'Graveyard of Saudi ambition': Why the Houthis remain Riyadh's biggest headache

Yemen has long been described as the graveyard of Saudi ambition. And this month Riyadh learnt its latest lesson.For more than a decade, the kingdom has spent billions of dollars, deployed advanced weapons and invested enormous political capital in trying to contain the Houthi movement on its southern border. What began as a northern Yemeni insurgency has developed into a formidable military force capable of launching missiles and drones across the region and threatening one of the world's most important shipping routes.The latest setback came this month, when Houthi forces captured the Red Sea port of Mocha and then advanced towards the strategic island of Perim, also known as Mayyun, at the mouth of the Bab el-Mandeb strait.Mocha was not the whole story.