Magnentius As Emperor
Aurelius Victor says that Magnentius' brother, Flavius Magnus Decentius,
was raised to the rank of Caesar prior to the rebellion of Nepotian because Magnentius
suspected there would be trouble in some part of his empire (De Caes. 42). Zonarus
places this event at Milan during June 350 (13.8.5-13). Decentius was given the task of
protecting the provinces beyond the Alps but, initially, his role probably would have been
to assist his brother should rebellion break out (Zos. 2.45.2). Generally, it is
accepted that Decentius' elevation came in July or August in reaction to Nepotian.  The
usual time given for Decentius' elevation is March 351, at the same time Gallus was made
Caesar by Constrantius. This date seems to square with Decentius' consulship (held in
352). However, even if Decentius was named Caesar in 350 he would have waited for his
consulship since Magnentius and Gaiso had already been named to fill the offices for 351.
Numismatic evidence exists that bears on Decentius' elevation. The GLORIA
ROMANORVM reverse type was in use by Magnentius prior to Nepotian's rebellion and was
gradually replaced at the Rome mint with the RENOBATIO VRBIS ROME and VRBS ROMA types.
GLORIA ROMANORVM is not usually associated with Decentius, as it was in use prior to his
presumed elevation. However, there are examples that were struck in Rome for Decentius,
which would confirm an earlier date for his new rank.  Another issue by the Rome
mint for Decentius was the RENOBATIO VRBIS ROME type with MAG DECENTIVS.N.CS (using a
solidus die) as the obverse legend, which supports a summer 350 elevation. Perhaps
Decentius had gone to Rome following the death of Nepotian to assess the loyalty of the
city and assumed the rank of Caesar there. 
Around the same time, Magnentius married Justina, who is thought to have
been a daughter of Justus, a praetorian prefect of Licinius and consul in 328, who married
a daughter of Crispus Caesar (Socrates H.E. 4.31.11-13). This gave Magnentius a
family connection to Constantius since his wife was a great-granddaughter of Constantine.
Following the fall of Magnentius, Justina married Valentinian I, bearing him four children
and becoming a powerful figure during the reign of her son Valentinian II.
Magnentius' policies and propaganda reflect his position as a usurper and
that he replaced a corrupt and incompetent regime. He was proclaimed as the
"liberator of the Roman world", the "restorer of liberty and the
state" and the "preserver of the soldiers and provincials" (ILS 742). He
sought potential allies wherever he could. Overtures were made to Paul, bishop of
Constantinople who, like Athanasius, was condemned for his Orthodox Christian beliefs. An
embassy sent by Magnentius to Paul placed the bishop in a dangerous position; he was
imprisoned, starved for six days and strangled on the orders of Philippus, Constantius'
Athanasius was approached by an embassy consisting of two Gallic bishops
and two unidentified men, escorted by two military men named Valens and Clemertus. They
came to Alexandria, by way of Libya, pretending to represent Constantius (Apol. Ad
Const. 9-10). Magnentius may have been hoping he could detach Egypt from Constantius
if Athanasius would support him. According to Athanasius' account, the envoys brought no
letter from Magnentius and he repulsed the efforts of the men to enlist his aid.
Nonetheless, the bishop was accused of writing to Magnentius, which he denied saying that
a letter produced by his enemies was a forgery. This accusation, along with some standing
charges, was later used to remove the bishop. But was the letter a forgery? Magnentius had
reason to believe Athanasius might welcome his support. Constantius had selected George of
Cappodocia to replace Athanasius as bishop of Alexandria, and had sent Philippus to arrest
the bishop when news of the death of Constans arrived. Constantius saw the potential
danger Athanasius could become and wisely withdrew his plan, denying he wished to remove
the bishop, until after Magnentius had been defeated (Hist. Ar. 51.4).
Constans, following the laws initiated by his father in the East, had
prohibited pagan sacrifices and probably seized temple treasure late in his reign.
Magnentius overturned the prohibition. An inscription by a priest tells us that after
twenty-eight years he was able to make "the offering of his actions, his intelligence
and his life" by being able to lead a bull and ram to sacrifice to the Great Mother.
 Following the defeat of his rival, Constantius ordered that the "nocturnal
sacrifices allowed under Magnentius' authority" be abolished (C.Th. 16.10.5).
The favor that Magnentius showed to pagans has been construed to mean the emperor was
pagan himself. Philostorgius seems to suggest Magnentius was pagan when he says the
emperor was addicted to superstitious practices (3.26). However, Athanasius says
Magnentius was baptized (Apol. Ad Const. 241.7) but is the only source suggesting
the emperor was a Christian.
The army was recruited from young men living in the rural countryside
where Christianity had made no inroads. Constantine was concerned with maintaining the
loyalty of his army and so made no attempt to convert the soldiers to Christianity. At
Julian's time, the army had remained largely pagan. Soldiers treated their differences in
religion with toleration. Had Julian's religious faith been a problem, why, upon his
death, did the senior commanders select another pagan, Secundus Salutius, as the new
emperor? Only after Salutius refused (because of his age) was the Christian Jovian
selected (Amm. 25.5.1). Action against pagans did not begin until after Magnentius'
defeat when Constantius, who was not loath to welcome the services of eminent pagans,
closed all temples and prohibited sacrifices under pain of death. 
It is impossible to be certain what faith Magnentius practiced. However,
he had to exercise the same constraint as Constantine with regard to his army so as not to
offend Christians or pagans. The overturning of Constans' prohibition of pagan sacrifices
may have stemmed from a need to appeal for pagan support. If Magnentius acted from his own
beliefs, we have no way of being certain.
Following the abdication of Vetranio, Constantius probably resided at
Sirmium where he carefully sized up the military situation. Battling Magnentius would keep
him away from critical situations in the East for many months. To ensure stability, the
presence of a member of the imperial family was needed. Constantius was childless, the
consequences, he thought, for the murder of his uncles and their families. Putting aside
his suspicions, he brought his cousin Gallus out of exile to represent the House of
Constantine in his place (De Caes. 42; Zos. 2.45; Philostorg.
3.27,28; Amm. 14.1.1).
Gallus had been spared during the dynastic blood bath because of his age
(eleven or twelve) and ill health. He was first entrusted to the care of Eusebius, bishop
of Constantinople, then was sent to Macellum, a remote imperial estate in Cappodocia.
There, Gallus and his half-brother Julian were put under the spiritual care of George of
Cappodocia, who eventually replaced Athanasius as bishop of Alexandria. Gallus was
summoned to court and created Caesar on March 1, 351. He was married to Constantia and
sent to Antioch, not to administer the East but to be Caesar in name only.
The Battle of Mursa
During the winter of 351, Magnentius closed the passes through the Julian
Alps into Italy. He had made a triumphal entry into Aquileia, possibly in January, and
would use the city as his base of operations. In the spring, Constantius tried to break
through into Italy but was repulsed at Altrans. Magnentius sought to pursue his advantage
and marched into Pannonia Superior, occupying Siscia by the summer (Zos. 2.46.1).
Constantius sent Philippus on the pretense of negotiating a truce but, in reality, to spy
on Magnentius. At a meeting with Magnentius, the prefect expressed dismay that Romans
would be killing each other and reminded the emperor that Constantine I and his sons had
been kind to him and his family, granting Magnentius high honors. He concluded by
suggesting Magnentius withdraw from Italy and be content to rule the provinces north of
the Alps (Zos. 2.46.2-3; Zonarus (13.8) says the offer was made in a letter, which
Magnentius arrogantly refused).
According to Zosimus (2.47.1), the offer almost drove the army to mutiny,
terrifying Magnentius. The next day, however, Magnentius harangued his soldiers, reminding
them of how Constans had mistreated them and how they had sought to free themselves from
an oppressive regime. His troops rallied to him, giving Magnentius the courage to continue
with his conquest of the entire empire. Magnentius sent a counter offer to Constantius
with a senator named Titianus. The message was a penetrating indictment of Constantine and
his sons and ended by telling Constantius to stand down. This tactless insult allowed
Constantius, with righteous indignation, to declare that he would avenge the murder of his
brother (Zos. 2.48-49). 
Although Zosimus says that Magnentius took Siscia and raised the city,
ransacking the area for booty, it is meant only as a comment on his "barbarous
nature" (2.49.2 ). The emperor took over the imperial mint and briefly issued coins
from Siscia wishing to make allies not enemies. Magnentius did not linger at Siscia and
continued his march to Sirmium. There, he failed to capture the city when met with token
resistance. Resuming his march, Magnentius laid siege to the city of Mursa where his
forces were kept at bay by stiff resistance from the citizens. Hoping to quickly end the
siege, Magnentius ordered the wooden city gate to be set afire only to watch the citizens
douse the flames with water (Zos. 2.49.3-4). Constantius, who had earlier pulled
his forces back to Cibalis, marched to relieve the city. Magnentius, learning of
Constantius' approach, set an ambush by luring the latter's troops (hoping the emperor
would be among them) to a stadium overgrown with trees. The plan failed and Magnentius'
troops were overwhelmed and killed to a man (Zos. 2.50).
On September 28, 351, the armies met on a plain outside of Mursa.
Constantius positioned his forces with the Drava River to his right and the Danube to his
back; his soldiers were given little choice but to win or be annihilated (Or. 1
35D). His Persian styled cavalry was grouped in both wings with archers; heavy infantry
occupied the center with additional archers and slingers in the rear (Or. 1 36A).
Just before the battle, the tribune Silvanus deserted Magnentius with his cavalry for
Constantius, perhaps the consequences of the provocative speech by Philippus. 
Battle was joined in late afternoon and fighting was fierce on both sides. Julian
says Constantius' left outflanked Magnentius and his phalanx was overwhelmed. Eventually,
it was Constantius' mail-clad cavalry that made the difference (Or. 1 37A); they
overwhelmed Magnentius' right and threw the entire line into confusion. Magnentius was
almost captured (Eutrop. 10.12 ) and fled the battlefield. But the Gauls refused to
surrender and fought on with Marcellinus, who was killed (Or. 2 58D). The soldiers
on both sides were so enraged that they continued to fight even after night had fallen (Zos.
2.51.2-3). Julian blamed Magnentius for his own defeat saying he was guilty of gross
incompetence in that he did not know how to position his phalanx. He also accused him of
cowardice by fleeing the battlefield to leave others to carry on the fight (Or. 1
Magnentius was forced to withdraw but Constantius was not able to take
advantage of his opponent's weakness. This was a Pyrrhic victory. As many as 54,000 dead
(Magnentius' dead were put at 24,000 and Constantius' at 30,000) lay on the field making
this the bloodiest of all Roman battles. The Roman army was weakened beyond repair at a
time when every man was needed to guard the frontiers against threats from barbarian
tribes. Constantius had at his disposal 80,000 soldiers as compared to Magnentius' 36,000
(Zon.13.8.5-13; De Caes. 42.9-10; Zos. 2.46.2 ). If these figures can
be taken as fact, then Magnentius suffered casualties amounting to two-thirds of his army.
The reason for the smaller number of forces available to Magnentius (who at one time had
superior numbers (Zos. 2.45.2)) can be explained by his leaving a force at Sirmium
to lay siege to the city rather than casually bypass it. If true, by splitting his forces,
Magnentius made a fatal blunder that Constantius quickly turned to his advantage.
A Last Stand
Magnentius retreated to Aquileia, blocking the passes through the Julian
Alps. Winter ended the campaign season but Constantius had shown no inclination to pursue
Magnentius. Instead, he offered amnesty to any of Magnentius' followers who surrendered,
except for those who were directly involved with his brother's murder. This caused many
desertions from Magnentius' ranks (Or. 1 38B; Zon. 13.8.23). Magnentius
renewed his offer to negotiate, but it was refused. Constantius sent letters to the
barbarian tribes living along the Rhine with large donatives to encourage them to attack
Magnentius (Zos. 2.53.3; Libanius 18.33-34). The barbarians were only too
happy to invade Gaul, thereby keeping Decentius busy and removing much-needed troops from
his brother's forces. This plan had an unfortunate aspect in that the barbarians
devastated Gaul, destroying crops and causing towns and villages to be deserted.
Magnentius has been accused of plotting to have Constantius Gallus
murdered to force Constantius to return to the East. The plot is related by Zonarus, a
Byzantine military commander turned monk (13.8.24-26), and involves a servant of
Magnentius who is chosen to murder the Caesar. The assassin lodged with an old woman who
lived near the Orontes River at Antioch. He became a friend of several disaffected
soldiers, who agreed to join the plot. The assassin unwisely met with his fellow
conspirators at his lodgings, freely discussing the murder. The old woman overheard
everything and, when she was able to get away, went straight to the palace. Gallus heard
the evidence and punished those involved.
Ammianus Marcellinus mentions that a woman revealed a conspiracy against
Gallus among some low ranking soldiers. Constantia rewarded the woman and proclaimed her
joy that Gallus was safe (14.7.6). There is no mention of Magnentius in Ammianus and the
text relating to the plot follows chronologically after the fall of the usurper. If
Magnentius had devised a conspiracy, Ammianus' account would have reported it in Book 13
(which is unfortunately lost) with all other matters relating to his usurpation. It has
been demonstrated that the events Ammianus recorded in book 14 occurred anywhere from
December 353 through March 354. Zonarus, writing 800 years after Ammianus, placed the
conspiracy immediately following the battle of Mursa and is the only historian who reports
an assassination plot by Magnentius. Since additional evidence is lacking, Magnentius'
conspiracy against Gallus must be considered a fiction. 
Gallus proved not to be a success in the East and was soon in bitter
conflict with the people of Antioch and the administrators Constantius appointed.
Forgetting he was to be a mere figurehead, Gallus was soon conducting trials and
condemning Antiochenes on trivial charges, and a revolt of the Jews was savagely put down.
This kind of news caused Constantius to have second thoughts about his cousin, which were
exacerbated by his courtiers (Amm. 14.1.1).
Constantius needed to secure the Pannonian frontier before he could move
against Magnentius; he fought a battle against the Sarmatians and with the Danube secure
he could proceed to enter Italy.  While he prepared his forces for the invasion,
Constantius sent a fleet into the Mediterranean that secured Africa, Sicily and Spain from
the usurper. In August 352, Constantius' forces broke through into northern Italy and on
September 26, 352, Constantius' nominee Naeratius Cerealis, a maternal uncle of Gallus,
became praefectus urbi of Rome. By November, Magnentius had retreated to Gaul and
Constantius was holding court in Milan. Magnentius could still count on his loyal Gauls
for support and was able to piece together an army. Inflation must have been rampant in
his shrinking empire. Julian reports that Magnentius instituted a 50% property tax (Or.
1 34B) and a coinage reform introduced a new double centenionalis with little or no silver
that quickly was reduced in weight. This new coin is noteworthy for the unprecedented use
of Chi-Rho as a reverse type itself, not as part of the design. It has been suggested that
the use of this symbol by Magnentius was directed toward Orthodox Christians, in the hope
he could convince them to fight against the Arian Constantius. But, did Magnentius'
contemporaries view the Chi-Rho in this way?
The Chi-Rho had appeared in different non-Christian contexts. It was used by pagans to mark significant passages in papyri, with Chi-Rho standing for the Greek 'chreston', meaning good. The symbol may have been connected to the worship of the Sun or Mithras, but this is highly speculative. The Chi-Rho has been found depicted on grave goods with a mixture of other representations, such as Sol and Orpheus. Chi-Rho did not come into Christian usage until the reign of Constantine when its ambiguity made it a good choice for the design of the labarum.  The symbol had a double meaning, one for Christians and one for pagans, and both revered it. It allowed Constantine to pursue Christianity as a favored religion without offending pagans. Magnentius may have been making a universal appeal for support with his selection of Chi-Rho rather than directed toward a single group. 
In the spring or summer of 353, Constantius' army crossed the Cottian Alps into Gaul. Ammianus Marcellinus briefly noted (15.6.4) that the city of Trier, under the leadership of someone named Poemenius, declared the city for Constantius and refused entry to Decentius. Trier was an important city for Magnentius being one of his most active mints. The date of the revolt is uncertain but based on the evidence of the new double centenionalis struck for Magnentius at Trier, the revolt could not have occurred until the final months of his reign.  Constantius and Magnentius fought one final battle at Mons Seleucus, and the usurper was decisively defeated. Trapped in Lugdunum (modern Lyon), Magnentius committed suicide by stabbing himself with his sword (Athanasius says he hung himself. (Apol. Ad Const. 7.3)) on August 10 or 11. Before he killed himself, Magnentius is reported to have killed a younger brother and his mother (Sozomen H.E. 4.7; Socrates H.E. 2.22; Philostorg 3.26). Decentius, to whom Magnentius had sent an appeal for help, learned of his brother's death on the march at Sens, where he hanged himself on August 18 (Zos. 2.54).
Following the death of Magnentius, Constantius sought out his followers for punishment. Ammianus mentions the fate of Gerontius, who was tortured and then banished (14.5.1). But worse was to follow. In 354, Constantius sent Paul (known fittingly as Paul the Chain), one of his courtiers, to Britain to arrest several of Magnentius' officers who had fled to the island. Paul proceeded to capture his quarry, loading them down with chains and binding their hands with handcuffs. He also fabricated charges against innocent people and seized their property; he even implicating the subordinates of the governor, Martinus. The governor was horrified and threatened to resign as a way of exposing the criminal conduct of Paul. Unperturbed, Paul merely accused Martinus of crimes and placed him under arrest but the governor cheated his tormentor of his prize by taking his own life. Paul brought his victims to court, all suffering under the crushing weight of multiple chains, to be tortured, exiled and some executed (14.5.7ff).
The troops of Magnentius that Constantius
captured were sent to the East on account of their disloyalty. They were eventually posted
to Amida, which was laid siege by the Persians in 359. After starving the city for some
time, the Persian stormed the walls and there was a great slaughter of the defenders.
Those left alive became prisoners and were led away to Persia (Amm. 19.9). Remnants
of Magnentius' army still remained. When Julian first arrived in Gaul as Caesar, he put
together an army from the followers of Magnentius who had been forced into banditry to
survive. In this way, a few of the dead emperor's soldiers lived to have a measure of
vengeance against Constantius, following a different leader in a rebellion that took place
ten years after the ill-fated day when Magnentius suddenly appeared wearing purple robes (Libanius
Copyright (C) 1999 David A. Wend
1- S.D. Nichlas, A General Survey of Coinage in the Roman Empire AD 294-408 and its Relationship to Military Development (1995),168-72.
2 - Barnes, op.cit.,101-2;H.W. Bird, Aurelius Victor De Caesaribus (Liverpool 1993), 53 n. 7; A.H.M. Jones J.R. Martindale, and J. Morris “Magnus Decentius 3” The Prospography of the Later Roman Empire (Cambridge 1971).
3 - Late Roman historians tend to mix events rather than relate them in chronological order. The history of Zosimus is a good example. See (2.45.2) where the historian discusses both Gallus and Decentius without providing a reference date. Eutropius places the elevation of Decentius and Gallus following the battle of Mursa (10.12).
4 - It has been argued by the editors of Roman Imperial Coinage Volume VIII that these coins cannot be die-linked to the issues of Magnentius and the legend MAG DECENTIVS NOB CAES, used with these coins, are a later device. Overall, the style and flan size supposedly links these coins to the VICTORIA series of 351.
5 - See the discussion in Roman Imperial Coinage Vol. VIII pp. 241-2. Contrary to Zonarus, who places Decentius’ elevation at Milan, the editors of RIC felt this event happened at Rome. The editors are also convinced that early Rome issues for Decentius are consistent with his elevation in the spring of 351. They place emphasis that there are no precious metal issues for the Caesar at Aquileia prior to 351. However, Decentius’ coinage appears to have been issued sporatically from mint to mint. For example, his at Amiens is scanty when one would expect an abundance at a mint with a family connection. I am not convinced that Decentius’ Roman coinage proves a later date for his elevation. Based upon numismatic evidence, historical analysis and the necessity for Magnentius’ brother to play a greater role, the summer of 350 is the likeliest time frame.
6 - R.Turcan,The Cults of the Roman Empire(Oxford 1996) 70;Barnes, op. cit., 102.
7 - R. MacMullen,Christianizing the Roman Empire AD 100-400 (New Haven 1984) 44-7; P. Chauvin,A Chronicle of the Last Pagans (Cambridge 1990) 36-40.
8 - Zosimus wrote the most complete account of Magnentius’ invasion of Panonia, but at times it is confusing. At one point, Constantius has Magnentius within his grasp but lets him go so they can fight a battle at Cibalis, where Constantine had triumphed over Licinius.
9 - Bidez,op cit., 314. Following the death of Magnentius, Silvanus was put in charge of the Gallic army tp end German raids into the province. He was too successful, and Constantius’ courtiers falsely portrayed him plotting rebellion. When the emperor ordered Silvanus recalled, the general was forced to rebel to save himself and was murdered after 28 days as emperor (August 355).
10 - R.M. Frakes,”Ammianus Marcellinus and Zonarus on a Late Roman Assassination Plot”,Historia 46(1997) 121-28.
11 - Barnes,op. cit.,160.
12 - According to Eusebius (Life of Constantine 1.28ff), the labarum was a long spear, covered in gold, and joined by a transverse bar, giving it the appearance of a cross. At the top, was a golden wreath set with precious stones with the Chi-Rho placed in the center.
13 - Grant, op. cit.,141-5;MacMullen,op. cit.,77-8.
14 - J.P.C. Kent,”The Revolt of Trier Against Magnentius”,Numismatic Chronicle (1959).