The most common word in reports and headlines out of Yemen today is "chaos." The nation once seen as a vital ally in the fight against al-Qaeda is now on the brink of civil war, with Saudi Arabia launching a military operation and the AP reporting that President Abed Rabbo Mansour Hadi has fled the country by boat. Advancing rebels known as the Houthis had previously forced him to decamp from the capital, Sanaa, to the port city of Aden. The reports of his departure are unconfirmed, but the New York Times observes that if he hasn't already left, it's just a matter of time. Here's a sample of some of the complex dynamics at stake: