In Tunisia and Egypt, the popular protests of the Arab Spring sent long-ruling dictators tumbling. But similar uprisings in Syria and Yemen haven't played out that way. Both Syrian President Bashar Assad and Yemeni President Ali Abdullah Saleh have long presided over fractious, complex societies and consolidated their rule through webs of patronage spread across sectarian, tribal lines. The upheavals of 2011 unraveled that status quo in spasms of violence.
Saleh, after months of tribal insurrections, an Islamist insurgency and the defections of key military men, agreed in November to step down from power. Roughly 2,000 protesters have been slain in the process, and it's unclear what sort of political order will emerge in what is one of the Arab world's poorest nations. In Syria, the calculus is even more grim. The Assad regime has bitterly clung to power, confronting protesters weekly with tanks and rocket fire. The bloodshed the U.N. estimates that more than 3,500 have been slain has horrified Damascus's neighbors and allies, with some calling for Assad's departure. The Arab League has demanded an immediate cessation of hostilities and recently leveled sanctions against the Syrian state, an act that appeared only to push Assad and his remaining loyalists further into a blood-soaked corner.