approved Prince Mohammed’s elevation to crown prince, one of the three dissenters was from Alwaleed’s branch of the family, the Talals, according to people familiar with the voting.

Mr Michael Stephens, who studies Saudi Arabia at the Royal United Services Institute in London, recalled the bloody purges other leaders in the region have sometimes used to eliminate rivals. What Crown Prince Mohammed was doing, Mr Stephens said, “is a more genteel way of making sure there are no challenges to your power.”

Time will tell, Mr Stephens said, whether the arrests signal a slide into despotism or “whether we will look back and say Mohammed bin Salman is the one guy who saw the wall coming and managed to hurdle it.” THE NEW YORK TIMES