Who Were the Successors of Constantine the Great?

On the 22nd of May in the year 337 CE, the Roman Emperor, Constantine the Great, passed away near the city of Nicomedia in northwestern Asia Minor. He had ruled as Emperor for thirty-one years, including thirteen as sole Augustus of the Roman state after periodically dismantling the tetrarchic order constructed under Diocletian. His passing saw the Roman Empire again split between multiple Augusti and his heirs quickly descend into internecine struggle. This article will explore the successors of Constantine the Great from his initial plans for succession, through to the death of his last surviving son.

Like his father before him, Constantine had set aside his first wife for a second, more politically astute choice. A year after his acclamation as Augustus by the legions in Britain, Constantine discarded his first wife, Minervina, for Fausta, daughter of the retired Augustus, Maximian. This helped solidify Constantine as a legitimate fellow in the tetrarch’s imperial college. However, also like his father, Constantine continued to see his son from his first marriage, Crispus, as his primary successor.

In 317 CE likely in his late teens, Crispus was elevated to the rank of Caesar in the west, anticipating his future succession to a higher rank. Alongside Crispus the son of the eastern Augustus, Licinius, and Constantine’s eldest son by Fausta, Constantine II, were also afforded the rank of Caesar.

Here we see Constantine beginning to stack the imperial deck of cards in favor of his blood relations. He would eventually remove Licinius in 324 CE and add the eastern provinces to his dominion. However, before that, Crispus took command in Gaul, basing himself at Trier and campaigning against the Franks and other Germanic tribes along the Rhine. In essence, beginning to secure a power base for himself among the Gallic legions.

Crispus must have felt fairly optimistic about his future career until 326 CE when he was suddenly executed on the orders of his father near modern Pula in Croatia. He was traveling to Rome with the royal entourage to celebrate the twentieth year of Constantine’s reign at the time. Shortly after Fausta also died, and though the manner of her demise could have been natural, it has also been rumored that Constantine had her suffocated in a steam room.

The motivations for or reasons behind Crispus and Fausta’s deaths remain a mystery, with several theories put forward. They range from the simple idea that Crispus was caught plotting to overthrow his father, to the accusation of a sordid affair between Crispus and Fausta, and also the belief that Fausta had framed Crispus to secure the future of her own sons in a post-Constantine power struggle. This would also potentially explain Fausta’s subsequent death after Constantine discovered her duplicity.

When Constantine died near Nicomedia, his middle son Constantius was on hand in the east to organize the funeral and receive the political acclaim associated with entombing his father in the center of the Church of the Holy Apostles in Constantinople (Eusebius, book 4.70). This was because, like his brothers and cousins, he had been elevated to the rank of Caesar sometime before his father’s death, and Constantius had been allocated authority over the East. Constantine’s nephew, Dalmatius, had been made Caesar in Macedonia and Thrace. His other nephew, Hannibalianus had been made a king of kings, ruling Pontus and Armenia and likely more if his uncle’s Persian campaign had succeeded. Constantine’s other two sons by Fausta — Constantine II and Constans — had been made Caesars in the west and Italy/Illyricum respectively.

Constantius was about to make the division of the empire slightly easier to understand. Shortly after his father’s funeral, Constantius locked down the palace in Constantinople and had the troops massacre his cousins and uncles including the aforementioned Dalmatius and Hannibalianus. This assured the division of the empire between Constantius and his two brothers. There did, however, remain two boys in the family, too young to pose any threat to Constantius at the time, Gallus and Julian.

The Neo-Triumvirate 

After Constantius had dispatched with most of his prominent male relatives in the slaughter at Constantinople, he traveled north to Sirmium. There he met his elder brother, Constantine II, and his younger brother Constans. Together they divided the Roman Empire between the three of them, however, Constantine II, the eldest brother, did not partake in the spoils of the massacre of the princes. Due to the locality of Dalmatius’s domains, Constantius and Constans divided his territories between themselves, with Constantius alone assuming Hannibalianus’s kingdoms. To massage the bruised ego of Constantine II he was given a sort of stewardship over his brother so that he felt he had authority over a portion of the empire befitting the eldest son of Constantine the Great.

The fact that the succession of the three sons was so disorganized, violent, and haphazard is because their father did not specifically plan who would succeed him and how. Constantine the Great had obviously intended his empire to pass to his sons and nephews as he had elevated them to prominent positions, but he never designated an official heir.

Generally, primogeniture, the inheritance by the eldest son, was practiced in the Roman world. However, Constantine’s bequeathal was more akin to the partible inheritance observed by Frankish kings in which the possessions of the father were divided between all the male heirs. Again, it is unknown why Constantine did not make any succession plans but several suggestions have been put forward. He may have feared an ambitious potential heir prematurely seizing power, like Crispus may have planned. He may have thought he had more time before he died, though at 65 he was no spring chicken. He may have intended for his sons to fight it out until the alpha of the pack achieved supremacy, as he had done over the other tetrarchs. Or, simply, he may have been too egotistical to care about anything after his own death.

The harmony between the three brothers did not, surprisingly, last long. Constantine II, obviously unsatisfied with his lot, began to covet the dominions of his youngest brother. First, he insisted that Constans hand over the African provinces, which Constans agreed to in the hope of avoiding conflict. However, he retained control of Carthage and its surroundings as he refused to break the valuable Carthage-Italy tax and grain spine.

In 340 CE Constantine marched into Italy in a ruse claiming to be marching to support his young brother’s campaigns in Dacia. However, he began to lay siege to Aquileia where he was killed by an elite detachment of Constans’s troops. From then on, the youngest brother took over the entire west and controlled the largest part of the empire.

The young Constans did not rule well. Sources describe his rule as an “intolerable tyranny” which led to much resentment from the noble and officer classes. He also rewarded a select body of Germanic troops with whom he hunted, to the neglect of the rest of the army. Gradually a conspiracy formed and in 350 CE the Rhine legions proclaimed the general Magnentius as emperor at a banquet in Autun. The rest of the western legions soon joined Magnentius’ cause and Constans, absent of support, chose flight. He was unable to escape Gaul before he was caught and executed.

Mursa Major

Magnentius had secured the support of the entire Gallic Prefecture, Britain, Gaul, and Hispania, and soon moved on to Italy. In Rome, one of the descendants of Constantine and a survivor of the massacre of the princes, Nepotianus, declared himself emperor. He lasted less than a month in the ancient capital before Magnentius’ forces paraded his head around the city. Meanwhile, in the Illyrian provinces, Constantina, daughter of Constantine the Great and sister to the remaining emperor, urged the old general Vetranio to proclaim himself emperor as well. Constantina must have feared that Magnentius was out to kill every member of the Constantinian family he could get his hands on and hoped that Vetranio could buy her some time while her brother was occupied in the east.

Constantius was already engaged in another round of the seemingly endless struggle with Sassanid Persia. After Constantine the Great’s sabre rattling, his death encouraged the Persian King of Kings to invade the Syrian provinces. Constantius had been dealing with this war intermittently ever since. However, this internal dissension could not go ignored so he began to wrap up operations in the east and march west with his legions. Vetranio and Magnentius initially presented a united front against Constantius, petitioning him to legitimize them as his junior colleagues. Constantius point blank refused to recognize Magnentius but accepted Vetranio as co-emperor for the time being. Once he reached Serdica in Illyria he deposed Vetranio, mercifully allowing him to live out his retirement, and united their forces to move against Magnentius.

The combined forces of east and west finally met in September 351 CE near the town of Mursa, in an eastern corner of modern Croatia. Though Constantius himself was busy praying, his generals and legions met Magnentius’ forces in a great battle that lasted well into the night. When dawn broke upwards of 50,000 men lay dead. Devastatingly for the prospects of the empire, these 50,000 dead were all Roman forces. This annihilation left the empire bereft of maybe between an eighth and a twelfth of its overall military strength. Constantius could claim victory, but nothing was decisive. He was not able to finally defeat Magnentius for another two years until the Battle of Mons Seleucus, 353 CE, after which the usurper ended his own life.

The death of Magnentius did not do much to ease the concerns of Constantius for the security of his throne. True, he was now the ruler of the whole empire, but the scope of his awesome power made him constantly worried about ceding or losing it. As he had left for the west for the campaign against Magnentius, he had appointed one of his surviving cousins, Gallus, as Caesar to rule over the east in his absence. Gallus proved either to be a decadent, ineffectual, and potentially treasonous Caesar, or he made enemies in Antioch that sought to portray him as such. Regardless, Gallus was eventually lured towards Milan in 354 CE with the promise of promotion to full Augustus. However, en route he was captured, interrogated, and executed by some of Constantius’ senior officers.

The fiasco with Gallus and the acquisition of the western portion of the empire must have made Constantius further realize how vast his domains truly were. A central administration would struggle to govern such a territory in the modern era, let alone with ancient bureaucracies and systems of communication. As a result, Constantius needed to delegate much of his power and implicitly trust his chosen representatives. He had massacred most of his male relatives and the one he had trusted, Gallus, had proved disastrous. He therefore chose a reliable Frankish general, Silvanus, to run the military establishment of most of the western empire. Using barbarian generals had become an unofficial imperial policy attempting to prevent powerful Romans from trying to claim the throne. However, Silvanus would prove that policy was ineffective.

Silvanus had been an important figure in the western military establishment for some time and had served under Magnentius. He had defected from the usurper to Constantius prior to the battle at Mursa, potentially impacting the result. He was rewarded with the position of Magister Militum (352 CE) for the Gallic provinces, a very powerful position due to the size of the army under his command.

However, Silvanus had enemies at the court of Constantius who doctored a letter to present evidence he was conspiring to seize the throne. Though the conspiracy was uncovered, the knowledge of Constantius’ paranoia pushed Silvanus into actual rebellion against the emperor in 355 CE. The revolt was short-lived and was put down in the same year, but it again convinced Constantius that he needed a strong familial connection in power in the west.

Here enters Julian. A fascination of contemporary and modern observers alike for his potential to impact on western history. He is usually given either the appellation “the philosopher” or “the apostate.” A nephew of the Great Constantine and the last remaining male relative of Constantius after the death of his cousin Gallus. Julian would have loved to have remained a scholar-cum-philosopher in the East but was removed from his studies to serve as Caesar in Gaul for his cousin. Here he won a victory against the Alamanni at the Battle of Strasbourg, in 357 CE and his successful generalship endeared him to his Gallic troops, who he promised he would never deploy in a foreign adventure.

Julian’s success in Gaul worried Constantius. He would be unable to deal with another western usurper as he was making preparations for an offensive against the Sassanids. In an attempt to kill two birds with one stone, in early 360 CE Constantius ordered Julian to send him half his legions to support the Persian campaign. Perhaps with some encouragement from Caesar, the western legions proclaimed Julian as Augustus in response. In 361 CE Julian began his march east while Constantius began his march west in anticipation of yet another confrontation between the forces of the two halves of the empire. However, en route, Constantius fell ill and died on the evening of the 3rd of November.

In his final hours, he named Julian as his sole successor and heir to the whole empire, preventing the continuation of civil war and keeping the imperial title within the family. Julian would face trials and tribulations of his own as the last emperor of the Constantinian dynasty, but with the death of Constantius II, we see the end of the rule of the sons of the Great Constantine. Constantius was entombed with his father in the Church of the Holy Apostles in Constantinople.