NO ONE is quite sure what to call it. The arrest of scores of people in Saudi Arabia on November 4th has been variously dubbed a coup, a counter-coup and a purge. Those detained range from billionaire businessmen, such as Prince Alwaleed bin Talal, to a contender for the crown, Prince Mutaib bin Abdullah. “Saudis do not know what happened,” says a professional in Riyadh, the capital. “It is a shock.” One thing, at least, is clear: power is now concentrated in the hands of the young crown prince, Muhammad bin Salman, who orchestrated the blitz in the name of his frail 81-year-old father, King Salman.

For decades, Saudi kings tried to forge consensus within the sprawling royal family. Change was incremental and power was balanced delicately, particularly among members of the so-called Sudairi Seven branch—the sons of King Abdel-Aziz, the founder of the state, by his favourite wife, Hussa bint Ahmed Al Sudairi (see family tree). One Sudairi, Prince Sultan, served as defence minister for 48 years. Another, Prince Nayef, and later his son Muhammad, controlled the interior ministry for more than four decades. And from 1963 the National Guard was the preserve of Prince (later King) Abdullah and his clan.

All three positions are now under the control of Prince Muhammad or his allies. The crown prince became defence minister just hours after his father (also a Sudairi) ascended the throne in 2015. In June the ruling duo sacked the interior minister, Muhammad bin Nayef, a former crown prince, and placed him under house arrest. On November 4th they finished the job by sidelining Prince Mutaib, the second son of the late King Abdullah, who had once been mooted as a possible future monarch. They also announced several changes to government ministries and the creation of a new anti-corruption committee, which approved the arrests—and is headed by Prince Muhammad, of course.

The iron throne

To some, the shake-up is a sign of the crown prince’s vision. Prince Muhammad has laid out a sweeping agenda that aims to wean the kingdom off oil, modernise the economy and attract foreign investment. He hopes to sell off a portion of Aramco, the state-owned oil company, next year and recently announced plans for a $500bn economic zone, called NEOM, to be staffed by robots.

The old, sclerotic system of governance would have made it difficult to implement such reforms; allowing corrupt and privileged princes to continue milking the kingdom would have undermined them. “You cannot reform the country without a rupture with the past,” says Bernard Haykel of Princeton University.

Just as ambitious are Prince Muhammad’s efforts to loosen stifling moral codes, enhance cultural life and promote a “moderate Islam open to the world and all religions”. That approach is a stark contrast to the puritanical version of the faith that the kingdom has long exported around the world. Yet in this area he has already made progress. A royal decree, proclaimed in September, will allow women to drive next year, ending a ban that has lasted decades. Saudis may soon be allowed to go to the cinema, too.

“In order to do something like that you need to have a firm fist,” says Hoda al-Helaissi, a member of the Shura Council, the royally appointed proto-parliament.

The palace has been clear: support the reforms or face the consequences. With more than their usual zeal, the authorities have clamped down on dissent under King Salman. Those who tweet criticism of Prince Muhammad’s agenda have been thrown into prison. In September police detained dozens of critics, from Muslim clerics to human-rights activists. Last year the crown prince curbed the mutaween (religious police). He has told other Islamic leaders to speak up for religious toleration. The Council of Senior Scholars, Saudi Arabia’s top religious body, backed his latest round-up, saying that Islamic law “instructs us to fight corruption and our national interest requires it”.

There is a strong whiff of populism to the latest crackdown. As part of the reform drive, Prince Muhammad aims to cut subsidies for things such as energy and water. But ordinary Saudis have bristled at the austerity, causing the government to backtrack. Salary and benefit cuts for state employees were reversed in April and other cuts have been postponed. Some Saudis questioned why they should make sacrifices while rich princes continue to feed at the kingdom’s trough. (Prince Muhammad himself is reported to have bought a $500m yacht in 2015.)

The round-up of fat cats has gone down well on the street, especially with young Saudis: 70% of the population is under the age of 30. “The noose tightens, whoever you are!” read the headline in one Saudi-owned newspaper. Many rejoiced at the downfall of Prince Turki bin Nasser, the wheeler-dealer behind controversial arms deals between Saudi Arabia and Britain. Prince Alwaleed was mocked for his jet-setting lifestyle.

And despite grumbles over austerity, young people are largely supportive of Prince Muhammad, with some comparing him to Lee Kuan Yew, the authoritarian who modernised Singapore. It therefore came as something of a surprise to Saudis when foreign investors raised concerns over the arbitrary nature of the arrests (see next story).

The domestic turmoil comes at an already fraught moment for Saudi Arabia. Its two-and-a-half-year war in Yemen, meant to crush Houthi rebels who ousted the Yemeni government in 2015, has turned into a costly quagmire. Though the Houthis have lost territory, they still control most of northern Yemen, including the capital, Sana’a. On November 4th the Saudis intercepted a ballistic missile fired at Riyadh. Adel al-Jubeir, the Saudi foreign minister, blamed Iran for supplying the rocket and Hizbullah, its Lebanese client militia, for launching it from Yemen. “We see this as an act of war,” said Mr Jubeir.

More such attacks are likely from Yemen, say analysts, which, in turn, may lead to more foreign adventurism. Prince Muhammad is also embroiled in a diplomatic assault on Qatar, which was meant to force the gas-rich emirate to drop its support for Islamist groups. Instead, it has divided the Gulf Co-operation Council and caused Qatar to turn for help to Iran, which is gaining influence across the region. Indeed, on the same day as Prince Muhammad’s shake-up, Saad Hariri, Lebanon’s pro-Saudi prime minister, resigned. Mr Hariri made his announcement from Riyadh, blaming Iran’s malign influence on his country (see article).

There are some who think the prince’s missteps abroad will undermine him at home—and that the recent purge reflects nervousness about internal resistance. But other royals seem too intimidated, fragmented or lazy to challenge him. Prince Mutaib aside, the blacklisted officials are a weak lot.

Still, the arrests send a message to would-be critics or challengers. Prince Muhammad, more than any other leader in decades, has fashioned himself the sole maker of Saudi policy. If his plans falter, Saudis will know whom to blame.