By thwarting regime change in Yemen, the United States risks empowering al-Qaeda and alienating a nation.Yemen is a complex country that has been under considerable turbulence. Yet understanding Yemen tells us a great deal about the contemporary Middle East, Obama administration foreign policy, and the direction of the “Arab Spring.”While Americans may think that their government’s recent policies and leadership have made the United States more popular in the region, the truth — as polls show — is generally the opposite. Obama administration policy is to support the existing dictatorship or at most to back a relatively cosmetic change in...