Flavius Julius Constantius (August 7, 317 – November 3, 361), commonly known as Constantius II, was Roman Emperor from 337 to 361. The second son of Constantine I and Fausta, he ascended to the throne with his brothers Constantine II and Constans upon their father's death. In 340, Constantius' brothers fought over the western provinces of the empire. Constans defeated his brother and ruled the west for a decade until the usurper Magnentius rebelled in 350. Constans was promptly assassinated, leaving Constantius as the only surviving son of Constantine. After defeating Magnentius at the battles of Mursa Major and Mons Seleucus, the usurpers subsequent suicide left Constantius sole ruler of the empire. His military campaigns against Germanic tribes were successful: he defeated the Alamanni in 354, and campaigned across the Danube against the Quadi and Sarmatians in 357. In the east however, he fought the Sassanids for two decades with mixed success. Constantius elevated his cousin Julianto co-emperor in 355, but by spring 361 the two emperors were at war. However, Constantius died before the two could face each other in battle, naming Julian his successor.
Early life
Division of the Roman Empire among the Caesars appointed by Constantine I: from left to right, the territories of Constantine II,Constans I, Dalmatius and Constantius II. After the death of Constantine I (May 337), this was the formal division of the Empire, until Dalmatius was killed and his territory divided between Constans and Constantius. Constantius was born in 317 at Sirmium, Pannonia. He was the third son of Constantine the Great, and second by his second wife Fausta, the daughter ofMaximian. Constantius was made Caesar by his father on 13 November 324.
When his father died at Constantinople on 22 May 337, Constantius was the nearest of his sons to that city. Despite being on campaign in the eastern provinces, he immediately returned to the city to oversee his father's funeral.
The role of Constantius in the massacre of his relatives descended from the second marriage of his paternal grandfather Constantius Chlorus and Theodora) is unclear. Eutropius, writing between 350 and 370, writes that Constantius merely sanctioned “the act, rather than commanding it”. However, it should be noted that Eutropius was hostile to Constantius - he was a friend of Julian - Constantius’ cousin and ultimately his enemy. Constantius, his older brother Constantine II, his younger brother Constans, and three cousins Gallus, Julian and Nepotianus were left as the only surviving male relatives of Constantine the Great.
Meeting at Sirmium not long after the massacre, the three brothers proceeded to divide the Roman Empire among them, according to their father's will. Constantius received the eastern provinces, including Egypt, Syria, Thrace, and Asia Minor. Constantine II received Britannia, Gaul, Hispania, and Mauretania. Constans, though initially under the supervision of Constantine II, received Italy, Africa, Illyricum, Pannonia, Macedonia, and Achaea.
Reign in the East
Missorium of Kerch depicting Constantius II on horseback with a spear. He is preceded by victory and accompanied by a guardsman. There are few details of the early years of Constantius' sole reign in the eastern provinces. He spent most of his time defending the eastern border against invasions by the aggressive Sassanid Empire under king Shapur II. These conflicts were mainly limited to Sassanid sieges of the major fortresses of Roman Mesopotamia, including Nisibis, Singara, and Amida. The Sassanids were able to achieve little, though Shapur seems to have been victorious in most of theconfrontations. However, the Romans won a decisive victory at the Battle of Narasara, killing Shapur's brother Narses. Ultimately, Constantius was able to push back the invasion, Shapur failing to make any significant gains. Meanwhile, his brother Constantine desired to retain control of Constans' realm - leading Constantius' two brothers into open conflict. Constantine was killed in 340 near Aquileia during an ambush, As a result, Constans took control of his deceased brother’s realms and became sole ruler of the Western two-thirds of the empire. This division lasted until 350, when Constans was assassinated by forces loyal to the usurper Magnentius.
Constantius spent much of the rest of 353 and early 354 on campaign against the Alamanni on the Danube frontier. The campaign was successful and raiding by the Alamanni ceased temporarily. In the meantime, Constantius had been receiving some disturbing reports regarding the actions of his cousin Gallus. Possibly as a result of these reports, Constantius concluded a peace with the Alamanni, and traveled to Mediolanum.
In Poetovio, Gallus was arrested by the soldiers of Constantius under the command of Barbatio. He was then moved to Pola, and interrogated. Once there, Gallus claimed that it was Constantina who was to blame for all the trouble that had been caused while he was in charge of the eastern provinces. At first, this so greatly angered Constantius that he immediately ordered Gallus' execution. Soon after however, he changed his mind and recanted his order. Unfortunately for Gallus, this order was delayed by Eusebius, one of Constantius‘ eunuchs, and as a result Gallus was executed.Once there, he decided to first call Ursicinus, Gallus’ magister equitum, to Mediolanum for reasons that remain unclear. Constantius then requested the presence of Gallus and Constantina. Although at first Gallus and Constantina complied with the order, when Constantina died in Bithynia, Gallus began to hesitate. However, after some convincing by one of Constantius’ agents, Gallus continued his journey west, passing through Constantinople and Thrace to Poetovio in Pannonia.
More usurpers and Julian
On 11 August 355, the magister militum Claudius Silvanus revolted in Gaul. Silvanus had surrendered to Constantius after the battle of Mursa Major. Constantius had made him magister militum in 353, with the purpose of blocking the German threats, a feat that Silvanus achieved by bribing the German tribes with the money he had collected. A plot organized by members of Constantius' court led the emperor to recall Silvanus. After Silvanus revolted, he received a letter by Constantius that recalled him to Milan, but which made no reference to the revolt. Ursicinus, who was meant to replace Silvanus, bribed some troops, and Silvanus was killed.
However, Constantius realised that too many threats still faced the Empire, and he could not possibly handle all of them by himself, so on 6 November 355, he elevated his last remaining relative, Julian, to the rank of Caesar. A few days later, Julian was married to Helena, the last surviving sister of Constantius. Not long after Constantius sent Julian off to Gaul.
Constantius spent the next few years overseeing affairs in the western part of the empire primarily from his base at Milan. In 357 he visited Rome for the first and only time in his life. The same year he forced Sarmatian and Quadi invaders out of Pannonia and Moesia Inferior, then subsequently led a successful counter-attack across the Danube against the enemy.
In the winter of 357-8, Constantius received ambassadors from Shapur II who demanded that Rome restore the lands surrendered by Narseh. Despite rejecting these terms, Constantius still tried to avert war with the Sassanid Empire by sending two embassies to Shapur II. As a result of Constantius' rejection of his terms, Shapur II launched another invasion of Roman Mesopotamia. In 360 when news reached Constantius that Shapur II had destroyed Singara, and taken Kiphas, Amida, and Ad Tigris, he decided to travel east to face the re-emergent threat.
Usurpation of Julian and crises in the east
In the meantime, Julian had won some victories against the Alemanni tribe, who had once again invaded Roman Gaul. As such, Constantius requested reinforcements from Julian for his own campaign against Shapur II. However, when he requested reinforcements from Julian’s army, the Gallic legions revolted and proclaimed Julian Augustus.
However, on account of the immediate Sassanid threat, Constantius was unable to directly respond to his cousin’s usurpation other than by sending missives by which he tried to convince Julian to resign the title of Augustus and be satisfied with that of Caesar. By 361, Constantius saw no alternative but to face the usurper with force; and yet the threat of the Sassanids remained. Constantius had already spent part of early 361 unsuccessfully attempting to re-take the fortress of Ad Tigris. After a time he had withdrawn to Antioch to regroup and prepare for a confrontation with Shapur II. However, the campaigns of the previous year had inflicted heavy losses on the Sassanids and they did not attempt another round of campaigns that year. This temporary respite in hostilities allowed Constantius to turn his full attention to facing Julian.
Death
Constantius immediately gathered his forces and set off west. However, by the time he reached Mopsuestia in Cilicia, it was clear that he was fatally ill and would not survive to face Julian. Apparently, realising his death was near, Constantius had himself baptised by Euzoius, the Semi-Arian bishop of Antioch, and then declared that Julian was his rightful successor. Constantius II died of fever on 3 November 361.
