Constantine I (27 February 272 – 22 May 337), also known as Constantine the Great, was Roman emperor from AD 306 to 337 and the first Roman emperor to convert to Christianity. He played a pivotal role in elevating the status of Christianity in the Roman Empire, the Edict of Milan decriminalising Christian practice and ceasing Christian persecution. This was a turning point in the Christianisation of the Roman Empire. He founded the city of Constantinople (now Istanbul) and made it the capital of the Empire, which it remained for over a millennium.
Born in Naissus, a city located in the province of Moesia Superior (now Niš, Serbia), Constantine was the son of Flavius Constantius, a Roman army officer from Moesia Superior, who would become one of the four emperors of the Tetrarchy. His mother, Helena, was a Greek woman of low birth, probably from Bithynia. Later canonised as a saint, she is credited for the conversion of her son in some traditions, though others believe that Constantine converted her. He served with distinction under emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces against the Persians, before being recalled to the west in AD 305 to fight with his father in the province of Britannia. After his father's death in 306, Constantine was proclaimed as augustus (emperor) by his army at Eboracum (York, England). He eventually emerged victorious in the Civil wars of the Tetrarchy against the emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.
Upon his accession, Constantine enacted many reforms to strengthen the empire. He restructured the government, separating civil and military authorities. To combat inflation, he introduced the solidus, a new gold coin that became the standard for Byzantine and European currencies for more than a thousand years. He disbanded the Praetorian Guard, which had supported Maxentius. The Roman army was reorganised to consist of mobile units (comitatenses), often around the emperor, to serve on campaigns against external enemies or Roman rebels, and frontier-garrison troops (limitanei) which were capable of countering barbarian raids, but less and less capable of countering full-scale barbarian invasions. Constantine pursued campaigns against the tribes on the Roman frontiers—such as the Franks, the Alemanni, the Goths, and the Sarmatians—and resettled territories abandoned by his predecessors during the Crisis of the Third Century with citizens of Roman society.
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Although Constantine lived much of his life as a pagan, he later became a catechumen, as he began to favour Christianity in 312, finally being baptised by Eusebius of Nicomedia, an Arian bishop. He played an influential role in the proclamation of the Edict of Milan in 313, which legalized Christianity in the Roman Empire. He convoked the First Council of Nicaea in 325, which produced the Christian statement of belief known as the Nicene Creed. On his orders, the Church of the Holy Sepulchre was built at the site claimed to be the tomb of Jesus in Jerusalem and was deemed the holiest place in Christendom. He has historically been referred to as the "First Christian Emperor" but while he did favour the Christian Church, some modern scholars debate his beliefs and even his comprehension of Christianity. He is venerated as a saint in Eastern Christianity and parts of Western Christianity, and he did much to push Christianity towards the mainstream of Roman culture.
The age of Constantine marked a distinct epoch in the history of the Roman Empire and a pivotal moment in the evolution from classical antiquity to the Middle Ages. He built a new imperial residence in the city of Byzantium, which was officially renamed New Rome, while also taking on the name Constantinople in his honour. It subsequently served as the capital of the empire for more than a thousand years—with the Eastern Roman Empire for most of that period commonly referred to retrospectively as the Byzantine Empire in English. In leaving the empire to his sons and other members of the Constantinian dynasty, Constantine's immediate political legacy was the replacement of Diocletian's Tetrarchy with the principle of dynastic succession. His memory was held in high regard during the lifetime of his children and for centuries after his reign. The medieval church held him up as a paragon of virtue, while secular rulers invoked him as a symbol of imperial legitimacy. The rediscovery of anti-Constantinian sources in the early Renaissance engendered more critical appraisals of his reign, with modern and contemporary scholarship often seeking to balance the extremes of earlier accounts.
Early life
Constantine was born on 27 February 272. While his official birthday is recorded in sources, his year of birth is not, and scholars have given several estimates between 271 and 280, with most leaning for 272 or 273. However, the evidence points to 272 being the correct year. He was born inside the city of Naissus, during a time when the unity of the Empire was threatened by the breakaway wars of the Palmyrene Empire. The city (modern Niš, Serbia) was located in Dardania within the province of Moesia Superior. His father was Flavius Constantius, an Illyrian or, according to his nephew, Julian The Apostate, a Thracian. His original full name, as well as that of his father, is not known. His praenomen is variously given as Lucius, Marcus and Gaius. Whatever the case, praenomina had already disappeared from most public records by this time. He also adopted the name "Valerius", the nomen of emperor Diocletian, following his father's ascension as caesar.
Constantine probably spent little time with his father who was an officer in the Roman army, part of Emperor Aurelian's imperial bodyguard. Being described as a tolerant and politically skilled man, Constantius advanced through the ranks, earning the governorship of Dalmatia from Emperor Diocletian, another of Aurelian's companions from Illyricum, in 284 or 285. Constantine's mother was Helena, a Greek woman of low social standing, possibly from Drepanum (later renamed Helenopolis) of Bithynia, which would likely have made her a Greek-speaker. It is uncertain whether she was legally married to Constantius or merely his concubine. Constantine's own language was Latin, and during his public speeches in the church councils, which were held in Greek, he needed Greek translators.
In April 286 Diocletian declared Maximian, another colleague from Illyricum, his co-emperor. Each emperor would have his own court, his own military and administrative faculties, and each would rule with a separate praetorian prefect as chief lieutenant. Maximian ruled in the West, from his capitals at Mediolanum (Milan, Italy) or Augusta Treverorum (Trier, Germany), while Diocletian ruled in the East, from Nicomedia (İzmit, Turkey). The division was merely pragmatic: the empire was called "indivisible" in official panegyric, and both emperors could move freely throughout the empire. In 288, Maximian appointed Constantius to serve as his praetorian prefect in Gaul. Constantius left Helena to marry Maximian's stepdaughter Theodora in 288 or 289.
Diocletian divided the empire again in 293, appointing two caesars to rule over further subdivisions of East and West. Each would be subordinate to his respective augustus but would act with supreme authority in his assigned lands. This system would later be called the Tetrarchy. Diocletian's first appointee for the office of Caesar was Constantius; his second was Galerius, a native of Felix Romuliana. According to Lactantius, Galerius was a brutal, animalistic man. Although he shared the paganism of Rome's aristocracy, he seemed to them an alien figure, a semi-barbarian. On 1 March, Constantius was promoted to the office of Caesar, and dispatched to Gaul to fight the rebels Carausius and Allectus. In spite of meritocratic overtones, the Tetrarchy retained vestiges of hereditary privilege, and Constantine became the prime candidate for future appointment as Caesar as soon as his father took the position. Constantine went to the court of Diocletian, where he lived as his father's heir presumptive.
Constantine received a formal education at Diocletian's court, where he learned Latin literature, Greek, and philosophy. The cultural environment in Nicomedia was open, fluid, and socially mobile; in it, Constantine could mix with intellectuals both pagan and Christian. He may have attended the lectures of Lactantius, a Christian scholar of Latin in the city. Because Diocletian did not completely trust Constantius—none of the Tetrarchs fully trusted their colleagues—Constantine was held as something of a hostage, a tool to ensure Constantius' best behavior. Constantine was nonetheless a prominent member of the court: he fought for Diocletian and Galerius in Asia and served in a variety of tribunates; he campaigned against barbarians on the Danube in 296 and fought the Persians under Diocletian in Syria in 297, as well as under Galerius in Mesopotamia in 298–299. By late 305, according to some, he had become a tribune of the first order, a tribunus ordinis primi.
Constantine had returned to Nicomedia from the eastern front by the spring of 303, in time to witness the beginnings of Diocletian's "Great Persecution", the most severe persecution of Christians in Roman history. In late 302, Diocletian and Galerius sent a messenger to the oracle of Apollo at Didyma with an inquiry about Christians. Constantine could recall his presence at the palace when the messenger returned and Diocletian accepted the imperial court's demands for universal persecution. On 23 February 303, Diocletian ordered the destruction of Nicomedia’s new church, condemned its scriptures to the flames, and had its treasures seized. In the months that followed, churches and scriptures were destroyed, Christians were deprived of official ranks, and priests were imprisoned. It is unlikely that Constantine played any role in the persecution. In his later writings, he attempted to present himself as an opponent of Diocletian's "sanguinary edicts" against the "Worshippers of God", but nothing indicates that he opposed it effectively at the time. Although no contemporary Christian challenged Constantine for his inaction during the persecutions, it remained a political liability throughout his life.
On 1 May 305 Diocletian, as a result of a debilitating sickness taken in the winter of 304–305, announced his resignation. In a parallel ceremony in Milan, Maximian did the same. Lactantius states that Galerius manipulated the weakened Diocletian into resigning and forced him to accept Galerius' allies in the imperial succession. According to Lactantius, the crowd listening to Diocletian's resignation speech believed, until the last moment, that Diocletian would choose Constantine and Maxentius (Maximian's son) as his successors. It was not to be: Constantius and Galerius were promoted to augusti, while Severus and Maximinus, Galerius' nephew, were appointed their caesars respectively. Constantine and Maxentius were ignored.
Some of the ancient sources detail plots that Galerius made on Constantine's life in the months following Diocletian's abdication. They assert that Galerius assigned Constantine to lead an advance unit in a cavalry charge through a swamp on the middle Danube, made him enter into single combat with a lion, and attempted to kill him in hunts and wars. Constantine always emerged victorious: the lion emerged from the contest in a poorer condition than Constantine; Constantine returned to Nicomedia from the Danube with a Sarmatian captive to drop at Galerius' feet. It is uncertain how much these tales can be trusted.
In the West
Constantine recognised the implicit danger in remaining at Galerius' court, where he was held as a virtual hostage. His career depended on being rescued by his father in the West. Constantius was quick to intervene. In the late spring or early summer of 305, Constantius requested leave for his son to help him campaign in Britain. After a long evening of drinking, Galerius granted the request. Constantine's later propaganda describes how he fled the court in the night, before Galerius could change his mind. He rode from post-house to post-house at high speed, hamstringing every horse in his wake. By the time Galerius awoke the following morning, Constantine had fled too far to be caught. Constantine joined his father in Gaul, at Bononia (Boulogne) before the summer of 305.
From Bononia they crossed the English Channel to Britain and made their way to Eboracum (modern York), capital of the province of Britannia Secunda and home to a large military base. Constantine was able to spend a year in northern Britain at his father's side, campaigning against the Picts beyond Hadrian's Wall in the summer and autumn. Constantius' campaign, like that of Septimius Severus before it, probably advanced far into the north without achieving great success. Constantius had become severely sick over the course of his reign and died on 25 July 306 in Eboracum. Before dying, he declared his support for raising Constantine as emperor. The Alamannic king Chrocus, a barbarian taken into service under Constantius, then proclaimed Constantine as augustus. The troops loyal to Constantius' memory followed him in acclamation. Gaul and Britain quickly accepted his rule; Hispania, which had been in his father's domain for less than a year, rejected it.
Constantine sent Galerius an official notice of Constantius' death and his own acclamation. Along with the notice, he included a portrait of himself in the robes of an Augustus. The portrait was wreathed in bay. He requested recognition as heir to his father's throne and passed off responsibility for his unlawful ascension on his army, claiming they had "forced it upon him". Galerius was put into a fury by the message; he almost set the portrait and messenger on fire. His advisers calmed him and argued that outright denial of Constantine's claims would mean certain war. Galerius was compelled to compromise: he granted Constantine the title "caesar" rather than "augustus" (the latter office went to Severus instead). Wishing to make it clear that he alone gave Constantine legitimacy, Galerius personally sent Constantine the emperor's traditional purple robes. Constantine accepted the decision, knowing that it would remove doubts as to his legitimacy.
Reign
Constantine's share of the empire consisted of Britain, Gaul, and Spain. He commanded one of the largest Roman armies, stationed along the strategically important Rhine frontier. He remained in Britain after his promotion to emperor, driving back the tribes of the Picts and securing his control in the northwestern dioceses. He completed the military bases begun under his father's rule and ordered the region's roads repaired. He then left for Augusta Treverorum (Trier) in Gaul, the Tetrarchic capital of the northwestern Roman Empire. The Franks learned of Constantine's acclamation and invaded Gaul across the lower Rhine over the winter of 306–307. He drove them back beyond the Rhine and captured kings Ascaric and Merogais; the kings and their soldiers were fed to the beasts of Trier Amphitheater in the adventus (arrival) celebrations which followed.
Constantine began a major expansion of Trier. He strengthened the circuit wall around the city with military towers and fortified gates, and he began building a palace complex in the northeastern part of the city. To the south of his palace, he ordered the construction of a large formal audience hall and a massive imperial bathhouse. He sponsored many building projects throughout Gaul during his tenure as emperor of the West, especially in Augustodunum (Autun) and Arelate (Arles). According to Lactantius, Constantine followed a tolerant policy towards Christianity, although he may not have yet adopted the Christian faith. There is no consensus among scholars on Constantine's religious convictions at the beginning of his reign, and some suggest an adoption of Christianity from his youth. Regardless, he probably judged toleration a more sensible policy than open persecution and a way to distinguish himself from the "great persecutor" Galerius. He decreed a formal end to persecution and returned to Christians all that they had lost under the first of the persecuting edicts.
Constantine was largely untried and had a hint of illegitimacy about him; he relied on his father's reputation in his early propaganda, which gave as much coverage to his father's deeds as to his. His military skill and building projects, however, soon gave the panegyrist the opportunity to comment favourably on the similarities between father and son, and Eusebius remarked that Constantine was a "renewal, as it were, in his own person, of his father's life and reign". Constantinian coinage, sculpture, and oratory also show a tendency for disdain towards the "barbarians" beyond the frontiers. He minted a coin issue after his victory over the Alemanni which depicts weeping and begging Alemannic tribesmen, "the Alemanni conquered" beneath the phrase "Romans' rejoicing". There was little sympathy for these enemies; as his panegyrist declared, "It is a stupid clemency that spares the conquered foe."
Maxentius's rebellion
Following Galerius's recognition of Constantine as caesar, Constantine's portrait was brought to Rome, as was customary. Maxentius mocked the portrait's subject as the son of a harlot and lamented his own powerlessness. Maxentius, envious of Constantine's authority, seized the title of emperor on 28 October 306. Galerius refused to recognise him but failed to unseat him. Severus was sent against Maxentius in April 307, but during the campaign, Severus' armies, previously under command of Maxentius' father Maximian, defected, and Severus was seized and imprisoned. Maximian, brought out of retirement by his son's rebellion, left for Gaul to confer with Constantine. He offered to marry his daughter Fausta to Constantine and elevate him to augustan rank. In return, Constantine would reaffirm the old family alliance between Maximian and Constantius and offer support to Maxentius' cause in Italy. Constantine accepted and married Fausta in Trier in summer 307. Constantine gave Maxentius his meagre support, offering Maxentius political recognition.
Constantine remained aloof from the Italian conflict, however. Over the spring and summer of 307 he had left Gaul for Britain to avoid any involvement in the Italian turmoil; now, instead of giving Maxentius military aid, he sent his troops against Germanic tribes along the Rhine. In 308, he raided the territory of the Bructeri and made a bridge across the Rhine at Colonia Agrippinensium (Cologne). In 310, he marched to the northern Rhine and fought the Franks. When not campaigning, he toured his lands advertising his benevolence and supporting the economy and the arts. His refusal to participate in the war increased his popularity among his people and strengthened his power base in the West. Maximian returned to Rome in the winter of 307–308 but soon fell out with his son. In early 308, after a failed attempt to usurp Maxentius' title, Maximian returned to Constantine's court.
On 11 November 308 Galerius called a general council at the military city of Carnuntum (Petronell-Carnuntum, Austria) to resolve the instability in the western provinces. In attendance were Diocletian, briefly returned from retirement, Galerius, and Maximian. Maximian was forced to abdicate again and Constantine was again demoted to caesar. Licinius, one of Galerius' old military companions, was appointed augustus in the western regions. The new system did not last long: Constantine refused to accept the demotion and continued to style himself as augustus on his coinage, even as other members of the Tetrarchy referred to him as a caesar on theirs. Maximinus was frustrated that he had been passed over for promotion while the newcomer Licinius had been raised to the office of augustus and demanded that Galerius promote him. Galerius offered to call both Maximinus and Constantine "sons of the augusti", but neither accepted the new title. By the spring of 310, Galerius was referring to both men as augusti.
Maximian's rebellion
In 310 a dispossessed Maximian rebelled against Constantine while Constantine was away campaigning against the Franks. Maximian had been sent south to Arles with a contingent of Constantine's army, in preparation for any attacks by Maxentius in southern Gaul. He announced that Constantine was dead and took up the imperial purple. In spite of a large donative pledge to any who would support him as emperor, most of Constantine's army remained loyal to their emperor, and Maximian was soon compelled to leave. When Constantine heard of the rebellion, he abandoned his campaign against the Franks and marched his army up the Rhine. At Cabillunum (Chalon-sur-Saône), he moved his troops onto waiting boats to row down the slow waters of the Saône to the quicker waters of the Rhone. He disembarked at Lugdunum (Lyon). Maximian fled to Massilia (Marseille), a town better able to withstand a long siege than Arles. It made little difference, however, as loyal citizens opened the rear gates to Constantine. Maximian was captured and reproved for his crimes. Constantine granted some clemency but strongly encouraged his suicide. In July 310, Maximian hanged himself.
In spite of the earlier rupture in their relations, Maxentius was eager to present himself as his father's devoted son after his death. He began minting coins with his father's deified image, proclaiming his desire to avenge Maximian's death. Constantine initially presented the suicide as an unfortunate family tragedy. By 311, however, he was spreading another version. According to this, after Constantine had pardoned him, Maximian planned to murder Constantine in his sleep. Fausta learned of the plot and warned Constantine, who put a eunuch in his own place in bed. Maximian was apprehended when he killed the eunuch and was offered suicide, which he accepted. Along with using propaganda, Constantine instituted a damnatio memoriae on Maximian, destroying all inscriptions referring to him and eliminating any public work bearing his image.
The death of Maximian required a shift in Constantine's public image. He could no longer rely on his connection to the elder Emperor Maximian and needed a new source of legitimacy. In a speech delivered in Gaul on 25 July 310, the anonymous orator reveals a previously unknown dynastic connection to Claudius II, a 3rd-century emperor famed for defeating the Goths and restoring order to the empire. Breaking away from tetrarchic models, the speech emphasises Constantine's ancestral prerogative to rule, rather than principles of imperial equality. The new ideology expressed in the speech made Galerius and Maximian irrelevant to Constantine's right to rule. Indeed, the orator emphasises ancestry to the exclusion of all other factors: "No chance agreement of men, nor some unexpected consequence of favour, made you emperor," the orator declares to Constantine.
The oration also moves away from the religious ideology of the Tetrarchy, with its focus on twin dynasties of Jupiter and Hercules. Instead, the orator proclaims that Constantine experienced a divine vision of Apollo and Victory granting him laurel wreaths of health and a long reign. In the likeness of Apollo, Constantine recognised himself as the saving figure to whom would be granted "rule of the whole world", as the poet Virgil had once foretold. The oration's religious shift is paralleled by a similar shift in Constantine's coinage. In his early reign, the coinage of Constantine advertised Mars as his patron. From 310 on, Mars was replaced by Sol Invictus, a god conventionally identified with Apollo. There is little reason to believe that either the dynastic connection or the divine vision are anything other than fiction, but their proclamation strengthened Constantine's claims to legitimacy and increased his popularity among the citizens of Gaul.
Civil wars
War against Maxentius
By the middle of 310 Galerius had become too ill to involve himself in imperial politics. His final act survives: a letter to provincials posted in Nicomedia on 30 April 311, proclaiming an end to the persecutions, and the resumption of religious toleration.
Eusebius maintains "divine providence [...] took action against the perpetrator of these crimes" and gives a graphic account of Galerius' demise:
"Without warning suppurative inflammation broke out round the middle of his genitals, then a deep-seated fistula ulcer; these ate their way incurably into his innermost bowels. From them came a teeming indescribable mass of worms, and a sickening smell was given off, for the whole of his hulking body, thanks to over eating, had been transformed even before his illness into a huge lump of flabby fat, which then decomposed and presented those who came near it with a revolting and horrifying sight."
Galerius died soon after the edict's proclamation, destroying what little remained of the Tetrarchy. Maximinus mobilised against Licinius and seized Asia Minor. A hasty peace was signed on a boat in the middle of the Bosphorus. While Constantine toured Britain and Gaul, Maxentius prepared for war. He fortified northern Italy and strengthened his support in the Christian community by allowing it to elect Eusebius as bishop of Rome.
Maxentius' rule was nevertheless insecure. His early support dissolved in the wake of heightened tax rates and depressed trade; riots broke out in Rome and Carthage; and Domitius Alexander was able to briefly usurp his authority in Africa. By 312, he was a man barely tolerated, not one actively supported, even among Christian Italians. In the summer of 311, Maxentius mobilised against Constantine while Licinius was occupied with affairs in the East. He declared war on Constantine, vowing to avenge his father's "murder". To prevent Maxentius from forming an alliance against him with Licinius, Constantine forged his own alliance with Licinius over the winter of 311–312 and offered him his sister Constantia in marriage. Maximinus considered Constantine's arrangement with Licinius an affront to his authority. In response, he sent ambassadors to Rome, offering political recognition to Maxentius in exchange for a military support, which Maxentius accepted. According to Eusebius, inter-regional travel became impossible, and there was military buildup everywhere. There was "not a place where people were not expecting the onset of hostilities every day".
Constantine's advisers and generals cautioned against preemptive attack on Maxentius; even his soothsayers recommended against it, stating that the sacrifices had produced unfavourable omens. Constantine, with a spirit that left a deep impression on his followers, inspiring some to believe that he had some form of supernatural guidance, ignored all these cautions. Early in the spring of 312, Constantine crossed the Cottian Alps with a quarter of his army, a force numbering about 40,000. The first town his army encountered was Segusium (Susa, Italy), a heavily fortified town that shut its gates to him. Constantine ordered his men to set fire to its gates and scale its walls. He took the town quickly. Constantine ordered his troops not to loot the town and advanced into northern Italy.
At the approach to the west of the important city of Augusta Taurinorum (Turin, Italy), Constantine met a large force of heavily armed Maxentian cavalry. In the ensuing Battle of Turin Constantine's army encircled Maxentius' cavalry, flanked them with his own cavalry, and dismounted them with blows from his soldiers' iron-tipped clubs. Constantine's armies emerged victorious. Turin refused to give refuge to Maxentius' retreating forces, opening its gates to Constantine instead. Other cities of the north Italian plain sent Constantine embassies of congratulation for his victory. He moved on to Milan, where he was met with open gates and jubilant rejoicing. Constantine rested his army in Milan until mid-summer 312, when he moved on to Brixia (Brescia).
Brescia's army was easily dispersed, and Constantine quickly advanced to Verona where a large Maxentian force was camped. Ruricius Pompeianus, general of the Veronese forces and Maxentius' praetorian prefect, was in a strong defensive position since the town was surrounded on three sides by the Adige. Constantine sent a small force north of the town in an attempt to cross the river unnoticed. Ruricius sent a large detachment to counter Constantine's expeditionary force but was defeated. Constantine's forces successfully surrounded the town and laid siege. Ruricius gave Constantine the slip and returned with a larger force to oppose Constantine. Constantine refused to let up on the siege and sent only a small force to oppose him. In the desperately fought encounter that followed, Ruricius was killed and his army destroyed. Verona surrendered soon afterwards, followed by Aquileia, Mutina (Modena), and Ravenna. The road to Rome was now wide open to Constantine.
Maxentius prepared for the same type of war he had waged against Severus and Galerius: he occupied Rome and prepared for a siege. He still controlled Rome's Praetorian Guard, was well-stocked with African grain, and was surrounded on all sides by the seemingly impregnable Aurelian Walls. He ordered all bridges across the Tiber cut, reportedly on the counsel of the gods, and left the rest of central Italy undefended; Constantine secured that region's support without challenge. Constantine progressed slowly along the Via Flaminia, allowing the weakness of Maxentius to draw his regime further into turmoil. Maxentius' support continued to weaken: at chariot races on 27 October, the crowd openly taunted Maxentius, shouting that Constantine was invincible. Maxentius, no longer certain that he would emerge from a siege victorious, built a temporary boat bridge across the Tiber in preparation for a field battle against Constantine. On 28 October 312, the sixth anniversary of his reign, he approached the keepers of the Sibylline Books for guidance. The keepers prophesied that, on that very day, "the enemy of the Romans" would die. Maxentius advanced north to meet Constantine in battle.
Milvian Bridge
Maxentius' forces were still twice the size of Constantine's, and he organised them in long lines facing the battle plain with their backs to the river. Constantine's army arrived on the field bearing unfamiliar symbols on their standards and their shields. According to Lactantius "Constantine was directed in a dream to cause the heavenly sign to be delineated on the shields of his soldiers, and so to proceed to battle. He did as he had been commanded, and he marked on their shields the letter Χ, with a perpendicular line drawn through it and turned round thus at the top, being the cipher of Christ. Having this sign (☧), his troops stood to arms." Eusebius describes a vision that Constantine had while marching at midday in which "he saw with his own eyes the trophy of a cross of light in the heavens, above the sun, and bearing the inscription, In Hoc Signo Vinces" ("In this sign thou shalt conquer"). In Eusebius' account, Constantine had a dream the following night in which Christ appeared with the same heavenly sign and told him to make an army standard in the form of the labarum. Eusebius is vague about when and where these events took place, but it enters his narrative before the war begins against Maxentius. He describes the sign as Chi (Χ) traversed by Rho (Ρ) to form ☧, representing the first two letters of the Greek word ΧΡΙΣΤΟΣ (Christos). A medallion was issued at Ticinum in 315 which shows Constantine wearing a helmet emblazoned with the Chi Rho, and coins issued at Siscia in 317/318 repeat the image. The figure was otherwise rare and is uncommon in imperial iconography and propaganda before the 320s. It was not completely unknown, however, being an abbreviation of the Greek word chrēston (good), having previously appeared on the coins of Ptolemy III Euergetes in the 3rd century BC. Following Constantine, centuries of Christians invoked the miraculous or the supernatural when justifying or describing their warfare.
Constantine deployed his own forces along the whole length of Maxentius' line. He ordered his cavalry to charge, and they broke Maxentius' cavalry. He then sent his infantry against Maxentius' infantry, pushing many into the Tiber where they were slaughtered and drowned. The battle was brief, and Maxentius' troops were broken before the first charge. His horse guards and praetorians initially held their position, but they broke under the force of a Constantinian cavalry charge; they also broke ranks and fled to the river. Maxentius rode with them and attempted to cross the bridge of boats (Ponte Milvio), but he was pushed into the Tiber and drowned by the mass of his fleeing soldiers.
In Rome
Constantine entered Rome on 29 October 312 and staged a grand adventus in the city which was met with jubilation. Maxentius' body was fished out of the Tiber and decapitated, and his head was paraded through the streets for all to see. After the ceremonies, the disembodied head was sent to Carthage, and Carthage offered no further resistance. Unlike his predecessors, Constantine neglected to make the trip to the Capitoline Hill and perform customary sacrifices at the Temple of Jupiter. However, he did visit the Senatorial Curia Julia, and he promised to restore its ancestral privileges and give it a secure role in his reformed government; there would be no revenge against Maxentius' supporters. In response, the Senate decreed him "title of the first name", which meant that his name would be listed first in all official documents, and they acclaimed him as "the greatest augustus". He issued decrees returning property that was lost under Maxentius, recalling political exiles, and releasing Maxentius' imprisoned opponents.
An extensive propaganda campaign followed, during which Maxentius' image was purged from all public places. He was written up as a "tyrant" and set against an idealised image of Constantine the "liberator". Eusebius is the best representative of this strand of Constantinian propaganda. Maxentius' rescripts were declared invalid, and the honours that he had granted to leaders of the Senate were also invalidated. Constantine also attempted to remove Maxentius' influence on Rome's urban landscape. All structures built by him were rededicated to Constantine, including the Temple of Romulus and the Basilica of Maxentius. At the focal point of the basilica, a stone statue was erected of Constantine holding the Christian labarum in its hand. Its inscription bore the message which the statue illustrated: "By this sign, Constantine had freed Rome from the yoke of the tyrant."
Constantine also sought to upstage Maxentius' achievements. For example, the Circus Maximus was redeveloped so that its seating capacity was 25 times larger than that of Maxentius' racing complex on the Via Appia. Maxentius' strongest military supporters were neutralised when Constantine disbanded the Praetorian Guard and Imperial Horse Guard. The tombstones of the Imperial Horse Guard were ground up and used in a basilica on the Via Labicana, and their former base was redeveloped into the Lateran Basilica on 9 November 312—barely two weeks after Constantine captured the city. The Legio II Parthica was removed from Albano Laziale, and the remainder of Maxentius' armies were sent to do frontier duty on the Rhine.
Wars against Licinius
In the following years, Constantine gradually consolidated his military superiority over his rivals in the crumbling Tetrarchy. In 313, he met Licinius in Milan to secure their alliance by the marriage of Licinius and Constantine's half-sister Constantia. During this meeting, the emperors agreed on the so-called Edict of Milan, officially granting full tolerance to Christianity and all religions in the empire. The document had special benefits for Christians, legalising their religion and granting them restoration for all property seized during Diocletian's persecution. It repudiates past methods of religious coercion and used only general terms to refer to the divine sphere—"Divinity" and "Supreme Divinity", summa divinitas. The conference was cut short, however, when news reached Licinius that his rival Maximinus had crossed the Bosporus and invaded European territory. Licinius departed and eventually defeated Maximinus, gaining control over the entire eastern half of the Roman Empire. Relations between the two remaining emperors deteriorated, as Constantine suffered an assassination attempt at the hands of a character that Licinius wanted elevated to the rank of Caesar; Licinius, for his part, had Constantine's statues in Emona destroyed. In either 314 or 316 the two augusti fought against one another at the Battle of Cibalae, with Constantine being victorious. They clashed again at the Battle of Mardia in 317 and agreed to a settlement in which Constantine's sons Crispus and Constantine II, and Licinius' son Licinius Junior were made caesars. After this arrangement, Constantine ruled the dioceses of Pannonia and Macedonia and took residence at Sirmium, whence he could wage war on the Goths and Sarmatians in 322, and on the Goths in 323, defeating and killing their leader Rausimod.
In 320 Licinius allegedly reneged on the religious freedom promised by the Edict of Milan and began to oppress Christians anew, generally without bloodshed, but resorting to confiscations and sacking of Christian office-holders. Although this characterisation of Licinius as anti-Christian is somewhat doubtful, the fact is that he seems to have been far less open in his support of Christianity than Constantine. Therefore, Licinius was prone to see the Church as a force more loyal to Constantine than to the Imperial system in general, as the explanation offered by the Church historian Sozomen.
This dubious arrangement eventually became a challenge to Constantine in the West, climaxing in the great civil war of 324. Constantine's Christian eulogists present the war as a battle between Christianity and paganism; Licinius, aided by Gothic mercenaries, represented the past and ancient paganism, while Constantine and his Franks marched under the standard of the labarum. Outnumbered but fired by their zeal, Constantine's army emerged victorious in the Battle of Adrianople. Licinius fled across the Bosphorus and appointed Martinian, his magister officiorum, as nominal augustus in the West, but Constantine next won the Battle of the Hellespont and finally the Battle of Chrysopolis on 18 September 324. Licinius and Martinian surrendered to Constantine at Nicomedia on the promise their lives would be spared: they were sent to live as private citizens in Thessalonica and Cappadocia respectively, but in 325 Constantine accused Licinius of plotting against him and had them both arrested and hanged; Licinius' son (the son of Constantine's half-sister) was killed in 326. Thus Constantine became the sole emperor of the Roman Empire.
Later rule
Foundation of Constantinople
Diocletian had chosen Nicomedia in the East as his capital during the Tetrarchy—not far from Byzantium, well situated to defend Thrace, Asia, and Egypt, all of which had required his military attention. Constantine had recognised the shift of the empire from the remote and depopulated West to the richer cities of the East, and the military strategic importance of protecting the Danube from barbarian excursions and Asia from a hostile Persia in choosing his new capital as well as being able to monitor shipping traffic between the Black Sea and the Mediterranean. Licinius' defeat came to represent the defeat of a rival centre of pagan and Greek-speaking political activity in the East, as opposed to the Christian and Latin-speaking Rome, and it was proposed that a new Eastern capital should represent the integration of the East into the Roman Empire as a whole, as a centre of learning, prosperity, and cultural preservation for the whole of the Eastern Roman Empire. Among the various locations proposed for this alternative capital, Constantine appears to have toyed earlier with Serdica (present-day Sofia), as he was reported saying that "Serdica is my Rome". Sirmium and Thessalonica were also considered. Eventually, however, Constantine decided to work on the Greek city of Byzantium, which offered the advantage of having already been extensively rebuilt on Roman patterns of urbanism during the preceding century by Septimius Severus and Caracalla, who had already acknowledged its strategic importance. The city was thus founded in 324, dedicated on 11 May 330 and renamed Constantinopolis ("Constantine's City" or Constantinople in English). Special commemorative coins were issued in 330 to honour the event. The new city was later protected by the relics of the True Cross, the Rod of Moses and other holy relics, though a cameo now at the Hermitage Museum also represented Constantine crowned by the tyche of the new city. The figures of old gods were either replaced or assimilated into a framework of Christian symbolism. Generations later there was the story that a divine vision led Constantine to this spot, and an angel no one else could see led him on a circuit of the new walls. The capital would often be compared to the 'old' Rome as Nova Roma Constantinopolitana, the "New Rome of Constantinople".
Religion and religious policy
Constantine was the first emperor to stop the persecution of Christians and to legalise Christianity, along with all other religions and cults in the Roman Empire. In February 313, he met with Licinius in Milan and developed the Edict of Milan, which stated that Christians should be allowed to follow their faith without oppression. This removed penalties for professing Christianity, under which many had been martyred previously, and it returned confiscated Church property. The edict protected all religions from persecution, not only Christianity, allowing anyone to worship any deity that they chose. A similar edict had been issued in 311 by Galerius, senior emperor of the Tetrarchy, which granted Christians the right to practise their religion but did not restore any property to them. The Edict of Milan included several clauses which stated that all confiscated churches would be returned, as well as other provisions for previously persecuted Christians. Some scholars think that Helena adopted Christianity as an adult, and according to Eusebius she was converted by Constantine, but other historians debate whether Constantine adopted his mother Helena's Christianity in his youth or whether he adopted it gradually over the course of his life.
Constantine possibly retained the title of pontifex maximus which emperors bore as heads of the ancient Roman religion until Gratian renounced the title. According to Christian writers, Constantine was over 40 years old when he finally declared himself a Christian, making it clear that he owed his successes only to the protection of the Christian God. Despite these declarations of being a Christian, he waited to be baptised until on his deathbed, believing that the baptism would release him of any sins he committed in the course of carrying out his policies while emperor. He supported the Church financially, built basilicas, granted privileges to clergy (such as exemption from certain taxes), promoted Christians to high office, and returned property confiscated during the long period of persecution. His most famous building projects include the Church of the Holy Sepulchre and Old St. Peter's Basilica. In constructing the Old St. Peter's Basilica, Constantine went to great lengths to erect the basilica on top of St. Peter's resting place, so much so that it even affected the design of the basilica, including the challenge of erecting it on the hill where St. Peter rested, making its complete construction time over 30 years from the date Constantine ordered it to be built.
