Finally, there is a peace deal of sorts in the Middle East. Not between Israel and the Arabs, but between Saudi Arabia and Iran, which have been at each other’s throats for decades. And brokered not by the United States but by China.

This is among the topsiest and turviest of developments anyone could have imagined, a shift that left heads spinning in capitals around the globe. Alliances and rivalries that have governed diplomacy for generations have, for the moment at least, been upended.

The Americans, who have been the central actors in the Middle East for the past three-quarters of a century, almost always the ones in the room where it happened, now find themselves on the sidelines during a moment of significant change. The Chinese, who for years played only a secondary role in the region, have suddenly transformed themselves into the new power player. And the Israelis, who have been courting the Saudis against their mutual adversaries in Iran, now wonder where it leaves them.