Crisis & Recovery

1. The End of the Pax Romana and the Severan Dynasty (AD 180–235)

With the accession of Commodus (AD 180–192), the good fortune of the empire ebbed. Commodus, a megalomaniac who fought as a gladiator, was strangled in AD 192, and civil war followed. From it emerged Septimius Severus (AD 193–211), an African-born general who founded the Severan dynasty and ruled as a military autocrat, strengthening the army and the frontiers (including in Britain, where he campaigned in Scotland). His successors — Caracalla (who by the Constitutio Antoniniana of AD 212 granted Roman citizenship to all free inhabitants of the empire), Elagabalus and Alexander Severus — presided over growing chaos. In AD 235 Alexander Severus was murdered by his mutinous troops, and there began the period known as the Crisis of the Third Century (World History Encyclopedia, "Severan Dynasty," worldhistory.org/Severan_Dynasty/).

2. The Crisis of the Third Century (AD 235–284)

For nearly fifty years the Roman Empire came close to dissolution. A rapid succession of soldier-emperors — many reigning only months before overthrow or murder — rose and fell as the legions acclaimed and discarded their commanders: it is estimated that more than twenty emperors and countless usurpers ruled (or claimed to rule) between 235 and 284. The empire was wracked by civil war, by devastating barbarian invasions (the Franks and Alamanni crossing the Rhine, the Goths and other peoples raiding the Balkans and even the Aegean; the Goths sacked Athens in AD 267), and by the rise of a powerful new enemy in the east, the Sasanian Persian Empire, which captured the Roman emperor Valerian in AD 260. For a time the empire broke apart: the Gallic Empire in the west and the Palmyrene Empire of Queen Zenobia in the east briefly divided the Roman world before being reconquered. The economy collapsed under inflation and the debasement of the coinage; plague (the Plague of Cyprian) swept the population; and confidence in the old Roman order drained away. It was the most serious crisis the empire had ever faced — and, remarkably, it recovered (World History Encyclopedia, "Crisis of the Third Century," worldhistory.org/Crisis_of_the_Third_Century/).

3. The Soldier-Emperors and the Restorers

Amid the chaos, a series of energetic Illyrian (Balkan) soldier-emperors began to restore order: Claudius II Gothicus (AD 268–270) defeated the Goths; his successor Aurelian (AD 270–275), the restitutor orbis ("restorer of the world"), reconquered the Gallic and Palmyrene breakaways, defeated the barbarians, and built the great Aurelian Walls around Rome. Probus and Carus continued the work. But the fundamental problems — the succession and the threat of an unmanageable empire — remained, and they demanded a radical solution. It came with Diocletian, proclaimed emperor in AD 284 (World History Encyclopedia, "Aurelian," worldhistory.org/aurelian/).

4. Diocletian and the Tetrarchy (AD 284–305)

Diocletian (r. AD 284–305) carried out the most thorough reform of the Roman state since Augustus, and in doing so ended the Principate and inaugurated the Dominate. Judging the empire too large and troubled for one man, he divided it in AD 286 into a western and an eastern half, ruling the east himself and giving the west to his colleague Maximian; and in AD 293 he expanded this into the Tetrarchy ("rule of four") — two senior emperors (Augusti) and two junior emperors (Caesares) — to secure both administration and succession. The emperor became an absolute monarch, adopting the divine Eastern trappings of a court (prostration, the diadem, the title dominus, "lord") — the "Dominate" in which the old republican forms were finally discarded. Diocletian also reorganised the provinces (more than doubling their number), reformed the army and the tax system, and tried, by the Edict on Maximum Prices (AD 301), to halt inflation. He persecuted the Christians in the "Great Persecution" (AD 303–305), the last and largest state persecution of the faith, intended to restore the old gods. In AD 305 Diocletian — uniquely — abdicated, retiring to his palace at Split, expecting his system to continue. It did not: the Tetrarchy promptly collapsed into civil war, out of which one man, Constantine, emerged victorious (World History Encyclopedia, "Diocletian," worldhistory.org/Diocletian/).

5. The Rise of Constantine (AD 306–324)

Constantine (c. AD 272–337) was the son of the western Caesar Constantius Chlorus, and was acclaimed emperor by his father’s troops at York in Britannia in AD 306. Over the next eighteen years he fought his way to sole power, defeating his rivals Maxentius, Licinius and others in a series of civil wars. At the Battle of the Milvian Bridge, just outside Rome, in October AD 312, Constantine defeated Maxentius — and, according to the tradition preserved by Eusebius (and to Constantine himself), before the battle he saw a vision of the Chi-Rho (the symbol of Christ) in the sky, with the words "In hoc signo vinces" ("in this sign you will conquer"), and adopted the Christian symbol on his standards. In AD 313, with his co-emperor Licinius, he issued the Edict of Milan, which granted religious tolerance to Christianity throughout the empire — ending the persecutions. After defeating Licinius in AD 324, Constantine reunited the whole empire under himself, the first Christian emperor (World History Encyclopedia, "Constantine I," worldhistory.org/Constantine_I/).

6. Constantinople and the Christian Empire (AD 324–337)

Constantine’s two great acts transformed the ancient world. First, he founded a new imperial capital: on the site of the old Greek city of Byzantium, on the Bosporus, he built Constantinople (“Constantine’s city,” the "New Rome"), dedicated in AD 330 — a Christian capital at the crossroads of Europe and Asia, which for a thousand years after would be the greatest city of Christendom. Second, he used his power to advance Christianity: he endowed the church, built great basilicas (including St. Peter’s in Rome and the Holy Sepulchre in Jerusalem), summoned the Council of Nicaea (AD 325) to settle the Arian controversy and define the creed, and made Christianity, already ascendant, the favoured religion of the empire. Baptised on his deathbed, Constantine died in AD 337, leaving to his sons and successors an empire that was Christian, reorganised, and permanently divided in practice between the Latin west and the Greek east — the stage on which the final act of Roman history, the slow decline and fall of the western empire, would be played (World History Encyclopedia, "Constantinople," worldhistory.org/Constantinople/).

6b. The Plagues and Demographic Collapse

The Crisis of the Third Century was compounded, and in large part driven, by terrible epidemics. The first and most devastating was the Antonine Plague (probably smallpox), brought back by soldiers returning from the war against Parthia in AD 165–166 under Marcus Aurelius; over the following two decades it killed perhaps a quarter or more of the empire’s population, emptying cities, weakening the army and devastating the countryside. The second great infection, the Plague of Cyprian (named for the bishop of Carthage who described it), struck around AD 249–270, at the very height of the third-century crisis, and again killed enormous numbers. These plagues, coming atop constant war and invasion, caused a demographic collapse that shrank the tax base, reduced the army’s manpower, emptied the land and undermined the economy — and they were, in turn, fed by the breakdown of trade, sanitation and administration. The consequence was a self-reinforcing spiral of decline that only the draconian reorganisations of Diocletian and the recovery of the following decades could begin to reverse. The plagues stand as a reminder that the fate of empires is shaped not only by men and armies but by invisible biological forces beyond any ruler’s control (World History Encyclopedia, "Antonine Plague," worldhistory.org/Antonine_Plague/).

6c. Diocletian’s Reforms in Detail — Provinces, Army, Taxation and Price Controls

Diocletian’s reforms, taken together, amounted to a fundamental overhaul of the Roman state — the creation of the "Dominate." He more than doubled the number of provinces (to about 100), grouping them into larger dioceses under vicarii (vicars), in order to break the power of any single governor and improve administration. He reorganised the army, increasing its total strength and dividing it between the frontier troops (the limitanei) and a mobile field army (the comitatenses) held as a strategic reserve. He reformed the taxation through the census — assessing land and labour systematically (the iugatio and capitatio) — to fund the enlarged state, and he tied many people to their occupations (a precursor of the medieval order) to secure the supply of food and labour. To combat the rampant inflation caused by the debased coinage, he issued new coins and, in AD 301, the Edict on Maximum Prices, which fixed maximum prices for goods and services — a measure that failed in practice (black markets and shortages) but shows the emperor’s determination to control the economy by decree. Finally, he rebuilt and strengthened the frontier defences and adopted the court ceremonials of an eastern sovereign. These reforms, though harsh and in some respects counterproductive, restored the empire’s strength for the century and a half it needed to survive — and they set the pattern of the late Roman and Byzantine state (World History Encyclopedia, "Diocletian," worldhistory.org/Diocletian/).

6d. The Great Persecution and the Church of the Martyrs

The last and greatest persecution of Christianity was the Great Persecution decreed by Diocletian in AD 303 and continued by his Caesar Galerius. Seeking to restore the old gods and the unity of the empire, Diocletian ordered the destruction of churches, the confiscation of Christian scriptures and property, and the coercion or execution of clergy; a fourth edict required all to sacrifice to the gods on pain of death. Across the empire, thousands of Christians suffered — some, the "traditors" (those who handed over the scriptures), lapsed, but many were martyred, and the faithful survived in hiding and in the underground (the catacombs of Rome, where the church is buried, bear witness to the age of persecution). The persecution was inconsistent — in the west it lapsed early under Constantius Chlorus — and it failed utterly to uproot the church; indeed, the defiant courage of the martyrs (whose stories filled the early "acts of the martyrs") converted many and gave the church some of its most honoured saints. In AD 311, on his deathbed, Galerius issued an edict of toleration, and two years later Constantine and Licinius issued the Edict of Milan (AD 313), granting full tolerance — a decisive turning point after which Christianity, once persecuted, rose so rapidly that within a lifetime it became the official religion of the Roman state. The age of the martyrs was over; the age of the Christian empire had begun (World History Encyclopedia, "Diocletian," worldhistory.org/Diocletian/).

7. Selected Sources & Further Reading

In this sign you will conquer.— the vision reported by Constantine before the Battle of the Milvian Bridge (recorded by Eusebius and Lactantius)