Yemen looks close to civil war. At the weekend Houthi rebels, mainly Shias from the north, attacked Taiz, the third-largest city. They are moving towards Aden, where the internationally recognised president, Abd Rabbo Mansour Hadi, now resides; the Houthis captured the capital, Sana’a, in September. Mr Hadi accuses them of doing Iran’s bidding and yesterday his foreign minister called on Gulf states to intervene on his side. The rebels’ leader says Mr Hadi is working with Sunni extremists to destabilise Yemen, a desperately poor nation of 24m people. So yet another Arab country is being torn apart after the toppling of a president (Ali Abdullah Saleh left power in 2012; an initially successful transition fell apart). Extremists benefit from the chaos. All American officials have left, making it harder for them to oversee drone strikes against a local branch of al-Qaeda. And Friday’s bombing of two Shia mosques in Sana’a, which killed 137, was claimed by a group calling itself an affiliate of Islamic State.