It was one of the most striking, and least expected, interventions in all the turbulence unleashed by the Arab Spring.
King Abdullah announced that Saudi Arabia was recalling its ambassador to Syria for consultation. In a statement read on al-Arabiya television, he demanded that the Syrian government stop "the killing machine" and institute "actual reforms". What was happening in Syria, he said, was "not acceptable to Saudi Arabia".
This was a dramatic coming off the fence – a sign that Saudi Arabia's patronage of President Bashar al-Assad is under possibly terminal strain, but a sign also that the balance of advantage, both in Syria and the region, may be shifting irrevocably. Within hours of the King's statement, Bahrain – which might raise a few eyebrows – and Kuwait announced that they, too, were recalling their ambassadors from Damascus. Turkey's Foreign Minister is due in Syria today, carrying a "tough" message for Mr Assad.
But it is the Saudi intervention that marks the potential tipping point. Until yesterday, Saudi Arabia had remained uneasily on the margins as the euphoria of the Arab Spring gave way to the harsh realities of summer. Its rulers had little to say. Their sole action had been to dispatch troops to Bahrain to help the authorities crush anti-government protests. In so doing, they were shoring up the power of the kingdom's Sunni minority against the Shia majority, and defending the status quo in their own backyard. Now, they clearly sense that their own self-interest lies elsewhere than in solidarity with the Syrian government of Mr Assad.
But there is a conundrum here. Can Saudi Arabia back reforms in Syria without precipitating similar demands closer to home? And if it cannot, what then? The winds of change may yet sweep across Saudi sands.