In political terms, the changes can be best summed up as culminating a process of change from Republic to Principate to Dominate. The ideal of Roman society had always been a republic ruled by a senate that expressed the will of citizens by electing consuls whose tenures were limited. This was an ideal, in that only residents of Italy were counted as citizens, and equality was more between senators and consuls than among the populace as a whole. From the time of Julius Caesar (d. 44 BCE), however, the power of the individual leader had begun to increase in proportion to that of the Roman Senate. Ultimately, Octavian Augustus (r. 27 BCE-13 CE) established a Principate. Theoretically, the Princeps, or Emperor was close to being an equal to the Senate, or primus inter pares (first among equals). He and his successors for at least a century respected the Senate, reserved to it important fiscal, municipal, and appointive functions, and co-opted some of its members into the imperial bureaucracy as well as military roles. In truth, though, the power of the Princeps was beyond challenge, especially with the ascent of war-proven leaders at crucial times, such as Vespasian, Titus, Trajan, and Hadrian (69-120 CE). Still, almost every single emperor was of Italian origin or at least high-born and heavily schooled in Latin culture, and saw himself in such a perspective. The philosopher-king Marcus Aurelius was one of the last of these (r. 161-180 CE).

Contemporaneous with Aurelius, however, Barbarian incursions began along the Rhine and Danube. This opened the way for the ascent of a new kind of general and then emperor, which the Severi embodied. Increasingly non-Latin soldier emperors who proved their mettle on the battlefield, these Emperors have been called variously military emperors, camp-made, or barracks-room emperors. While these men were usually committed to pragmatic problem solving and maintenance of imperial frontiers, rapid and volatile imperial succession wreaked havoc on the Roman body politic. Further, as Balkan peasants, with partially barbarian backgrounds, it cannot be sure that they or their Balkan-German soldiers fully comprehended the Roman ideal they were protecting.

Problems of imperial continuity also point to the major 'Achilles heel' of Roman politics: imperial succession. Beyond hereditary rule, which was disconcerting to the Roman civic tradition, the Romans had never worked out a good system. Even in particularly problematic times though, such as the Year of the Four Emperors (68-69 CE), overall coherence of the imperial system, and persistence of local, senatorial, provincial administration had worked through the difficulties. Now, with foreign military pressures and their economic ramifications, political destabilization mattered much more. From 235-85, more than 20 plausible emperors were acclaimed by their armies. For the first time in generations, Pax-Romana cracked on the Rhine, in Gaul, and along the Danube.

Along with these changes in leadership dynamics were also economic changes, particularly in the provincial, agricultural sector. From the end of the first century, senators and other rural elites started to acquire large landholdings, farmed by hired labor. Called latifundia, these landholdings constituted a change from previously dominant small peasant landholdings in Gaul especially. Not only did this new arrangement cut down on the numbers of owners able to pay taxes, but latifundians often evaded tax obligations. In both cases, Barbarian incursions may have lessened capacity to pay. These changes in socio-economic relations meant that peasants could no longer be the tough citizen-soldier reservoir of the past. Also, aristocrats were no longer the best option for military leadership, since, assuming they were willing to leave their holdings, they could threaten insecure military emperors. Similarly, the town bourgeoisie had grown accustomed to peace and were not ideal soldiers. The military source of preference for the new emperors was either the Balkan peasantry they knew by blood ties, or Germans, to whom some third- century leaders were also connected by birth. Thus began the Germanization of the army proper, seeping eventually into the high command.

This turn of events was problematic, as Barbarian migrations of varying degrees of destructiveness were a dynamic lasting to the end of the Empire. Indeed, by the mid-third century, there was little ethnic difference between Roman armies and the Barbarian forces they fought. Further, continuous conflict, both in the West and against resurgent Persians under the Sassanids, meant that geographically wide-ranging military commitments outstripped military manpower, and sections of impossibly long borders were denuded of soldiers.

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