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The Rise to Power of Constantine the Great

The Rise to Power of Constantine the Great

The rise to power of Constantine the Great

Constantine the Great is best remembered as the Emperor who did the most to turn the Romans into a Christian people and his reshaping of the Roman Empire through his sponsorship of the ‘Nova Roma’ in the east, Constantinople. 

Constantine was also a fighting leader who lead a life of warfare, both in terms of his struggle for mastery of the Roman Empire and against Rome’s external enemies.

Constantine’s father was initially Caesar in the west and later Augustus in the tetrarchy system in which Emperor Diocletian had divided the Empire into east and west. Each part of the empire having an ‘Augustus’ and a ‘Caesar’, the later being junior and the former co-emperors. This arrangement began to unravel in 306 AD after the abdication of the two Augusti in 305 AD and this disruption not only resulted in death and turmoil of civil war but vulnerability to external enemies beyond the frontiers.

In 305 AD, when Augusti Diocletion and Maximian abdicated, Galerius and Constantius (father of Constantine) were elevated by their predecessors to the role of ‘Augustus’ of the east and west respectively. However, the position of ‘Caesar’ in the west did not come to Constantine but instead to Severus, who was a friend of Galerius, and would therefore serve in the west as Constantius’ deputy.

Constantine was disappointed by these machinations and fled from the court of Galerius, where he had been compelled to live since the reign of Diocletian. He joined his father in Gaul, where he was preparing for a campaign in Britain. 

In 305 Constantine accompanied his father in campaign beyond the Hadrian’s Wall frontier against the Picts. By 7th January 306 Constantius had retired to Eboracum (York) where he claimed a victory and the title ‘Britannicus Maximus II’. Constantius was in poor health however and, despite planning a further campaign against the Picts, died on 25th July 306. Constantine was proclaimed by the legions as ‘Augustus’ following his father’s death but was convinced to accept the role of ‘Caesar’ by Galerius, who replaced Constantius with his friend Severus.

Constantine was responsible for Roman control in Britannia, Gaul and Hispania. He launched military campaigns against the Picts and the Alemanni and set about strengthening the frontiers. He defeated the Franks, who had invaded his territory, and fed their Kings, Ascaric and Merogais, to the beasts in the arena at Trier after his victory. However, his time as ‘Caesar’ was not all violence and war. He completed many building projects, notably in Trier, Arles and Autun. In a hint of his later religious stance, Constantine decreed a formal end to the persecution of Christians.

Constantine wasn’t the only son of an ‘Augusti’ to be passed over through Galerius’ schemes. Maximian’s son, Maxentius was similarly overlooked. However, Maxentius now had the example of Constantine to follow and moved to secure what he inevitably saw as his rightful inheritance. As fate would have it, Rome was in turmoil at the time as rumours were abound that the city would be subject to a change in taxation and lose it’s preferential status. Furthermore it was being said that the Praetorian Guard was to be disbanded. This lead to riots and the Praetorians took the opportunity to initiate a mutiny, offering Maxentius the imperial purple. Maxentius accepted and was publicly acclaimed Emperor on 28th October 306. Initially Maxentius referred to himself as ‘princeps invictus’ rather than ‘Caesar’ or ‘Augustus’ but Galerius (technically the senior ‘Augustus’) refused to recognise him. Maxentius was however recognised as Emperor in central and southern Italy as well as Africa. Severus retained power in northern Italy. 

Severus, suddenly disposed of much of his power, marched south to challenger Maxentius. His campaign went astray quickly though when many of his soldiers deserted him in favour of his enemy. Severus retreated to Ravenna with the remainder of his forces. Shortly afterwards, Severus surrendered to Maximian who at this point had come out of retirement to assume the title ‘Augustus’ again. Maximian agreed to spare Severus’ life but he was nevertheless paraded as a captive and either put to death or compelled to take his own life by Maximian in September 307. Galerius moved to depose Maxentius and Maximian, ruling jointly at this point, through an invasion of Italy but this failed after Maxentius bribed many of his troops to switch allegiance.

These political changes represented danger for Constantine and it seems he sought to remain aside from both Galerius and Maximian and Maxentius. Constantine married Maximian’s daughter, Fausta, in 307 but supported neither side during Galerius’ invasion of Italy. Maxentius however faced further challenges when Maximian attempted to a coup but then had to flee to safety with Constantine when this failed in April 308. To complicate matters further, the African provinces broke away from his rule and Galerius elevated Licinius to the rank of Augustus of the west on 11th November 308. Licinius controlled the European provinces of the east and, after the death of Galerius in May 311, effectively shared power with Maximinus Daza, who had previously been ‘Caesar’ under Galerius.

Maxentius’ relations with Constantine deteriorated. This was exasperated when the later seemed to make common cause with Licinius, who had captured his province of Istria in 310. Maxentius sent a general to Africa who recovered the province and made common cause with Maximinus Daza. With renewed confidence no doubt, he now declared war on Constantine in 312.

The world stage was then set with two opposing camps: Constantine and Licinius against Maxentius and Maximinus Daza.

Constantine made the first move by invading Italy from his province of Gaul and he came up against forces loyal to Maxentius for the first time at the siege of Segusio.

The Siege of Segusio – Spring 312 AD

Segusio was a heavily fortified and walled city in northern Italy. The city closed it’s gates to Constantine when he approached and the garrison remained loyal to Maxentius. Constantine ordered that the gates of the city be set alight and that the walls should be scaled. The city quickly fell and Constantine restrained his troops from plundering the spoils, instead moving on further into Italy. 

The Battle of Turin – Spring 312 AD

Fresh from his capture of Segusio, Constantine marched towards the city of Augusta Taurinorum (Turin) with his force of approximately 40,000 soldiers. As he approached the city, he encountered an army loyal to Maxentius of around 100,000 which contained a large number of heavily armoured cavalry known as ‘cataphractarii’. 

To counter the cavalry force, Constantine ordered his army to extend their frontage allowing his forces to overlap the cataphracts who attacked in a wedge formation. At this point, Constantine ordered his lightly armoured cavalry to attack the flanks of the cataphracts. He had armed them with clubs with which they unhorsed, killed or otherwise incapacitated their opponents. The cataphracts were destroyed and Constantine’s infantry then advanced destroying the demoralised enemy forces or causing them to flee. 

The citizens of Augusta Taurinorum, perhaps sensing the way the political wind was blowing, refused to admit the fleeing troops of Maxentius but opened their gates to Constantine.

Constantine moved on to Milan, which similarly welcomed him, and remained there until the middle of the summer. 

The Battle of Verona – Summer 312 AD

Maxentius sent his most senior military commander, Ruricius Pompeianus, to Verona to check the advance of Constantine. No doubt he was concerned that Milan had switched allegiance and likely was aware that other towns and cities were sending embassies to Constantine. 

Pompeianus sent a force of cavalry to check Constantine’s advance but these were defeated and routed at their camp near Brescia. Pompeianus therefore occupied the city of Verona with a large force drawn from the region of Venetia. The city itself was well fortified and naturally strong due to it’s position in a loop of the River Adige.

Constantine started a siege of the city but Pompeianus led his army outside of the walls to offer battle, where they were promptly defeated. The defeated soldiers fled back behind the walls and Pompeianus escaped the closing noose of the siege to ride out and gather a relief army. 

A short time later, Pompeianus approached the besiegers with a large army and forced Constantine to fight on two fronts. Constantine left the siege in place and led the remainder of his forces in person to fight the reinforcement army led by Pompeianus. Leading from the front, Constantine inspired his soldiers to a historic victory and emerged victorious, routing their opponents.

Pompeianus was slain on the field of battle and, seeing all was lost, the garrison at Verona surrendered shortly afterwards.

Following this victory, the cities of Etruria and Umbria declared their support for Constantine and he was therefore able to march directly toward Rome where he met Maxentius’ army at the Milvian Bridge. 

The Battle of the Milvian Bridge – 28th October 312 AD

On 28th October 312 AD Constantine advanced on Rome and fought a battle outside the city against Maxentius, who was at the time Augustus of the West. Constantine’s forces advanced, pushing back Maxentius’ men against the Tiber river until they broke. Attempting to flee, the defeated soldiers were hampered, as the only crossing was a pontoon bridge, and many were slaughtered or drowned including Maxentius. 

According to legend, Constantine had seen a vision of the ‘Chi Rho’ symbol in the sky and the phrase ‘In Hoc Signo Vinces’ (in this sign conquer), denoting God’s blessing.  

Maxentius’s body was recovered from the water and decapitated. His head was paraded through Rome and late sent to Carthage. 

Constantine was now master of the west but in the east it wasn’t until the following year that the struggle for power would be resolved between Licinius and Maximinus Daza. Maximinus Daza, perhaps with the pretentions of someone considering themselves as the senior ‘Augusti’, marched against Licinius. However he was promptly defeated at the battle of Tzirallum in Thrace, fought on 30th April 313, after which he fled to Tarsus where he conveniently died of disease a few months later. 

This left Licinius as the Augustus of the east and Constantine as Augustus of the west. 

The Battle of Cibalae – 8th October 316 AD

In 314 AD a civil war had begun between Constantine and Licinius. The conflict was caused after Constantine had found that Bassianus, who he had appointed as his Caesar, had been intriguing against his rule. Bassianus was the brother of Senecio, who in turn was a close associate of Licinius and therefore he suspected him as the motivator.

Constantine demanded that Senecio be handed over but Licinius refused. As a result Constantine marched his army into Pannonia Secunda until they met the army of Licinius outside the town of Cibalae in modern day Croatia. The date was 8th October 316 AD. Constantine was outnumbered by 15,000 men over his army of 20,000 and initially had a disadvantageous position in broken ground. He used his cavalry to screen his infantry as it advanced until they reached the plain where Licinius’ army awaited him. An intense missile exchange then preceded a attritional infantry battle which was not decided until Constantine lead a cavalry charge into the left flank of the opposing forces. Licinius’ forces were broken and suffered around 20,000 casualties but Licinius’ escaped, with his cavalry, to Sirmium and then, after collecting his family and treasury, on to Thrace.

Licinius met his further army near Adrianople and raised it’s commander, Valarius Valens, to the rank of Caesar. At the same time Licinius sought to negotiate with Constantine, however he was incensed by the elevation of Valens and this lead to a further Battle at Mardia. 

The Battle of Mardia – Unknown but late 316 AD

The date of the Battle of Mardia, between the forces of Constantine and Licinius, is unknown but believed to be late in 316 AD following the victory of Constantine at Cibalae. 

Part of the Civil Wars of the Tetrarchy (306 – 324 AD), Constantine (Augustus of the West) and Licinius (Augustus of the East) were struggling for supremacy. Licinius has recently been defeated and in raising Valerius Valens, who commanded his further army, to the rank of Augustus, had doomed his peace overtures to Constantine. 

The armies met at Mardia in Thrace, near to Harmanli in modern day Bulgaria. The battle was hard fought until Constantine sought to break the deadlock by sending a force to attack Licinius’ army in the rear. Licinius’ army managed to retreat from the battlefield in the cover of darkness and intact in no small part due to their high standard of discipline.

Constantine was victorious but the battle was not decisive. Licinius had escaped and he would eventually conclude a peace with Constantine in Serdica on 1st March 317 AD. The terms of the peace saw Constantine confirmed as senior to Licinius, his control of all European territories except Thrace and the execution of Valens.

The peace was to last for seven short years. 

The Battle of Adrianople – 3rd July 324 AD

At the confluence of the River Evros and the River Ardas, near Adrianople in Thrace on 3rd July 324 the peace between Constantine and Lucinius, representing the Eastern and Western parts of the Roman Empire ended. 

As part of the Civil Wars of the Tetrarchy (306 – 324 AD), Constantine (Augustus of the West) and Licinius (Augustus of the East) had, seven years before, made peace. However Constantine now violated the territory of Licinius by pursuing a raiding Visigothic or Sarmatian force through his territory. Licinius reacted with hostility to the incursion and Constantine, likely spoiling for a fight anyway, obliged by bringing approximately 130,000 soldiers to the field. 

Constantine’s army was outnumbered by around 35,000 men but had the advantage of experience as many troops were battle hardened. He gained the initiative by creating the impression he was going to build a bridge over a river and at the same time secretly positioning archers and cavalry in a wooded hillside. The archers and cavalry launched a surprise attack causing the opposition to withdraw to higher ground. Constantine pressed his attack, despite being wounded in the thigh, and his army caused approximately 34,000 casualties in the opposing force. His success was attributed variously to the courage and ability of Constantine personally, his soldiers discipline and skill and to the personal ‘felicitas’ of their leader. 

The battle was also notable for the use of the labarum standard being moved with it’s guard to any parts of the battle where Constantine’s army seemed to faltering.

Licinius and his forces were able to leave the battlefield and withdrew towards Byzantium, followed by the victorious Constantine.  

The Battle of the Hellespont – Unknown date in July 324 AD

The Hellespont is the narrow sea route between the Aegean Sea and the Sea of Marmara, now known as ‘The Dardanelles’. The Hellespont, separating Europe from Asia, is between 0.75 and 3.73 miles wide and 38 miles long. 

On the European shore, in 324 AD, a garrison was holding the settlement of Byzantium for Licinius (Augustus of the East) against the forces of Constantine. Licinius’ forces had early been defeated at the Battle of Adrianople on 3rd July 324 and the majority had been transported to the Asian shore.

Constantine laid siege to Byzantium but needed to control the sea crossing between the city and Asia to cut the supply to the garrison and to enable his army to reach Licinius’ forces. 

Constantine’s eldest son, Crispus had been placed in charge of the fleet in the struggle with Licinius and his navy. Crispus sailed with his fleet of around 200 ships, from the port of Piraeus in Greece, to the Hellespont. Licinius’ admiral Abantus had assembled a fleet of 350 ships and the two forces met in the narrow sea passage where Crispus’ compact squadrons was able to outmanoeuvre the larger enemy force, constricted in the narrow waters, and sink many of his vessels. 

Abantus withdrew his fleet further up the Hellespont where a further battle occurred the next day. In the interim Crispus had added more ships to his force and had the assistance of a storm which impacted the opposing fleet, wrecking many ships against the shore. 

Crispus’ victory was total with only four ships of Licinius’ fleet surviving either wrecking, destruction or capture. 

Licinius, when he learned of the destruction of his fleet, withdrew the Byzantium garrison to the Asian shore. Constantine was able to occupy the city and cross the sea to confront Licinius’ forces for a final time at the battle of Chrysopolis on 18th September 324.  

The Battle of Chrysopolis – 18th September 324 AD

Constantine’s eldest son, Crispus, had soundly defeated the fleet of Licinius at the Battle of the Hellespont in July 324. With this victory, Licinius had withdrawn his forces from Byzantium and concentrated his forces at Chrysopolis near Chalcedon. 

Constantine crossed his army to Asia and marched to confront Licinius’ forces who outnumbered his army of 105,000 by about 15,000 men. Licinius, by this point probably with good reason in light of his string of defeats, was suspicious of Constantine’s apparent divine assistance from the Christian God. He forbade his soldiers from attacking or even looking at the labarum standard of Constantine’s forces and prominently displayed banners of pagan deities in his ranks. Constantine himself apparently withdrew to his tent to seek the guidance of God prior to the battle, further reinforcing this as a clash between religions. 

The advice from God to Constantine is unknown but it did cause him to seize the initiative. Constantine’s army, apparently disregarding any advanced tactics, launched a frontal assault and routed Licinius. Licinius fled to Nicomedia but his army suffered 30,000 casualties and the rest apparently fled the field.

Licinius seemingly realised that his ‘game was up’ was persuaded to surrender himself to Constantine’s mercy with his wife Constantia (Constantine’s half-sister) acting as intermediary. Constantine accepted Licinius’s surrender but a few months later went on to break his oath and have him executed for plotting, whether this was real or imagined, against him. Licinius’ son, Licinius Junior was also put to death in 326 AD and, like his father, subject to ‘damnatio memoriae’.

The defeat of Licinius’ army and his surrender marked the end of the Civil Wars of the Tetrarchy. Constantine was now the sole ruler of the Roman Empire – the first person, since Diocletion had elevated Maximian to the status of joint Augustus in April 286 AD, to hold this singular power. 

Constantine went on to make the momentous decision to give the Roman Empire a second capital city at Byzantium, which was to be much expanded and aggrandised. He renamed the city as Constantinopolis and it would later be known as Constantinople.


Potter, David: ‘Constantine the Emperor

Stephenson, Paul: ‘Constantine: Unconquered emperor, Christian victor

James, Elizabeth: ‘Constantine the Great: Warlord of Rome

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  1. […] Constantine’s rise to sole power continued after his victory at the Milvian Bridge, become sole ruler of the Empire, and to found the city of Constantinople on the site of the Greek settlement of Byzantium. His rule saw the Edict of Milan, which gave full tolerance to Christians in the Empire, and lead to the eventual victory of Christianity as the religion of the Romans.  […]

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