A wide-ranging historical narrative traces the late imperial period through successive crises of succession, civil war, and administrative strain, showing how unclear rules of legitimacy and the army's intervention undermined central authority. The author analyzes fiscal retrenchment, popular reactions to austerity, and the rivalry between senatorial ideals and military power, linking political turbulence to moral and institutional decay. Chapters combine close political narrative with reflections on cultural shifts, including the adoption of nonhereditary succession practices, and conclude by mapping how internal divisions and changing traditions eroded the old frameworks of Roman governance.