In the first two years of the Trump administration, Sultan Qaboos bin Said, the late ruler of Oman, confronted a stark situation: Iran-backed Houthi rebels were fighting on his doorstep in Yemen, Israel was attacking his Palestinian allies, and Washington was largely giving up on diplomacy in the Middle East.

Instead of seeking refuge in the Saudi Arabia-led alliance of Sunni Gulf states, the veteran leader did something different. First, he invited the Iranian president, Hassan Rouhani, to his palace in Muscat. Then, he welcomed Prime Minister Benjamin Netanyahu of Israel and Yossi Cohen, the head of the Mossad, Israel’s spy agency, for a formal state visit.

In almost any other Arab country today, hosting the leaders of both the Jewish State and the Islamic Republic would be unthinkable. For Qaboos — who died on Jan. 10 after running his country for nearly 50 years — this was simply a way of reinforcing Oman’s status as the region’s most ambidextrous conciliator.

Though he remained little known outside diplomatic circles, Qaboos was, for much of his long career, an indispensable linchpin of the international order. In recent years, he often seemed like a throwback to another era.