Constantine the Great: The Years 313-315

San Lorenzo Maggiore in Milan, with a statue of Constantine in front of it.

In February of the year 313 Constantine and Licinius met in Mediolanum (Milan) in Northern Italy. There the two men formalised the alliance that had already been in effect since 311. Licinius married Constantia, Constantine’s Christian half-sister. The emperors furthermore agreed that Constantine would rule over the western half of the Roman Empire and Licinius over the eastern half. Since much of the latter half was still in the hands of Maximinus Daza, Licinius would have to deal with him first. The exact border between Constantine’s territories and those of Licinius was rather unclear, and that would later lead to conflicts. The two emperors also made a deal about freedom of religion in the whole Empire and the return of church property that had been confiscated to the Christians. This was especially important for the territories that were still controlled by Daza, who was, after all, a notorious persecutor of Christians. The agreement between Constantine and Licinius is generally known as the “Edict of Milan”, although strictly speaking it was not an edict and Licinius would promulgate it in Nicomedia, after his victory over Daza (see below).

Licinius defeats Daza

After an agreement had been reached in Mediolanum, Constantine had left for his old capital of Augusta Treverorum (Trier) while Licinius had travelled to the Balkans. The latter was in a hurry, as Maximinus Daza had crossed the Bosporus and attempted to occupy the territories of Licinius. In December of 312, Daza had issued an edict that had ended the persecution of Christians in his territories. His reasons for doing so were likely purely pragmatic. His ally Maxentius had been defeated and killed by Constantine, so Daza was now on his own. There was a serious risk that Constantine and Licinius would soon join forces and attack him. However, when he heard that his two adversaries were in Mediolanum, he decided to take swift action. Considering an attack the best defence, Daza had gathered an enormous army, which was 70,000 men strong according to Lactantius.[1] This figure is no doubt too high, but Daza’s army certainly must have been large.

Licinius vs. Maximinus Daza (source: Ancient World Mapping Center. “À-la-carte”; CC BY 4.0).

After crossing the Bosporus, Daza besieged Byzantium, which surrendered after an eleven-day siege. The capture of this important city was quite an achievement, as at the end of the second century this had taken the emperor Septimius Severus almost three years. Daza’s next target was Perinthus (also known as Heraclea), which he also captured. In the meantime Licinius had reached Hadrianopolis, a city that had been named after the emperor Hadrianus and is currently known as Edirne. Licinius and his army of 30,000 soldiers followed the road to the east while Daza and his army marched west. According to Lactantius, Daza promised to Jupiter that, in case of victory, he would wipe the name of the Christians off the face of the earth. Licinius for his part was supposedly visited in his sleep by an angel of the Lord, who commanded him to pray to the “highest god” (summus deus) with his army.[2] As was mentioned above, Licinius – a Dacian Roman – had a Christian wife, but he himself was definitely not a Christian. This makes Lactantius’ story rather dubious. Moreover, it should be noted that the term “highest god” does not necessarily refer to the God of the Christians. The Christian God was, after all, the “only god”, while a “highest god” suggests that there are other gods as well.

Statue of Constantine in Milan.

However this all may be, on 30 April the armies of Licinius and Daza clashed on a plain in Thrace that Lactantius calls the Campus Serenus. Daza’s army was much larger, but his men were exhausted from the long march in cold winter weather and the previous fighting at Byzantium and Perinthus. By contrast, Licinius’ soldiers were still fresh and easily slashed their way through the ranks of the enemy. Half of Daza’s army were butchered, the rest either surrendered or fled. Daza himself threw away his imperial robes, dressed up as a slave and made his way to Nicomedia. He could not stay there, as Licinius was hot on his heels. After collecting his wife and children, he therefore fled to Cappadocia. Meanwhile Licinius and his army had entered Bithynia and in June the emperor took Nicomedia without encountering any opposition. There, on 13 June, the emperor promulgated the aforementioned “Edict of Milan”. The sizeable Christian community of the city, which had not long ago lost its principal church and its bishop, must have been overjoyed.

Daza and his skeleton of an army had tried to entrench themselves in the Cilician passes in the Taurus mountains, much like Pescennius Niger had done 120 years previously when he was attacked by Septimius Severus. But Licinius’ troops quickly broke through the fortifications of their adversaries and Daza was forced to flee to Tarsus. In July or Augustus he died there under mysterious circumstances. The emperor must have been in his mid-forties. His death may have been a case of suicide by poison, but we cannot rule out that Daza died of natural causes.[3] In any case his death ended the war and Licinius was now in complete control of the eastern half of the Roman Empire, a part of the Empire where many Christians lived. In some areas the Christians may have already constituted the majority of the population and the “Edict of Milan” quickly led to a genuine church building boom in the east.[4] It should be noted that these projects were not stimulated by Licinius, who had other affairs to tend to.

Chief among these other affairs was getting rid of potential rivals, which was business as usual for many Roman emperors. Many of these rivals had in previous years found refuge at Daza’s court. Among them were Candidianus, who was the emperor Galerius’ adoptive son, and Severianus, son of the emperor Severus, who had been killed back in 307. Still in 313 Licinius had both men executed. Candidianus had been engaged to Daza’s seven-year-old daughter, who was also killed, together with her eight-year-old brother Maximus. Their mother, Daza’s wife, was drowned in the river Orontes. Lastly, just to be sure Licinius also got rid of Valeria, the emperor Diocletianus’ daughter and Galerius’ widow. Together with her mother Prisca, Diocletianus’ widow, Valeria managed to evade Licinius and his henchmen for fifteen months. In the end, however, the women were arrested in 315 in Thessalonica in Macedonia and subsequently decapitated.[5] There was now just one rival left for Licinius: his brother-in-law Constantine.

Constantine in Trier

The Porta Nigra in Trier.

Once he was back in Augusta Treverorum, Constantine again crossed the river Rhine for an expedition against the Franks. The campaign was a success, and the emperor subsequently celebrated his victory by throwing games at the local amphitheatre. The population of the city watched in awe as numerous Frankish prisoners were massacred in the arena. It must have been in Augusta Treverorum that Constantine was joined by his Christian mother Helena. After Constantine’s father had repudiated her around 288 she had returned to the region where she had been born, not far from Nicomedia. Now, some 25 years later, she was back at the imperial court. Around the same time the Christian orator Lactantius must have arrived there. Lactantius was originally from Roman Africa and was of Berber or Punic descent. Initially he had not been a Christian, but in Nicomedia he had converted to Christianity. Constantine soon appointed him as tutor for his adolescent son Crispus, who was now 12 or 13 years old. Lactantius would become an important, though hardly unbiased source for the life of Constantine.

Around this time Constantine must have already been in frequent contact with the bishops in his part of the Roman Empire. One of his contacts was the bishop of Rome, Pope Melchiades (311-314), and another was bishop Ossius of Corduba, who not only represented an important Christian community in Spain, but may even have accompanied Constantine on his campaign in Italy in 312.[6] Although the Christians in Spain, Gaul and Germania were still outnumbered by “pagans” by a large margin, they were much more organised. Moreover, the term “pagans” obscures the fact that the non-Christians were an extremely heterogeneous group. The degree of organisation of the Christian communities is demonstrated, for instance, by the constant exchange of letters between the bishops in the western half of the Empire. Around this time, if not earlier, Constantine must also have become acquainted with the bishops Marinus of Arelate (Arles), Reticius of Augustodunum (Autun) and Maternus of Colonia Claudia Ara Agrippinensium (Cologne) and Augusta Treverorum (Trier). Although most of the imperial retainers were still non-Christians, the Christians were quickly working their way to the top.

Statue of Constantine on the Capitol in Rome.

The Donatists

A religious conflict in the province of Africa now required Constantine’s attention. In 311 a certain Caecilianus had been elected bishop of Carthage. Like his predecessor Mensurius he represented the moderates, i.e. those who showed understanding for those Christians who during the persecutions had sacrificed or handed over sacred texts to be burned. The two bishops were not too fond of martyrs and the cults that had sprung up around them. Radical bishops, however, deposed Caecilianus and replaced him with Majorinus, who soon died and was succeeded by his fellow radical, a certain Donatus. As early as 312 Constantine had sided with Caecilianus, and he gave financial support to both the man himself and the bishops that supported him. Donatus’ supporters, the so-called Donatists, then sent a petition to the emperor, possibly in the autumn of 313, when the emperor was residing in Augusta Treverorum. In the petition they basically asked Constantine to make use of his imperial powers and remove Caecilianus from his see. If he had wanted, Constantine would have been fully within his rights to do so. A precedent had been set over forty years previously when the emperor Aurelianus, not a Christian by a mile, had deposed the patriarch of Antioch.

Constantine decided not to take a decision himself. He delegated the matter to a synod presided over by Pope Melchiades. The aforementioned bishops Marinus, Reticius and Maternus also participated in the synod, as did twenty bishops from North Africa, half of whom were supporters of Donatus. The synod reached a decision at the Lateran in October of 313, and the presence of Donatists at the meeting did not prevent it from ruling in favour of Caecilianus. The appeal against this decision was entrusted to a much larger church meeting, a council. On 1 August 314 this council met at Arelate. Pope Melchiades had been expected to preside over the meeting, in which over fifty bishops participated, but he had died before it had even started. His successor was Sylvester (314-335), who declined to travel to Arelate and sent a delegation of two priests and two deacons instead. Marinus now assumed the presidency of the council, which was logical given that it was held in his diocese. One very important decision of the council was about the date for Easter. From now on Easter was to be celebrated in the whole Roman Empire on the first Sunday after the first full moon in spring. This was an important point of contention in early Christianity.[7] Of course the appeal of the Donatists was also debated. Again all charges against Caecilianus were dismissed, a decision that was ultimately upheld by Constantine himself. In spite of all this, Donatism in North Africa did not die out until well into the sixth century.

San Giovanni in Laterano and the Lateran Palace.

Back to Rome

In 314 Constantine had continued his campaigns along the Rhine and in 315 he joined forces with Licinius for a campaign along the Danube against other Germanic tribes. On 25 July of the latter year he was expected back in Rome for the celebration of his Decennalia, his tenth year on the throne. Remarkably, Constantine had previously skipped another important event, the Ludi Saeculares, the celebration of the passing of another century. The last official Ludi Saeculares had been celebrated in May and June of the year 204 during the reign of Septimius Severus. A saeculum was originally a period of 110 years, which meant that the next celebration was set to take place in May/June of 313, the 110th year after 204. In the past the century had frequently been shortened to 100 years to match with the 800th, 900th and 1000th anniversary of the city of Rome. Claudius (in 48), Antoninus Pius (in 148) and lastly Philippus Arabs in the year 248 had all done just that. Constantine could have chosen to link up with Septimius Severus, but instead he opted to skip the Ludi Saeculares altogether. In May and June of 313 he was campaigning along the Rhine.

Basilica Nova or Basilica of Maxentius and Constantine.

Basilica Nova or Basilica of Maxentius and Constantine.

Hand of the gigantic statue of Constantine in his basilica.

For his Decennalia, on the other hand, the emperor was willing to come to the Eternal City. It was on this occasion that Constantine inaugurated a number of buildings and monuments. First of all there was the immense Basilica Nova on the Forum Romanum. The basilica is nowadays known as the Basilica of Maxentius and Constantine, but the building was in fact predominantly a work of the former. Constantine only added the finishing touch by making the entrance in the long south side of the basilica instead of the short east side. Inside the basilica a gigantic statue of the seated emperor was placed, perhaps some twelve metres high, parts of which have been preserved.[8] Constantine also opened a large complex of public baths on the Quirinal hill. Again this project had been started by Maxentius. Constantine furthermore had the Circus Maximus restored and embellished.[9] Many Romans must have remembered how during festivities organised by the emperor Diocletianus part of the Circus had collapsed, with many fatalities as a result.

In addition to these buildings the Senate and people of Rome had granted Constantine a triumphal arch next to the Colosseum. Although it was formally a gift, the emperor himself had made all the decisions about the decorations. The remarkable monument is a mix of old and new elements. There was apparently no time to make all the decorations from scratch, so Constantine incorporated reliefs and medallions into his monument that came from older monuments erected by the emperors Trajanus (98-117), Hadrianus (117-138) and Marcus Aurelius (161-180). Among the original elements are the six friezes with scenes that commemorate Constantine’s victory over Maxentius. The scenes are usually interpreted as the departure from Mediolanum, the siege of Verona, the battle of the Milvian bridge, the entry into Rome, a speech in the Forum Romanum and the distribution of money in the Circus Maximus. All decorations must have once been painted, but not a single trace of paint remains today. The arch was topped by the emperor himself in a chariot, while on the arch the emperor was hailed as liberator urbis and fundator quietis. The monument does not have any Christian elements, unless one counts the rather vague phrase instinctu divinitatis – “inspired by the deity”. Non-Christian elements are omnipresent. On the relief featuring the departure from Mediolanum we clearly see images of deities on the two army standards, commonly identified as Sol and Victoria. The former is also depicted elsewhere on the arch, in his chariot, and the latter can be seen soaring through the sky on the relief featuring the siege of Verona.

Text on the Arch of Constantine; the phrase instinctu divinitatis is in the third line.

Departure from Mediolanum.

Presumably in September Constantine returned to Augusta Treverorum. He would not stay there for long. Soon the emperor would set his sights on his brother-in-law Licinius. The two men do not seem to have got along very well. Ever since becoming emperor in 306 Constantine must have dreamed about bringing the entire Roman Empire under his control and we may assume that Licinius was hardly less ambitious. A violent clash between the two rivals was inevitable. A Roman senator named Bassianus would play a shadowy role in the whole affair. He was married to Constantine’s Christian half-sister Anastasia. The marriage had probably been arranged with Constantine’s consent, which can be seen as an attempt by the emperor to foster relations with the Roman aristocracy after his entrance in Rome in 312. Constantine had plans with Bassianus, but Licinius had plans too.

Above: Sol in his chariot; below: entry into Rome.

The Colosseum with the Arch of Constantine next to it.


Primary sources

Secondary sources

  • Adrian Goldsworthy, The Fall of the West, p. 178 and 186-189;
  • Henk Singor, Constantijn, p. 293-312;
  • Timothy Venning, A Chronology of the Roman Empire, p. 645-649.


[1] Lactantius, De mortibus persecutorum, chapter XLV.

[2] De mortibus persecutorum, chapter XLVI.

[3] Lactantius claims it was a suicide by poison, Eutropius suggests that his death was a coincidence (fortuita morte), Eusebius claims that the emperor was struck with blindness and Zosimus and Aurelius Victor simply state that Daza died in Tarsus.

[4] Henk Singor, Constantijn, p. 313.

[5] De mortibus persecutorum, chapters L-LI.

[6] Henk Singor, Constantijn, p. 261.

[7] Henk Singor, Constantijn, p. 300-301.

[8] It is possible that it was originally a statue of Jupiter or Hadrianus that was reworked to resemble Maxentius. Constantine then had it reworked again to resemble himself. See Henk Singor, Constantijn, p. 278.

[9] Mentioned in Aurelius Victor, De Caesaribus 40.

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