Constantius II’s Sassanid War (337-350), [6/9]
Constantius’ strategy during this war was to build new forts and rely on the major fortress cities on the frontier such as Singara Iraq), Nisibis (Turkey) and Amida (Turkey) to hold up Persian incursions across Upper Mesopotamia.
In 338 Shapur II (70; r.309-379) invaded Mesopotamia, his cavalry swiftly overrunning the open country, burning crops and villages, slaughtering cattle and people. The great fortress of Nisibis, situated on the Mygdonius (=Jaghjagh) River and commanding the region, had to be taken but after a sixty-three day siege Shapur had to withdraw.
In 344 (or 348) a pitched battle (the only one of the war) was fought near Singara. The fighting began close to the Roman camp and the Persians withdrew as planned towards their own camp, which was some sixteen miles away; it being a favourite Persian tactic to use the heat of the day to tire the enemy before the main fight. When the battle neared the Persian camp the fresh Persian cataphracts (heavy infantry, resistant to arrows and edged weapons) were attacked by Roman infantry wielding clubs. On the unexpected defeat of their cavalry, the Persians broke and the Romans managed to capture the enemy camp. East of the camp the Persians rallied and their archers loosed an arrow storm into the camp causing many casualties, bringing an indecisive end to the battle.
In 346 Shapur laid siege to Nisibis for three months but failed to take the city. Four years later he dammed up the Mygdonius and managed to breach the wall by releasing the stored up water. The inhabitants, however, managed to refortify their wall before the Persian forces could enter the city.
Constantius II’s Civil War (350-353), [9/12]
In 340 Constantine II decided to wrest the control of Italy and Africa from Constans, which the former as the elder brother and senior augustus Constantine considered to be his by birthright. He crossed the Alps unopposed but near Aquileia in northeast Italy he was intercepted, defeated and killed by an advance guard sent by Constans from Naissus in Dacia, leaving Constans as the sole ruler of the Western Empire.
In 341/2 Constans drove back an inroad by the Franks and compelled them to conclude a peace; and in January 343 he crossed from Gesoriacum (=Boulogne) to Britain, perhaps to repel Picts and Scotii. However, he appears to have been unpopular with the army in 350 at Augustodunum (=Autun, France) the commander 26Flavius Magnus Magnentius (50; fl.350-353) was acclaimed augustus by his troops.
Constans fled for Spain and at the foot of the Pyrenees near the frontier fortress of Helenae (=Elne) he was murdered by Gaiso, an emissary of Magnentius. A month after Magnentius’ elevation he was joined by Italy followed by Africa soon afterwards. At about the same time, he appointed Magnus Decentius (probably his brother) as caesar in Gaul.
The Illyricum army was wavering but Vetranio, the magister peditum (‘master of the infantry’) on the Danube, allowed himself to be acclaimed augustus and then appealed to Constantius for help. The latter recognized Vetranio and ordered the troops on the Pannonian frontier to support him. Meanwhile in Rome, the elect of the mob, 25Flavius Julius Popilius Nepotianus, son of Constantine the Great’s half-sister Eutropia, enjoyed a brief and bloody reign of some twenty-eight days until he was killed by the soldiers of Magnentius.
In December 350 Constantius persuaded Vetranio to give up his claim to the throne and live out his life as a private citizen. In early 351 Constantius appointed his cousin 27Flavius Claudius Constantius Gallus caesar in the East and marched westwards to face Magnentius
In summer 351 Constantius’ army tried to force a way into Italy through the Julian Alps at Atrans (=Trojane, Slovenia), only to be repulsed. Magnentius attacked the city of Mursa (=Osijek, Croatia), but Constantius appeared and a battle took place on a flat open plain near the city. Using his superiority in heavy cavalry to crush Magnentius’ right flank, Constantius won a decisive victory, but only after an entire day of slaughter. Exhaustion and the approach of winter made pursuit impossible, and both sides had lost nearly thirty thousand men, an irreplaceable loss at a time when the Roman Empire was going to need every soldier it could find.
In 352 Constantius forced the passes of the Julian Alps, while his fleet dominated Sicily, Africa and the Po. Magnentius fled for Gaul and when Constantius’ forces followed too closely, Magnentius inflicted a meaningless defeat on them on the plains of Ticinum (=Pavia, northwest Italy). In 353 a battle at Mons Seleucus was fought which ended the usurpation. Magnentius fled to Lugdunum (=Lyon, France). where he committed suicide on 10 August. His caesar Decentius also perished by his own hand.
27Flavius Claudius Constantius Gallus, Constantius’ caesar in the East, crushed with great ferocity a revolt in Syria Palaestina in 352 and a civilian riot at Antioch late in 353, and quelled a rebellion in Isauria (central-south Asia Minor) in 354. Wrongly accused of treason, Gallus was executed by Constantius that year.
45Claudius Silvanus, a Frank who had deserted to Constantius before the Battle of Mursa, was appointed master of the infantry sent to Gaul to repel barbarian incursions. In 355 he was implicated in a political plot and to save his life he declared himself augustus at Cologne, but the revolt only lasted a few weeks and he was killed by his own soldiers.
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