- Decay,
- Vandals, and
- Religion, including Christianity.
Decay
The Roman Empire had become too big to control easily. Soldiers or families in distant parts of the Empire adopted local customs and the Empire was made up not only of natives from the Italian peninsula, but barbarians from the conquered lands. Corruption became rampant.Decay of the army, according to Vegetius (5th century), came from within the army itself, which grew weak from too long peace and stopped wearing its protective armor. This made them vulnerable to enemy weapons and to the temptation to flee from battle. Security may have led to cessation of the rigorous drills. Vegetius says the leaders became incompetent and rewards were unfairly distributed. See: "Vegetius on the Decay of the Roman Army, by Alfred P. Dorjahn and Lester K. Born. The Classical Journal, Vol. 30, No. 3 (Dec., 1934), pp. 148-158.
Historian Edward Gibbon on Decay and the fall of Rome"But the decline of Rome was the natural and inevitable effect of immoderate greatness. Prosperity ripened the principle of decay; the causes of destruction multiplied with the extent of conquest; and, as soon as time or accident had removed the artificial supports, the stupendous fabric yielded to the pressure of its own weight.... The victorious legions, who, in distant wars, acquired the vices of strangers and mercenaries, first oppressed the freedom of the republic, and afterwards violated the majesty of the purple. The emperors, anxious for their personal safety and the public peace, were reduced to the base expedient of corrupting the discipline which rendered them alike formidable to their sovereign and to the enemy; the vigour of the military government was relaxed, and finally dissolved, by the partial institutions of Constantine; and the Roman world was overwhelmed by a deluge of Barbarians."
- Gibbon - Decline and Fall of the Roman Empire
Christianity
When Constantine established religious toleration in the Roman Empire, he took upon himself the title of Pontiff. Although he was not necessarily a Christian himself (he wasn't baptized until he was on his deathbed), he gave Christians privileges and oversaw major Christian religious disputes. He may not have understood how the pagan cults, including those of the emperors, were at odds with the new monotheistic religion, but they were, and in time the old Roman religions lost out. Although the path from pagan to Christian Rome had a few more hurdles, it was from the time of Constantine that Roman Christianity is dated. At this early point, however, the emperors of Rome controlled the religion since emperors held the power to appoint bishops. Over time, Church leaders became influential and took away power from the emperor. Christian beliefs conflicted with the working of empire.
Christian Emperors, Persia, and The Fall of Rome
This is a chapter from Frank Smitha's "Antiquity Online" about the division of the Empire into East and West and the reign, including conversion of Constantine.
Vandals and Religious Controversy
Vandals took over the Roman territory in Africa, just as Rome lost Spain to the Sueves, Alans and Visigoths. A perfect example of how interconnected all the "causes" of Rome's fall are, Rome lost revenue along with the territory and administrative control. It needed revenue to support its army and it needed its army to keep what territory it still maintained. See: "The Decline of the Roman Power in Western Europe. Some Modern Explanations," by Norman H. Baynes. The Journal of Roman Studies, Vol. 33, Parts 1 and 2 (1943), pp. 29-35. Remnants of The Roman Empire
In this chapter from "Antiquity Online" -- about the 5th century Roman Empire, Frank Smitha shows the role of Vandals and religious controversies in the decline of Rome.
Among other points, Smitha says that Roman citizens living outside of Italy identified with Rome much less than their Italian counterparts. They preferred to live as natives, even if this meant poverty, which, in turn, meant they turned to those who could help -- Germans, brigands, Christians, etc.
Also see: The History of Florence, by Machiavelli.
Historian Edward Gibbon on the Fall of Rome and the Barbarians:"The warlike states of antiquity, Greece, Macedonia, and Rome, educated a race of soldiers; exercised their bodies, disciplined their courage, multiplied their forces by regular evolutions, and converted the iron which they possessed into strong and serviceable weapons. But this superiority insensibly declined with their laws and manners; and the feeble policy of Constantine and his successors armed and instructed, for the ruin of the empire, the rude valour of the Barbarian mercenaries."
- Gibbon
Rome and Roman Empire Maps
Economic reasons for the Fall of Rome
