It all began more than a decade ago. Saudi Arabia and the United Arab Emirates were the pillars of a coalition created to fight the Houthis who had taken control in Yemen. Over the years, that mission failed. Then the UAE set out to pursue its own long-term interests, by supporting and arming a group called the Southern Transitional Council in the south of Yemen. But Riyadh stepped in to disrupt what it saw as a national security threat, after the council took control of areas close to its borders. The UAE was given 24 hours' notice to withdraw, that it agreed to. What does all this mean for the future of Yemen?