Been listening to and relistening to Mike Duncan’s “The History of Rome”. One thing that seems agreed upon in the literature is that one of the main reasons the West fell is because the super-rich landowning classes withheld money, manpower, and political support from the army more and more throughout the 5th century. One of the main reasons for this as far as I can tell is that the senatorial class — which to my mind is basically synonymous with “wealthy landowning elites” — were barred from serving in senior positions in the military from the reign of Gallienus on. This seems like it completely divorced the elites from the needs and realities of the military over time, leading, in part, to the complete degradation of the West’s military.
I understand this question is kind of predicated on that causal inference being correct — but why was this division kept (If it was indeed kept until at least the fall of the West)? Romans always seemed so concerned about becoming effete and detached from their martial traditions so why wasn’t this reversed
Thank you!
The short answer is that the division of responsibility was implemented to prevent politics rivals from acquiring too much power. To understand the split, you must first understand the 3rd century political and military environment that Gallienus inherited from his father.
The Roman Empire functioned at its best when the Emperor, Senate, Praetorians, and Army controlled proportional amounts of power. Beginning with Septimius Severus’s reign in 193, this power balance broke down. Septimius ruled effectively, but his policies did serious long term damage to the political framework of the Empire. Namely, he increased the number of legions from 30 to 33 and significantly increased the soldiers’ pay. He also largely ignored the Senate as a policy. His son and successor, Caracalla, continued these policies and further increased soldiers’ pay.
Such exorbitant pay had several negative effects. First, it created an unstable financial burden for the Roman state. Second, it elevated the Army’s sense of value. Third, the Roman emperors tried to resolve the issue by debasing the currency without success. Instead of stabilizing the situation, runaway inflation exacerbated the empire’s problems.
Meanwhile, the Army had played a role making emperors in the past, as they had elevated governors during succession crises following the deaths of Nero and Commodus. In The Crisis of the Third Century, as we know it, the army abused this power and wielded it carelessly. From 250-290 ce, the Pannonia & Moesian legions elevate four successive emperors to the purple. Whenever a potential successor appeased them more than the current emperor, the army happily elevated him to the purple.
With so much internal strife, emperors were unable to defend the borders, were fighting off usurpers, and struggling to maintain the bureaucracy. Simply put, running the empire was too large a task for one man to handle.
In an effort to stabilize the situation, Emperors made the conscious decision to remove potential rivals. The Senate was largely irrelevant at this point, so removing the military career path removed them completely as political rivals. This was not a decision that considered long term localization, but a reaction to chronic political instability.
TLDR; the decision to bar Senators from military positions was largely an effort to stabilize the political mess in the Third Century.