At the western court in Milan, the same ceremony to appoint the new Caesar of the west was being held on the same day. Here Marcus Aurelius Valerius Maxentius, the son of Maximian, Augustus of the west, was passed over in favour of another able army officer called Flavius Valerius Severus. Maxentius had reason to be more than bitter at failing to make the grade. The appointment of Daia in the east had been understandable: he had connections there and was a trusted general and friend of Galerius. But as the son of Maximian, a former Augustus, surely Maxentius had a better claim than Severus to be Caesar in the west? Disappointment turned to suspicion. Severus, like Daia, was an army friend of Galerius. Did his appointment reflect something more sinister? Did the eastern Augustus have designs for control of the west too? The new appointment posed only unanswerable questions. Although the ambitious Constantine and Maxentius did not yet know it, opportunities would come their way to redress the slight they had suffered, and they would not be long in coming. The system of the tetrarchy would soon find itself in meltdown.
According to some sources, the first rift was between the two new Augusti. Constantius perhaps feared that his son would become a political hostage in the court of the eastern Augustus. What is certain is that he sent a dispatch to Galerius requesting that Constantine be allowed to join his campaigns to re-establish Roman order in Gaul and Britain. Galerius was reluctant to do so. Perhaps he also knew that he had a hold over his fellow Augustus as long as Constantius’s son was at his court in the east. Following persistent requests, Galerius relented, keeping up the appearance of harmony between the two senior rulers. However, beneath the show of cooperation, so the story goes, he had begun planning Constantine’s downfall. Galerius had instructed Severus to intercept and kill the young Constantine. A trap had been set.
Constantine quickly got wind of the plot. One night, he waited until Galerius had retired to his rooms. Then, in the small hours, he took flight. During the long journey west, he skilfully outwitted his pursuers by maiming horses, used for imperial service, which he encountered along the way. Constantine thus threw the potential assassins off the scent of his trail. He was a tall, strong, athletic man and, riding long and hard, he reached his father at Boulogne in Gaul in time to aid him in his last campaign – an expedition across the English Channel to Britain.10
The war against the Picts was a great success, and Constantine’s role in it was critical. For his valour he earned the title Britannicus Maximus (Greatest Briton). The popularity he gained with the army in Britain would prove incredibly influential to his future career. But perhaps equally influential was what he was able to witness. His father was a very different emperor from the eastern rulers, Diocletian and Galerius. Certainly, Constantius had paid lip-service to Diocletian’s edict to persecute the Christians; he had, for example, ordered the destruction of some churches. It was not in this action, however that his reputation was anchored. Rather, he was celebrated for protecting the Christians from the brutality that he had witnessed in the east. This was not out of the kindness of his heart; Constantius was a seasoned, unsentimental general from Illyria. The decision came down to a simple political judgement – he saw that persecuting Christians would not help him govern western Europe.
Unfortunately for his son, the reunion they enjoyed was brief. On 25 July 306 Constantius died prematurely at Eburacum (modern-day York). The cause of death was perhaps leukaemia, a possible clue lying in the nickname that was given to him posthumously: ‘the Pale’. There was one last, critical action that Constantius took before he died. According to Constantine, his father appointed him Augustus of the west. It was a controversial decision because Constantius had made no attempt to consult with his fellow emperors, least of all Galerius. Nonetheless, the army immediately and joyfully joined in proclaiming the popular Constantine the new Augustus of the west. With that, Diocletian’s tetrarchy was, in effect, wrecked. Constantine had broken cover.
Although Galerius, the Augustus in the east, was forced to accept Constantine’s elevation in the world, he sent him a purple robe recognizing him not as the new Augustus but as the more junior Caesar. To the position of Augustus in the west he promoted Severus. However, not even Constantine’s demotion could hide the new reality of the Roman empire. The government of the tetrarchy was nothing more than a temporary gloss. The four emperors were actually involved in a covert war, each in a bid for more power. Over the next six years that hidden war intermittently broke out into full civil war. The overlooked Maxentius was the first to make his move. He brought his father, Maximian, out of retirement, won over the Praetorian Guard in Rome and in 307 declared himself Augustus with control of Rome, Italy, Corsica, Sardinia, Sicily and North Africa. Galerius sent Severus to deal with the revolt, but Severus was unable to match the combined military forces of Maxentius and Maximian. What troops he could muster deserted him at the gates of Rome. Severus was captured, forced to abdicate power, and then executed at Tres Tabernae, outside Rome, in 307.
From his imperial palace at Trier Constantine had kept a close eye on these events. To maintain his position in a rapidly shifting balance of power, he had even made an alliance with Maxentius and his father. It was sealed by Constantine’s marriage to Fausta, Maxentius’s sister. All too soon, though, the alliance between the three men broke down in the most spectacular way. First, Maxentius was declared a tyrant and a usurper (with Constantine, Daia, Galerius and a new appointee, Licinius, agreed as the legitimate holders of power). Maximian broke away from his son, but soon, in one last throw of the dice, turned against his son-in-law too and sought to win imperial power in the west for himself. This rebellion now forced Constantine to enter the civil war for the first time. At Arles in Gaul he defeated Maximian, who promptly hanged himself. The response of Maxentius to the news of his father’s death was unequivocal. First he ordered the deification of Maximian, then he smashed down the statues and images of Constantine, the icons by which he was recognized as a legitimate emperor, and thus declared war on his former ally. He wanted, he said, revenge for the death of his father.11
In 311 Galerius died, and with him the last vestiges of the tetrarchy. The end met by this famous persecutor of the Christians was gruesomely celebrated by the historian Eusebius. Suppurating inflammations and ulcers infested the genitals of the obese emperor. His sick, lumpen body stank. The doctors who were unable to cure him were summarily executed.12 Was he being punished for his sins against the Christians? This was perhaps the conclusion drawn by Galerius himself: in his last edict, made in his final few days, he renounced the policy of Christian persecution. The tide was turning. But little did he know quite how spectacularly that reversal would soon be transformed into one of the most important revolutions in all history.
Galerius’s death left Daia and Licinius disputing control of the east. In the west, two key protagonists also walked the stage: the usurper Maxentius and his brother-in-law Constantine. Constantine was determined that the job of ruling the western half of the Roman empire fell to him alone. However, he wanted to fight on the side of legitimacy and right. His publicly stated aim was to ‘avenge the state against the tyrant and all his faction’. Indeed, his biographer and Christian panegyrist, Eusebius, described Constantine’s war as a ‘task of liberation’.13
In reality, Constantine simply wanted to eliminate his rivals. Out of the shambles of the tetrarchy, he would make his bid for sole power. From the seed of that self-interest and ambition, however, would grow one of the most significant moments in European history. The outcome of the war for the west would not only decide the fate of the Roman empire – it would alter the fate of the world.