Saudi Arabia has sacked its top military commanders, including the chief of staff, in a series of late-night royal decrees.
Saudi King Salman also replaced the heads of the ground forces and air defences.
The news was published by the official Saudi Press Agency, but no reason for the sackings was given.
They come as the war in Yemen, where a Saudi-led coalition is fighting rebels, is nearing the end of its third year.
Crown Prince Mohammed bin Salman is believed to be behind various recent shake-ups in the country.
Last year dozens of prominent Saudi figures, including princes, ministers and billionaires, were locked up in Riyadh’s five-star Ritz-Carlton hotel as the prince led a drive against corruption and abuse of power.
By Sebastian Usher, BBC Arab Affairs Editor
This is another sweeping overhaul of Saudi institutions that has become the hallmark of the reign of King Salman, although the driving force is once again his son and heir, Crown Prince Mohammed bin Salman.
The Saudi intervention in the Yemen conflict was his initiative – one of the first indications of just how dramatically he was going to break away from the country’s traditional caution.
And it has so far failed, even if it has forced the Houthi rebels out of the south of Yemen and allowed the ousted government to re-establish a foothold. The cost for Yemen itself has been a humanitarian disaster, while it has also drained Saudi coffers in a time of austerity.