The Houthis are an armed group from northern Yemen that seized the capital Sanaa in 2014 and have fought the Saudi-led coalition since 2015. Their full name is Ansar Allah, or Supporters of God. They follow Zaydi Shia Islam and are backed by Iran. This week they attacked two Saudi airports with drones and ballistic missiles, killing three people and injuring 36. They hit Abha airport on Tuesday and Riyadh’s King Khalid airport on Wednesday. Why now? The Houthis seized the Bab al-Mandeb Strait area last month, a key route for oil tankers. Saudi-backed Yemeni forces then launched Operation Dawn of Yemen to push them back. The Houthis warned airlines against using Saudi airspace. The fighting has spread. Saudi Arabia is asking allies including Syria, Turkey and Pakistan for support. Syria is discussing sending up to 20,000 troops. Analysts fear the war could take on a sectarian tone, with Sunni Syrian troops fighting Shia Houthis. The UN calls Yemen one of the world’s worst humanitarian crises.