Diocletian

Diocletian was Roman emperor from 284 to 305. A soldier of humble origins from the Balkans, he ended half a century of civil wars, invasions and short-lived emperors known as the Crisis of the Third Century, and rebuilt the Roman state on new lines: he shared power among four rulers, reorganised the provinces, enlarged the army and overhauled taxation. He also launched the last and harshest persecution of Christians, and in 305 became the first Roman emperor to give up the throne voluntarily.

Diocletian was born around 244, though the year is uncertain, in Dalmatia, on the Adriatic coast of modern Croatia, probably at or near the city of Salona. His family was of low status; hostile later writers said his father was a scribe or a freed slave. His original name was Diocles. Like many soldiers from the Danube and Balkan provinces, who supplied most of the empire's commanders and emperors in this period, he made his career in the army, and by the early 280s he commanded the cavalry of the imperial bodyguard under the emperor Carus.

He lived through the worst years of the third-century crisis. Between 235 and 284 more than twenty men were recognised as emperor, most of them killed by their own troops; the frontiers were broken by Goths, Franks and Alamanni; the Sasanian Empire captured an emperor, Valerian, in 260; and for a time the empire split into three. The coinage collapsed into near-worthless bronze washed with silver.

In 283 Carus died during a campaign in Persia, reportedly struck by lightning, and his younger son Numerian led the army home. In November 284, near Nicomedia (modern İzmit in Turkey), Numerian was found dead in his litter. The army chose Diocles as emperor, and he at once accused the praetorian prefect Aper of the murder and killed him with his own sword in front of the troops. Taking the name Gaius Aurelius Valerius Diocletianus, he marched west against Carus's elder son, Carinus. In 285 the two armies met at the river Margus, in modern Serbia. The battle seems to have been going Carinus's way when he was killed by his own officers, leaving Diocletian sole ruler.

Diocletian recognised that one man could no longer defend frontiers stretching from Britain to Mesopotamia while also guarding against rebellion. In 285 he made a fellow officer, Maximian, his deputy, and in 286 raised him to the rank of Augustus to govern the West, while Diocletian kept the East and the senior position. The two linked themselves to the gods, Diocletian taking the name Jovius after Jupiter and Maximian Herculius after Hercules. In 293 each Augustus took a junior partner with the title of Caesar: Constantius, father of Constantine, in the West, and Galerius in the East. Modern historians call this system of four rulers the Tetrarchy. The emperors based themselves near the frontiers, at cities such as Nicomedia, Trier, Sirmium and Milan, and Rome itself, which Diocletian seems to have visited only rarely, ceased to be the practical centre of government.

The arrangement worked. Constantius recovered Britain from the breakaway regime of Carausius and his successor, Diocletian crushed a revolt in Egypt in 297 and 298, taking Alexandria after a long siege, and the Danube and Rhine frontiers were stabilised. In the East, after a heavy defeat in 297, Galerius routed the Persian king Narseh in Armenia in 298, capturing his family and treasure, and then took the capital, Ctesiphon. The Peace of Nisibis, in 299, gave Rome territory beyond the Tigris and secured the eastern frontier for decades.

Diocletian's reforms transformed the empire's government. He roughly doubled the number of provinces, to about a hundred, making each smaller and easier to supervise, and grouped them into twelve larger units called dioceses. Civil and military authority, often combined before, were increasingly separated, so that no governor could easily command an army and launch a bid for the throne. The army was enlarged, perhaps substantially, and the bureaucracy grew to staff the new structure. Court ceremony became more elaborate: subjects approaching the emperor had to prostrate themselves and kiss the hem of his robe, and he appeared as a remote figure close to the divine.

To pay for all this, Diocletian introduced a regular system of taxation based on periodic censuses of land and people, which allowed the state to plan its budget in advance. He reformed the coinage, issuing new gold and silver coins, but inflation continued. In 301 he issued the Edict on Maximum Prices, fixing the highest legal price for more than a thousand goods and services under threat of death. It failed, since goods vanished from the markets, and it was soon ignored, but the fragments of its text found in many cities are a valuable source for the ancient economy.

Diocletian was a traditionalist who believed that the safety of the empire depended on the favour of the old gods. In 302 he ordered the persecution of the Manichaeans, a religion of Persian origin. In February 303, apparently urged on by Galerius, he issued the first of a series of edicts against the Christians, ordering churches to be destroyed, scriptures burned and Christians removed from office. Later edicts required the arrest of clergy and finally that everyone in the empire sacrifice to the gods. The persecution was enforced unevenly: harshly in the East and in North Africa, lightly in the West under Constantius. Thousands are thought to have died, though no reliable figure exists. It ended in failure, with Galerius issuing an edict of toleration in 311, and within a few years Constantine had made Christianity the favoured religion of the empire. Much of what is known about these years comes from the Christian writers Lactantius and Eusebius, who were understandably hostile to Diocletian.

In late 303 Diocletian celebrated twenty years of rule in Rome, where the great baths that bear his name were being built. Soon afterwards he fell seriously ill. On 1 May 305, at a ceremony outside Nicomedia, he abdicated, and Maximian, reluctantly, did the same in Milan. Constantius and Galerius became the new Augusti, with two new Caesars chosen to pass over the emperors' own sons. The plan for an orderly succession quickly broke down: Constantine and Maxentius, son of Maximian, claimed power, and years of civil war followed.

Diocletian retired to the vast fortified palace he had built near Salona, on the coast of Dalmatia. In 308, when he was invited to resume power to settle the conflicts, he is said to have replied that if his colleagues could see the cabbages he had grown with his own hands, they would not ask him to give them up for power. He died at the palace around 311, though the date is disputed, with some sources placing it as late as 316. In the Middle Ages the inhabitants of Salona took refuge within the palace walls, and its remains form the heart of the old town of Split. His mausoleum there became the city's cathedral, dedicated to a Christian martyr of his own persecution.

Diocletian's reforms laid the foundations of the late Roman state, which, as continued and adapted by Constantine, held together for another century and a half in the West and far longer in the East, in the form of the Byzantine Empire. The Tetrarchy itself did not survive him, but the division of the Roman Empire into eastern and western halves, which he had made routine, became permanent after 395.