The 2011 uprisings in the Arab world shared similar characteristics and produced radically divergent outcomes. The tens of thousands of protesters who took to the streets in Tunisia, Libya, Egypt, Yemen, Bahrain, and Syria clamored nonviolently for regime change. The urban poor, Westernized elite, Islamists, union activists, liberals, and leftists mobilized along cross-class, cross-regional, and nonpartisan lines. The commonalities in terms of motivations, grievances, protest size, as well as the peaceful nature of the popular mobilization, were unmistakable. And yet the popular movements triggered markedly different military responses. In Syria and Bahrain, the armed forces sanctioned bloodbaths to defend their leaders. In contrast, the military refrained from using violence in Egypt and Tunisia. Meanwhile, troops splintered in Libya and Yemen where some units defected wholesale whereas others stayed loyal and willing to uphold autocracy.