The former crown prince who was arrested, Mohammed bin Nayef, is also a former interior minister and longtime American favorite. He had developed close ties to American intelligence agencies during years of work together while he was interior minister. He was ousted from both of those roles by the current crown prince in 2017 and he has effectively been under house arrest since then.

His younger brother, Prince Nawaf bin Nayef, was also detained.

The crown prince, who acts as the kingdom’s de facto ruler on behalf of his aging father, King Salman, has recently faced grumbling within the kingdom and the broader Muslim world over his unilateral decision to halt visits to Mecca in response to the coronavirus — a move with few, if any, precedents in Islamic history.

Conservatives griped that even as he halted pilgrimages, modern entertainment venues the crown prince brought into the kingdom, like movie theaters, remained open.

One possible motive for the detentions may have to do with the aging of Prince Mohammed’s father, King Salman, 84. The crown prince could be seeking to lock down potential challengers to his own succession before his father dies or abdicates the throne.

None of the princes he detained, however, had given any indication that they intended to challenge Crown Prince Mohammed.

Prince Ahmed is a figure of special gravitas in the family because he is King Salman’s only surviving full brother. Both are sons of the kingdom’s modern founder, and succession had previously passed from brother to brother, until King Salman elevated his own son to crown prince in 2017.

Critics of Crown Prince Mohammed adopted Prince Ahmed as a hero after he appeared to criticize the kingdom’s current policies during an encounter with protesters in London in 2018.