The victory of South Yemeni secessionists in Aden is another humiliating setback for the Saudi war effort and its commander Crown Prince Mohammed bin Salman. The Saudi-backed government of Abdu Rabbu Mansour Hadi has lost its capital, further undermining its shaky claims to legitimacy. The Saudis' closest ally, the United Arab Emirates, was partially responsible for the secessionists' gains. The Houthis and Iran are the strategic winners.

The Emiratis have built up the southerners for several years in Aden. When Abu Dhabi withdrew much of its own forces from the port city this summer, the secessionists were free to move against the Hadi government and rapidly prevailed. The Saudis will try to paper over the quarrel within the anti-Houthi coalition, but the damage is done to Hadi’s weak regime as well as to the Saudi-Emirati alliance.

The fiasco is the latest in a long stream of strategic blunders by the Saudi leadership. The initial response to the Houthi rebels' takeover of Sanaa five years ago was a botched effort to intimidate the Zaydi Shiite group with air power. Operation Decisive Storm was anything but decisive. The lack of a credible strategy and endgame was apparent to several key Saudi allies like Pakistan and Oman, who opted not to join the war. Coalition management was an early casualty of an inexperienced leader.

The war settled into a quagmire with horrific humanitarian consequences for the Yemeni people. Children have been especially hurt, with massive malnutrition and disease costing millions the chance to have a normal childhood. The long-term consequences for an entire generation has only just begun to take their toll. The Saudis bear the lion's share of responsibility for this catastrophe in the poorest Arab country.