ORB Online Encyclopedia
Late Antiquity in the Mediterranean
The Collapse of the Roman Empire--Military Aspects
Modern historians explain the collapse of the western Roman empire in the fourth and fifth centuries in one of two ways. One group follows an institutional approach, which finds the reasons in the long-term and looks closely at internal structures. A second group has adopted a political approach and looks at short term causes of collapse.
The long-term approach is the more traditional of the two. This argument suggests that Diocletian (284-305) and Constantine I (305-337) sowed the seeds of collapse. These emperors split the army into border and mobile components. The border troops became soldier-farmers and declined rapidly in efficiency, though they were still paid. Diocletian and Constantine also allowed many barbarians into the army, which had the result of decreasing its fighting efficiency. These historians argue that the weakness of the border troops meant that emperors needed more mobile troops, so they expanded the army. This in turn increased the number of recruits needed, while a simultaneous reluctance of landowners to lose scarce workers led to the recruitment of the militarily inferior barbarians.
External problems exacerbated the internal crises of the empire. The small barbarian tribes who had opposed the early empire now banded together to form more powerful confederations such as Goths, Franks and Alamanni. However, some historians are doubtful about the increased power of these groups. Vigorous emperors like Diocletian, Constantine, Constantius II (337-361) and Valentinian I (364-375) kept the barbarians beyond the borders. Then the Huns arrived and drove the Goths into the Empire, defeating the army of Valens (364-378) at Adrianople in 378. From now on, the Romans could not destroy these Goths, although Theodosius I (379-395) finally settled them in the Balkans in 382. Once one group of barbarians had entered the Empire, the Romans could not muster the military strength to keep others out. Vandals, Alans and Suevi crossed the Rhine in 406 and barbarians went on to settle all over the western Empire. Visigoths, Alans and Suevi took land in Spain, Vandals in Africa and Burgundians, Visigoths and Franks in Gaul. Elsewhere, Saxons invaded Britain and at the end of the fifth century, Ostrogoths occupied Italy.
This is the traditional interpretation, with a stress on institutional weakness and the barbarian invasions. In various forms it has been followed by Theodore Mommsen, J.B. Bury, Andre Piganiol and Ramsay MacMullen. But others interpret the military events of this period differently, especially A.H.M. Jones, but also Averil Cameron and Hugh Elton. These historians stress that the Eastern empire did not fall when the West collapsed. Because of this, they doubt that internal institutional factors were the primary cause of the collapse. They are also unhappy with the idea of a two-century period of decline that lasted from Diocletian to the deposition of Romulus Augustulus in 476.
This second group of historians places the beginning of the end of the Roman Empire at various dates between 395 and 461 and their interpretations focus on the financial problems faced by the Empire. In the 395 division of the Empire, the West received fewer of the wealthy provinces. This in turn decreased the taxes collected. These commentators do not argue that the army was ineffective. Instead, they argue that paying for enough troops to fight was the problem. As well as facing diminishing resources, the West also had longer borders to defend. For these historians, western collapse was inevitable after 395, although the debate about when it could no longer be reversed is still important.
In this interpretation, the defeat of the eastern field army and Valens' death in Gothic hands at Adrianople in 378 is not a critical event. Although some historians stress this loss as the beginning of the end, since this allowed a group of barbarians into the Empire who were not expelled, others disagree. They point out that the Romans made no changes to the structure of their army after this battle. Far more important was the division of the empire in 395 between Arcadius and Honorius, the two sons of Theodosius, which robbed the Empire of strategic depth, with few transfers of money or troops between the two parts. The Vandals' invasion of Africa in 429, mostly completed by 439, had severe financial and strategic consequences. The loss of Africa not only removed the wealthiest provinces from western control but also exposed the Mediterranean (especially Italy and Greece) to pirate raids. A third critical event was the murder of Majorian (457-461) in 461, denying him the chance of recapturing Africa and holding the western empire together. After Majorian's murder, western Imperial unity finally dissolved. Aegidius in Gaul and Marcellinus in Dalmatia refused to accept the new emperor Libius Severus (461-465), raised to the purple by Majorian's murderer Ricimer.
A second important point to these commentators is the prevalence of civil war during the fourth and fifth centuries. The frequent occasions on which the Roman army was forced to fight itself caused a constant drain of resources, both financial and personnel, resources that might have been turned against external enemies. These wars included Constantine against Licinius (316, 324), Magnentius agianst Constantius II (351-353) and Theodosius against Magnus Maximus (383-388) and Eugenius (392-394). In the fifth century they spread to include Roman generals, e.g., Aetius against Bonifatius, although the usurpations of John (423-425) and Basiliscus (475-476) and Odoacer (476) were just as dangerous. Although civil war was a political problem, it had severe military effects, often provoking barbarian raids and weakening imperial ability to respond to them.
It is difficult to reach a conclusive verdict on why the western Roman empire fell. As these arguments show, it was a long and complex process, made more difficult to understand by the patchy nature of our evidence. If there was a simple answer, the Romans would surely have found it. Whatever the reasons, throughout the fifth century, when emperors could find money and assemble troops, the Roman army was a powerful and effective force. The institution itself was not at fault, but the support it received from its commanders-in-chief, the Emperors, was often lacking. If there was a single reason for the collapse of the western Empire, it was poor leadership, not military failure.
A Short Bibliography
Cameron, A., The Mediterranean World in Late Antiquity, AD 395-600 (London, 1993)
Elton, H.W., Warfare in Roman Europe: AD 350-425 (Oxford, 1996)
Jones, A.H.M., The Decline of the Ancient World (London, 1966)
MacMullen, R., Corruption and the Decline of Rome (New Haven, 1989)
Late Roman Army
"Barbarization" in the Late Roman Army
Late Antiquity Index
Copyright (C) 1996, Hugh Elton. This file may be copied on the condition that the entire contents, including the header and this copyright notice, remain intact.