For two centuries following the death of Augustus (AD 14-235), the Mediterranean world experienced a singular period of peace and stability. Thereafter (AD 235-285), internal conflicts and foreign invasions overwhelmed and nearly destroyed the Empire. The purpose of this module is to illustrate the nature of the crisis and to describe at least some of its causes.

After a few missteps, Augustus organized and stabilized the Roman frontier. Subsequent Roman emperors made incremental additions on the periphery. Legionary camps, which were established along the Rhine and Danube and on the Syrian frontier, provided effective and steady defenses for the Empire. Population and productivity of the Roman Empire reached heights that would not be seen again until the Early Modern period. Moreover, the subject peoples of Europe began to "Romanize", acquiring the Latin language and the trappings of Roman urban culture. For the most part power passed peacefully from one emperor to another. Beyond the frontier, barbarian tribes also remained stable and quiescent.

By the mid 3rd Century, the Augustan system had broken down. Barbarian tribes penetrated the Empire at many points. Legions and their commanders became more interested in "emperor-making" than in "empire-defending". In these power struggles few emperors died a natural death. When the central government proved unable to defend the empire against both internal and external enemies, the provincials broke away and established their own regional imperial systems producing the Gallic Empire in the west and the kingdom of Palmyra in the East. Only after AD 285 did Diocletian and Constantine succeed in re-establishing a degree of order and stability. Though the Empire survived the crisis, it was transformed.

Section 1 examines border / defenses of the Empire from the death of Augustus (AD14) until the death of Severus Alexander (235).

Section 2 explores the nature of the turmoil during the 3rd century in more detail. In particular, the focus is on two issues; the growing barbarian pressures on Rome's frontier, and the increasingly chaotic imperial structure. These maps show the major barbarian incursions and note also the progressive abandonment of Roman frontier territory on the Rhine and Danube. They also show the fate of individual emperors from Septimius Severus to Diocletian, almost all of whom were killed by their own troops.

Section 3 explores graphically some factors (both internal and external) that fed the crisis. Finally, we offer a model that helps to explain the nature of the crisis.

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