When Constantine died in 337 he left three sons to succeed him. All three were Christians. Constantine II took the west of the empire, Constantius the east, and the central provinces of Africa, Illyricum, and Italy went to the youngest, Constans. To secure their position they eliminated many of their close relatives but when, in 340, Constantine invaded Italy in the hope of adding it to his share he too was killed. Constans died in his turn in 350 after a successful coup by a usurper, Mag-nentius. The following year Constantius and Magnentius met in the great Battle of
Mursa (in today’s Croatia) where Magnentius was defeated but both armies suffered enormous losses. ‘Thus perished, wrote the historian Eutropius, ‘large forces that could have conquered any enemy and assured the security of the empire.’ After the battle the Alamanni who had been recruited by Constantius to help him went on the rampage in Gaul.
The truth was that the fundamental problems of the empire, the threats from outsiders from north and east and the instability of leadership, remained. Constantius ruled as sole emperor until his death in 361 and proved a conscientious ruler and commander but did not have the flair and charisma to galvanize the empire’s defence. For much of his reign he was preoccupied in the east where the Sasanian king Shapur II was energetically raiding into Mesopotamia. This meant that the northern borders of the empire were neglected and Gaul, in particular, was frequently ravaged. For the first time the Germans were able to take cities. The Gauls only enjoyed some respite when a young cousin of Constantius, Julian, nominated by him as Caesar and given the charge of Gaul in 355, surprised everyone by proving a highly effective commander. Both the Franks and the Alamanni suffered major defeats at his hands. By 360 order had been restored to the borders and Roman forces were stationed along them.
Constantius, still hard pressed in the east, now tried to remove some of Julian’s troops. They revolted and declared Julian an Augustus (360). Despite a half-hearted plea of loyalty to Constantius, Julian was ambitious enough to seize his chance and he was soon heading east. It was by coincidence that Constantius died before the rivals could meet in battle and Julian found himself sole emperor by default. Julian was the last of the pagan emperors and he attempted to re-establish the traditional cults of the empire (see below). However, he was only to survive eighteen months before dying at the hands of an unknown, but probably enemy, assailant in 363 while on retreat from an ill-judged campaign into Persian territory.
Julian’s successor was a Christian army officer, Jovian, who, caught in enemy territory, was forced into a humiliating surrender of border territory to the Sasanians. The advantageous position on the eastern frontier long held by the Romans was lost and this was a significant moment in the weakening of the empire. Jovian died on the way back to Constantinople. The army now chose Valentinian, a native of Pan-nonia, as the new emperor. Valentinian (emperor 364-75) was perhaps the last of the ‘great’ emperors. He was a tough man, often brutal, and completely intolerant of any challenges to his authority, but a fine soldier. He fought with success along the northern borders while at the same time quelling revolts in Britain and Africa. Archaeological evidence shows that he undertook a systematic programme of fort construction along the Rhine and Danube and on the main roads leading inland from the borders. For perhaps the last time the borders of the empire were effectively defended. Valentinian shared power with his inexperienced and much weaker brother Valens, whom he installed in the east of the empire.
The problems in assessing the size and competence of the Roman army in the fourth century are immense. There appears to have been a greater dependence on cavalry units and stronger defence installations on the frontiers but the overall size of the forces may not have been much larger than it was under Septimius Severus. If the number of laws relating to army service are an indication, there seems to have been difficulty in finding a flow of recruits ready to spend much of their adult lives away from their home communities. One trend was to recruit more troops from across the borders and this is attested by the increasing number of officers with Germanic rather than Roman names. How far these were truly committed to the maintenance of the empire is impossible to know but the strains were clearly beginning to show. The defeat of Valens by the Goths in 378 (see below) may not have been fatal but was symptomatic of an empire losing its cohesion. (See the discussions in chapter 5 of Simon James, Rome and the Sword, London, 2011, and David Potter, The Roman Empire at Bay, ad 180-395, Oxford and New York, 2004,448-59.)
World History
