To shore up the prestige and dignity of the four emperors, uniformity was the key. Each city had an imperial palace, an audience chamber and a hippodrome; each man had his own staff, court and military guard. Diocletian’s court in Nicomedia reflected the style of eastern rulers’ courts. Subjects paid homage by calling the emperor ‘lord’ and prostrating themselves before him. Under the four emperors, the signs of despotism were much more overt.6 However, there was one further, key illustration of the severe nature of the tetrarchy system. A clue lies in the new names that each of the emperors adopted to emphasize the quasi-divine basis of their authority: Diocletian was called Jovius (after the god Jupiter), and Maximian Herculius (after he of the Seven Labours). The underpinning of the new regime was emphatically ancient, traditional and pagan. But in the ointment of Diocletian’s drive for uniformity there was a fly.
The single policy of reorganization across the empire for which Diocletian is infamous is his repression of the Christians. Why were they such a threat? Throughout the history of the Roman empire, the favour of the Roman gods was central to its successful creation and survival. With the sweep of conquest, new cults and religions had come within its embrace. Cosmopolitan Rome not only tolerated new religions, but welcomed them too: just as new peoples became Roman citizens, so their religions too were incorporated into the pantheon of Roman gods. Cybele from Asia Minor, Mithras from what is today Iran, Isis and Serapis from Egypt, the goddess Tanit from Carthage – all these gods and their cults came to Rome. They were both worshipped there and took on Roman divine forms. Indeed, their acceptance in Rome meant that the cults grew in stature. The message that their incorporation sent out was clear: even the gods of Rome’s former enemies now favoured Rome. The process served to weld the loyalty of Rome’s subjects to the empire.
Yet there was a limit to this spirit of Roman toleration for new cults – a line that must never be crossed. A number of small, individual cults posed no threat to state control of religion; indeed, they seemed only to enrich it. But the formation of an organized, alternative community did.7 The Romans hated Christianity because they considered the worship of its one god dangerously exclusive. It was a rejection of everything it meant to be Roman. By refusing to pray to Roman gods, Christians rejected the Roman race and the Roman order of things. But Christianity posed an even greater threat than this. After decades of crisis, the ‘peace of the gods’, the unwritten contract by which the Roman gods presided benevolently over the empire in return for worship, was more than a highly guarded prize. On it depended the stability of the entire empire. It was essential to rebuilding security. Loyalty to a Christian God only put that security in jeopardy. Times of greatest crisis entailed the greatest clampdowns.
The first empire-wide persecution of Christians took place in 250. With the northern borders of the empire threatened by Goths, the emperor Decius called for a universal sacrifice in his honour. He wanted to assure himself of divine protection by the gods. Certificates of sacrifice were issued to every citizen, proving that they had participated in them. The Christians who refused were punished with torture and execution. The persecutions ended, but the problem did not. Forty years later, under Diocletian’s uniform regime of the four emperors, Roman control of belief was even more paramount. Tradition, discipline and respect for the old gods were the very cornerstones of Diocletian’s reforms and the empire’s renewal. There was no room for dissent. Unsurprisingly, it was only a matter of time before the tinder was lit and the problem of the Christians flared up violently once again.
In 299 Diocletian learnt of some pagan priests who had tried to divine signs of favour from the gods. When they were unable to find auspicious omens, they blamed their failure on some Christian soldiers who had made a sign of the cross. The reaction that resulted was uncompromising. Diocletian first ordered a purge of the army. After trying to root out Christianity he changed tack and attempted to stop it functioning altogether. He instructed a detachment of the Praetorian Guard in his own imperial city of Nicomedia not simply to burn the local church. Once the flames had subsided, he ordered his soldiers to set to work with axes and crowbars and level it to the ground.
An empire-wide edict followed: Christian meeting-places should be destroyed, scriptures burnt and Christians who held any office should be stripped of it. Depriving Christians of their status deprived them of their legal standing. They were thus liable to summary execution and torture. Christian freedmen were to be made slaves once more. Finally, the bishop of Nicomedia was beheaded and many others were imprisoned and tortured. By ruining Christianity, the persecutors were seeking to foster their traditional religion. In reality, however, the policy had no popular support. It served only to confirm how widespread Christianity had become, and how organized. The campaign had been a bloody, violent failure in an otherwise extraordinarily successful rule.8 Two years after their initiation, Diocletian called an end to the persecutions in 305.
In that same year Diocletian retired to his magnificent seaside palace at Spalatum (modern-day Split in Croatia), the skeleton of which is preserved today in the form of a medieval town. He was the first and only Roman emperor ever to abdicate voluntarily. His severe, authoritarian work of reform was done, and now he could enjoy the delights of the Dalmatian coast without worry. That at least was his hope. However, with his retirement, the success of the tetrarchy that he had devised began to decline.
Diocletian’s ambition was for the system not only to address the problem of security, but also to bring the destabilizing rapid turnover of emperors to an end. The appointment of two Caesars subordinate to two Augusti had made explicit and orderly the means of succession, and thus, it was hoped, would deter usurpers. For all the innovation and success of his other reforms, however, in this ambition his system was a complete failure. All it created was more intense jockeying for power, a new welter of rivalry and competition. It soon became apparent that the only thing that glued the four emperors together was the consent of the others. As soon as that was lost, the government of four would collapse like a sheaf of wheat.9
On 1 May 305, at the ceremonies of succession, the cracks were quick to appear. When the former Caesars, Constantius and Galerius, became the new Augusti and took the place of Maximian and Diocletian, one young man at the ceremony in the east had high hopes that he would be appointed as one of the new Caesars. However, it was not the name of Constantine, the son of Constantius, that Diocletian read out, but that of the newly appointed junior emperor Maximinus Daia, a tough, vehemently anti-Christian soldier from Illyria. The overlooked young Constantine had every right to seethe. Not only the son of a Caesar, he was also a man of considerable achievement in his own right. He had proved himself on the battlefield against the Persians on the eastern frontier, and in the north against the Sarmatians. After his father had been sent to Gaul and Britain, he had remained at Diocletian’s court. Here he was a high-ranking officer, but his achievement went further than that. In the snake-pit of politics and court life he had perhaps also learnt to be a clever dissimulator. That skill certainly would have been useful at the succession ceremony. However, he was not the only candidate to be unfairly overlooked.