Constantine the Great, emperor of the Western Roman Empire (c. 312-324), and later the entire Roman Empire (c. 324-337), climbed to ultimate power after defeating a host of rivals in a long and bloody civil war. Despite experiencing firsthand the complications that come with dividing a single empire among multiple emperors, Constantine the Great groomed all three of his legitimate sons for rule and gave them each the title of caesar. When Constantine the Great died in 337, none of his sons were given primacy. All three of them, Constantine II, Constans I, and Constantius II all proclaimed themselves to be an augustus (or emperor), and divided the empire amongst themselves. Constantine II ruled Roman Britain, Gaul (France) and Spain. Constans I took Italy, North Africa (excluding Egypt) and some of the Balkans. Constantius II took the remainder of the Balkans, and the rest of the Roman lands, with land spanning around the Mediterranean from Greece to Egypt.
Although the empire fell in succession to Constantine’s sons, it was these sons, and these sons only, who controlled the Roman Empire—all other relatives were considered a threat. In a plan probably masterminded by Constantius II, the emperors purged the land of potential rivals, including many of their own cousins and even a half-brother of Constantine the Great, ironically also named Constantius. Two notable imperial cousins that survived the purge were Gallus and Julian, the former would be a future caesar and the latter a future emperor.
The three emperors managed to coexist for a few years, but border friction and the competing ambitions of the brothers made war inevitable. In 340, Constantine II invaded Italy, hoping to seize the old heart of Rome from his brother. Yet, his plan backfired—Constantine II died in an ambush set by Constans’ men in Aquileia that very year. Although Constantine II had initiated the war, it was Constans who became master of the Western Roman Empire.
Meanwhile, Emperor Constantius II was fighting the Sassanian King Shapur of Persia. The war between the two began around 338 and would last, with only a few short intermissions, for the duration of Constantius’ reign.
The intermission came in the 350s, when rebellions broke out and various tribes started threatening Roman territory near the Danube River. In the year 350, a rebel named Magnentius captured and executed Emperor Constans, claiming much of Europe as his own. Another opportunistic rebel named Vetranio also seized a portion of land in the western Balkans.
Constantius II, now the sole emperor of the Roman Empire, promoted Gallus (one of the cousins that survived the purge) to the position of caesar, and left him to manage the east, and keep an eye on the Persians, while the emperor took care of the rebels. In an impressive display, Constantius II managed to pacify both Vetranio and Magnentius as quickly as 351.
While Constantius II was crushing the rebellions, Gallus was doing his job in the east. Yet, although he had the military skill for his position as caesar, he failed to gain the affection of his men. By 354, Emperor Constantius II lost faith in his caesar, and had Gallus executed on the charge of treason. The following year, in 355, the emperor appointed Gallus’ brother, Julian, as the new caesar.
The emperor and his caesar quickly went to work fighting the enemies of Rome. In central Europe, Julian won victories against the Alemanni and the Franks. In 357 or 358, Constantius II also fought against threats along the Danube, including the Sarmatians, Suebi and Quadi. Yet, as soon as that was accomplished, Constatius II eagerly returned to fight his true rival, King Shapur II of Persia.
Constantius II’s downfall came around 360, when he demanded that Julian send his most veteran troops to fight in the eastern front. While it may seem like a reasonable request, both Emperor Constantius II and the caesar knew that compliance would leave Julian in a vulnerable position, especially in Roman politics. Therefore, Julian refused the request and was proclaimed emperor by his soldiers. Understandably, Constantius II took the rebellion of Julian badly. As he was marching home to face his cousin, Emperor Constantius II grew ill, or suffered an embolism, and died in 361, leaving the Roman Empire to Julian.
Top picture attribution: (Collage of Constantine (front), Constantius II (left), Constantine II (middle) and Constans (right), via Creative Commons (CC2.5), pixabay.com and the Classical Numismatic Group, Inc.)
Written by C. Keith Hansley.
- The Byzantine Art of War by Michael J. Decker. Pennsylvania: Westholme Publishing, 2013.