Houthi rebels have claimed responsibility for strikes on key Saudi oil facilities. How they've grown their military strength.
Iran is being accused of 'hostage diplomacy' by resorting to incarcerating foreign nationals at a time when sanctions are crippling its economy.
The Houthis belong to the Shiite branch of Islam. The Houthi insurgency began in the early 1990s, spurred in part by growing influence of different Sunni branches of Islam.