In a matter of months rebels have swept through Yemen, capturing the capital, forcing the president into exile and causing hundreds of casualties as a simmering conflict has exploded into war. But the causes are complex and confusing. The Houthi rebels are from Yemen’s north, and are now laying siege to the southern port of Aden. Are these geographical rivalries the key? The Houthi are Shia Muslims, supported by Iran. The rest of Yemen is mostly Sunni Muslim, and Saudi Arabia is leading a bombing campaign against the Houthi forces. So is this a sectarian conflict, or even a regional proxy war? And the Houthis have allied with former President Saleh, against Yemen’s current leader who replaced him in the transition after Yemen’s 2011 revolution. Are the roots of the current conflict in the failure of that revolution to deliver progress? Four expert witnesses help to disentangle this complex web and explain what the conflict in Yemen is really about. (Photo: Houthi supporters demonstrate against recent UNSC sanctions. Credit: Yahya Arhab/European Photopress Agency)