Over the weekend, the crown prince of Saudi Arabia announced the arrests of 11 of his princely cousins, among them some of the kingdom’s most prominent businessmen; he also announced several dramatic changes to top government ministries, including the creation of a powerful new anticorruption committee. Why? Was it a coup? The response to a failed coup? Some kind of purge?

The background to these events is the continuing centralization of power in the hands of the crown prince, Mohammed bin Salman, who is one of King Salman’s sons. Over the past two years he has taken over most of the key economic and security posts and has clearly emerged as the most important operator in the government. The crown prince is also deputy prime minister (under the king, who is also prime minister) and minister of defense. All this at the age of 32.

This steady seizure of power has given rise to resistance within and outside the royal family, and Mohammed bin Salman’s elevation to crown prince was not unanimously supported when the top royal princes met to approve it. In the Saudi system, power has been passed among the sons of the founder of the modern Saudi kingdom, known as Ibn Saud, since his death in 1953. That made the king more primus inter pares than absolute monarch. One king was removed by his brothers (Saud, in 1964), and the system has permitted fiefs: The late King Abdullah was head of the National Guard for decades, and his son Miteb bin Abdullah took it over after his death; the late Prince Nayef served as minister of interior for 37 years and his son came after him; the late Prince Sultan was minister of defense for nearly a half century, and his son Khalid was his deputy.

Crown Prince Mohammed is putting an end to all that, taking some of those posts himself and removing others from the seemingly permanent control of any one branch of the family. All power is going to his branch — to his father, himself and his own allies; one brother is now the new Saudi ambassador to the United States.