The Arab Spring demonstrated the extent to which military structure and decision-making determine whether peaceful uprisings lead to democratization, renewed authoritarianism, collapse, or civil war. Other authors have attempted to address this question but most have been limited by the time and scope of their arguments. Many early arguments about military behavior misread the outcome in Syria, some focused on only three or four cases and thus missed key variables, and others focused so closely on the Arab Spring that they failed to account for the ways previous cases undermined their theories. Military behavior in the Arab Spring must be explained on its own, but the Arab Spring also provides an opportunity for broader theorizing about military response to popular uprisings and demands for democracy. The militaries in the Arab Spring were more diverse in structure and behavior than in previous regional waves of uprising, like Eastern Europe in 1989, Sub-Saharan Africa in the 1990s, or Latin America in the 1980s. As such, the events provide a fertile ground for building larger theories about the military in democratization while addressing the specifics of the Arab Spring cases. Based on research from the author’s upcoming book, "Revolts and the Military in the Arab Spring," to be published in 2018 by IB Tauris, this paper looks at seven popular uprisings, six Arab Spring cases and the 1977-1980 Iranian Revolution, and shows the key role military structure plays in regime survival and regime transformation. Using the civil-military relations and coup-proofing literature, the author breaks down the key facets of military structure into seven characteristics. He uses those variables to measure two key features of military structure: distance from the regime and internal cohesion. He then shows how different configurations of these features lead to military coup, successful repression, collapse, or civil war. In cases of regime collapse, other military structure variables are used to predict whether the outcome of the transition will be democratization, utopian revolution, or renewed authoritarianism. Unlike many studies of military behavior in the Arab Spring, the paper uses variables and methodology that are transportable other regions and time periods, building on both the Middle East literature and the democratization literature. As such, it provides both a better explanation for military behavior than other, more narrowly drawn, explanations of the Arab Spring, as well as using the Arab Spring to make broader observations about military structure and democratization.