Between 325 and 337 Constantine effected important reforms, continuing Diocletian’s work. The division between the limitanei border troops and the tactical troops (comitatenses and imperial guard) led by magistri militum was clarified, and military careers became independent of civil careers. At the same time, however, he lodged an increasing number of troops in or next to cities, a process whose objective was ease and economy of supply; however, training and discipline were harder to enforce because of it, and the men hung about in idleness. It was also under Constantine that a barbarian commander in the Roman army attained a historical significance. He was Crocus the Alaman, who led the movement among the troops that resulted in Constantine’s seizure of the rank of Augustus in 306 immediately after his father Constantius’ death. A similar figure was the great commander Bonitus, a Frank, in the years 316–324; and Constantine credited his victories against Maxentius in 311–312 principally to his barbarian troops, who were honoured on the triumphal Arch of Constantine in Rome. In opposition to him, Licinius mustered drafts of Goths to strengthen his army. Goths were also brought in by Constantine, to the number of 40,000, it is said, to help defend Constantinople in the latter part of his reign, and the palace guard was thenceforward composed mostly of Germans, from among whom a great many high army commands were filled. Dependence on immigrants or first-generation barbarians in war was to increase steadily, at a time when conventional Roman troops were losing military value.
Constantine raised many equestrians to senatorial rank, having in his earlier reign the still rapidly increasing ranks of the civil service to fill—it was at least 50 times the size of the civil service under Caracalla—and having in his later reign a second senate to fill, in Constantinople (see below). A rapid inflation in titles of honour also took place. As a result of these several changes, the equestrian order ceased to have meaning, and a new nobility of imperial service developed. Constantine gave first rank in the central administration to the palace quaestor, the magister officiorum, and the counts of finance (comes sacrarum largitionum, comes rei privatae). The diocesan vicars were made responsible to the praetorian prefects, whose number was increased and whose jurisdictions were now vast territories: the prefectures of Gaul, Italy, Illyricum, and the East. The unification of political power brought with it a corresponding decentralization of administration.
In order to reorganize finances and currency, Constantine minted two new coins: the silver miliarensis and, most importantly, the gold solidus, whose stability was to make it the Byzantine Empire’s basic currency. And by plundering Licinius’ treasury and despoiling the pagan temples, he was able to restore the finances of the state. Even so, he still had to create class taxes: the gleba for senators, and the chrysargyre, which was levied in gold and silver on merchants and craftsmen in the towns.
Constantine’s immortality, however, rests on his founding of Constantinople. This “New Rome,” established in 324 on the site of Byzantium and dedicated in 330, rapidly increased in population as a result of favours granted to immigrants. A large number of churches were also built there, even though former temples were not destroyed; and the city became the administrative capital of the empire, receiving a senate and proconsul. This choice of site was due not to religious considerations, as has been suggested, but rather to reasons that were both strategic (its proximity to the Danube and Euphrates frontiers) and economic (the importance of the straits and of the junction between the great continental road, which went from Boulogne to the Black Sea, and the eastern commercial routes, passing through Anatolia to Antioch and Alexandria). Constantine died on May 22, 337. The Roman Empire under the 4th-century successors of Constantine The rule of Constantine’s sons
After some months of confusion, Constantine’s three surviving sons (Crispus, the eldest son, had been executed in mysterious circumstances in 326), supported by the armies faithful to their father’s memory, divided the empire among themselves and had all the other members of their family killed. Constantine II kept the West, Constantius the East, and Constans, the youngest brother, received the central prefecture (Italy, Africa, and Illyricum). In 340 Constantine II tried to take this away from Constans but was killed. For the next 10 years there was peace between the two remaining brothers, and Constans won acceptance for a religious policy favourable to the Nicaeans, whose leader, Athanasius, had received a triumph in Alexandria. In 350 a mutiny broke out in Autun; Constans fled but was killed in Lugdunum by Magnentius, a usurper who was recognized in Gaul, Africa, and Italy. Constantius went out to engage Magnentius, and the Battle of Mursa (351) left the two strongest armies of the empire—those of Gaul and of the Danube—massacred, thus compromising the empire’s defense. Magnentius retreated after his defeat and finally committed suicide in 353.
Thenceforth, Constantius reigned alone as Augustus, aided by a meddlesome bureaucracy in which mission deputies (agentes in rebus), informers, and spies played an important role. He named two Caesars in succession, his two young surviving cousins, Gallus in the East and Julian in Gaul. Constantius eventually had to get rid of Gallus, who proved incompetent and cruel and soon terrorized Antioch. Julian, however, was a magnificent success, a fact that aroused Constantius’ jealousy and led to Julian’s usurpation; for the latter was proclaimed Augustus, in spite of Constantius’ opposition, at Lutetia in 361. Civil war was averted when Constantius died in November 361, leaving the empire to Julian, the last ruler of the Constantinian family.
At the time of his death in 337 Constantine had been preparing to go to war against the Persians. This legacy weighed heavily on the shoulders of Constantius, a military incompetent when compared to the energetic Sāsānian king Shāpūr II. Nearly every year the Persians attacked and pillaged Roman territory; the Mesopotamian towns were besieged, and Nisibis alone resisted. There was a lull between 350 and 357, while Shāpūr was detained by troubles in the eastern regions of his own kingdom. The war resumed, however, and Mesopotamia was partly lost when the emperor had to leave in order to fight Julian. Constantius had fought Shāpūr conscientiously, but his generals were mediocre, except for Urisicinus, and he himself was clumsy. In the meantime, the Rhine and Danube were threatened frequently, because the troops had been withdrawn from there and sent to the East. Constantius, moreover, had made a mistake in sending Chnodomar, the Alemannic king, against Magnentius in 351, for his tribes had gone on to ravage Gaul. Julian, however, soon revealed himself to be a great military leader by winning several well-fought campaigns between 356 and 361, most notably at Strasbourg in 357, and by restoring approximately 70 plundered villages. His abandonment, in 358, of the district of Toxandria, roughly equivalent to modern Belgium, to its barbarian squatters, on condition of their defending it against other invaders, was no doubt a realistic decision. Constantius defeated the Quadi and the Goths on the Danube in 359, but court intrigues, Magnentius’ usurpation, and the interminable war against the Persians allowed the barbarians to wreak great havoc.