When the Roman Empire came close to breaking apart, and how Rome fought its way back

For more than two centuries, the Roman Empire had grown, adapted and survived. The reign of Augustus had established a new political system, later emperors had expanded and consolidated Roman territory, and generations of soldiers, merchants, administrators and farmers had helped connect an enormous world around the Mediterranean. Rome had experienced wars, rebellions, epidemics and political struggles before, but the empire had generally remained intact.

Then the third century brought a crisis unlike anything Rome had experienced before.

Between 235 and 284 CE, the Roman Empire went through a period of extraordinary political instability. Emperors rose and fell with alarming speed. Soldiers increasingly decided who would become emperor. Civil wars weakened the frontiers. Foreign powers attacked Roman territory. Economic difficulties affected trade and taxation. Several regions temporarily separated from the central government.

For a time, it appeared possible that the Roman Empire might actually break apart.

The crisis did not begin because of one single event. It developed from several problems that had been building over generations. The empire had become enormous, and maintaining its borders required enormous military resources. The Roman army was spread across thousands of kilometres of frontier. The empire also faced powerful external rivals, particularly the Sasanian Persian Empire in the east, while Germanic and other peoples placed increasing pressure on the northern frontiers.

At the same time, political competition inside the empire had become increasingly dangerous.

The Roman emperor was the central figure in the imperial system, but the emperor's authority depended heavily on military support. An ambitious general with a loyal army could challenge the emperor and claim the throne. Soldiers often supported commanders who promised better pay, rewards or political advantages.

This created a dangerous cycle.

A general could become emperor because his army supported him. Another general could then challenge him with another army. Civil war weakened the empire, and the weakened empire became more vulnerable to external enemies. The need for more soldiers and greater military spending placed additional pressure on the state.

In 235 CE, the emperor Severus Alexander was killed by his own troops. His death marked the beginning of a period in which emperors were often proclaimed by armies in the provinces rather than peacefully succeeding one another through established arrangements.

The man who replaced him was Maximinus Thrax.

Maximinus was a military commander whose rise reflected the increasing importance of the army. He spent much of his reign campaigning along the Rhine frontier. His government required substantial financial resources, and taxation became an increasingly important source of tension.

Maximinus was eventually challenged by opponents in Africa and Italy. His reign lasted only a few years.

What followed was a pattern that would repeat itself.

Emperors appeared, gained military support, fought rivals and then disappeared through assassination or defeat.

The political instability was not simply a matter of incompetent rulers. The Roman political system itself had developed a structural problem. There was no simple, universally accepted method for deciding who should become emperor when an emperor died without a clear successor.

The Senate could recognize rulers, but the army increasingly had the power to make emperors.

This created a political world in which military commanders became potential candidates for supreme power.

During the middle decades of the third century, the empire experienced repeated civil wars. Some emperors ruled only briefly. Others managed to survive for several years but spent much of their reign fighting rivals.

The consequences were serious.

An emperor who had to fight a civil war could not devote all of his resources to the frontiers. Soldiers who might otherwise have defended the empire were instead fighting other Roman soldiers. Provinces could become battlegrounds, and local populations could suffer from requisitions, destruction and disruption.

At the same time, Rome faced increasingly serious external threats.

In the east, a new Persian power had emerged.

The Sasanian Empire replaced the Parthian Arsacid dynasty in the early third century. Ardashir I established the Sasanian state and created a powerful empire centered in Iran and Mesopotamia.

The Sasanians were not simply another group of raiders along the Roman frontier. They were the rulers of a sophisticated and centralized state with its own administrative traditions, military capabilities and imperial ambitions.

The rivalry between Rome and Persia became one of the most important geopolitical conflicts of late antiquity.

Sasanian armies attacked Roman territories in Mesopotamia and Syria. Roman emperors responded with military campaigns of their own.

The eastern frontier therefore became a major drain on Roman resources.

One of the most dramatic events occurred during the reign of the emperor Valerian.

In 260 CE, Valerian was captured by the Sasanian king Shapur I after a battle near Edessa. The capture of a Roman emperor by a foreign ruler was an extraordinary humiliation for the Roman state.

Shapur celebrated his victories through inscriptions and monumental reliefs that depicted Roman emperors submitting to Persian power.

For Rome, the crisis was becoming increasingly serious.

But the empire was also under pressure in the west and north.

Groups described by Roman writers as Goths and other peoples crossed the Danube and Black Sea regions, raiding Roman territory. The term "barbarian" was a Roman description for peoples outside the Roman cultural and political world, not a precise description of a single unified group.

These communities were diverse.

Some migrated, some raided, some traded with Rome, and some eventually entered Roman territory as allies or settlers. Roman relations with these groups could involve warfare, diplomacy, recruitment and negotiation.

The third century was therefore not simply a story of barbarians attacking a passive Roman civilization.

The frontier was a zone of constant interaction.

Roman armies sometimes invaded territories beyond the frontier. Foreign groups sometimes entered Roman lands. Some became Roman soldiers. Some settled inside the empire. Some fought Rome while others cooperated with Roman authorities.

The distinction between Roman and non-Roman could change over time.

Yet the military pressure was real.

Roman cities and provinces in the Balkans, Greece, Asia Minor and the Near East experienced attacks and instability. In some regions, local communities had to defend themselves when central imperial authority was weak.

The political crisis became so severe that parts of the empire temporarily developed their own governments.

One of the most important examples was the Gallic Empire.

In the late 260s, Postumus established a separate imperial regime in the western provinces. It included territories in Gaul, Britain and parts of the western empire. Postumus and his successors maintained their own armies, administration and political institutions while claiming to represent Roman imperial authority.

At almost the same time, the eastern provinces came under the influence of the Palmyrene Empire.

Palmyra was a wealthy city located in the Syrian desert. Its prosperity came partly from its position along trade routes connecting the Roman world with Mesopotamia and regions farther east.

The ruler most closely associated with Palmyra's expansion was Queen Zenobia.

Zenobia ruled on behalf of her young son, Vaballathus, and during the crisis she expanded Palmyrene control across large parts of the eastern Roman world. Her forces occupied Egypt and much of Roman Syria and Asia Minor.

The situation was extraordinary.

The Roman Empire had not formally disappeared, but central authority had weakened so dramatically that regional rulers could establish their own imperial structures.

For a time, the Roman world was effectively divided into several competing political systems.

Rome itself was not helpless.

The emperor Aurelian came to power in 270 CE and began one of the most remarkable efforts to reunify the empire.

Aurelian was a highly capable military ruler, and his reign demonstrated that the Roman state still possessed enormous resources when effective leadership could mobilize them.

He first dealt with threats in the Balkans and then turned against the Palmyrene regime.

Aurelian defeated Palmyrene forces and captured Palmyra. Zenobia was eventually taken prisoner. The eastern territories were brought back under Roman control.

Aurelian then turned west.

The Gallic Empire had existed for roughly a decade, but Aurelian's campaigns brought its territories back under imperial authority.

By 274 CE, the Roman Empire had been reunited.

Aurelian had achieved something that had seemed almost impossible only a few years earlier.

The empire was whole again.

Yet reunification did not mean that the crisis had disappeared.

The political system needed deeper reform.

Aurelian understood that the empire required stronger central authority, but he was assassinated in 275 CE before he could fully consolidate his achievements.

Another emperor, Probus, continued military campaigns and achieved important victories, but he too was killed by his own soldiers in 282 CE.

The pattern remained.

Military power could create emperors, but it could also destroy them.

Then, in 284 CE, another military commander rose to power.

His name was Diocletian.

Diocletian's reign marked a fundamental turning point in Roman history.

Unlike many of the emperors who had ruled during the crisis, Diocletian did not attempt to govern the enormous empire entirely through the traditional arrangements of the early Principate.

He believed the empire needed a new structure.

He also understood that the empire's problems were too large for one ruler to manage effectively.

The answer was a system known as the Tetrarchy.

The word means "rule by four."

Diocletian established a system in which two senior emperors, known as Augusti, governed different parts of the empire, while two junior emperors, known as Caesars, assisted them and were expected to succeed them.

The empire was not formally divided into four independent countries.

Instead, it was organized under multiple rulers who were supposed to cooperate.

This was a major departure from the political system created by Augustus.

The Tetrarchy recognized a practical reality. The Roman Empire had become so large that one emperor could not easily respond to threats on every frontier.

A ruler stationed in the east could respond quickly to Persian attacks. A ruler in the west could deal with problems along the Rhine or Danube. Another could be responsible for the Balkans or other strategic regions.

The system also attempted to solve the succession problem.

Instead of waiting for an emperor to die and then allowing competing generals to fight for the throne, the Tetrarchy was designed to provide an orderly process of succession.

The senior emperors would eventually retire or die, and the Caesars would replace them.

It was an ambitious attempt to prevent another generation of civil wars.

Diocletian also reorganized the administration of the empire.

The number of provinces increased, making them smaller and easier to administer. Several provinces were grouped into larger administrative units known as dioceses. These were then organized into broader regional structures.

The empire developed a much more elaborate bureaucracy.

Government officials became increasingly important. Tax collection was reorganized. Military administration became more systematic. The emperor's court became more formal and ceremonial.

This transformation changed the character of Roman government.

The emperor was no longer presented primarily as the leading citizen of the Republic.

The imperial court became more distant and elaborate.

Diocletian adopted ceremonial practices that emphasized the extraordinary status of the emperor. Subjects approached the ruler according to formal court rituals.

This was partly political theater, but it reflected a genuine transformation.

The emperor was now increasingly presented as an absolute ruler whose authority stood above ordinary citizens.

The political culture of the Roman Empire had changed dramatically since Augustus.

The old Republican traditions had not completely disappeared, but they had become much less central to the actual operation of imperial government.

Economic problems also required attention.

The third century had experienced monetary instability. Roman coins had been repeatedly reduced in precious metal content, and the government faced enormous expenses because of military campaigns.

Inflation became a serious concern.

Diocletian attempted to address the problem through monetary reforms and a famous price edict issued in 301 CE. The Edict on Maximum Prices attempted to establish maximum prices for a very large range of goods and services.

The policy demonstrates how seriously the government viewed inflation, although its effectiveness and enforcement were limited.

The state also needed reliable taxation.

The empire's military forces were expensive, and the bureaucracy required resources. Taxes increasingly became organized around land and agricultural production.

This placed heavy responsibilities on farming communities.

The Roman economy remained productive, but the relationship between ordinary people and the state was becoming more demanding.

The empire's transformation also affected religion.

Diocletian's reign is associated with the most systematic persecution of Christians in the Roman Empire.

Beginning in 303 CE, a series of measures targeted Christian churches, scriptures, clergy and worship. The intensity of enforcement varied across regions and over time.

These persecutions are important because they demonstrate that Christianity had become sufficiently widespread to be viewed by the imperial government as a significant issue.

Yet the persecution did not destroy Christianity.

Instead, Christianity continued to grow.

Only a few years later, the Roman imperial policy toward Christianity would change dramatically.

The person responsible would be Constantine.

Constantine was a military commander who emerged during another period of civil conflict following the weakening of the Tetrarchic system.

In 312 CE, Constantine fought his rival Maxentius at the Battle of the Milvian Bridge near Rome.

According to Christian accounts written after the event, Constantine experienced a religious vision before the battle and adopted Christian symbols. The exact historical circumstances surrounding his conversion remain debated, but there is no doubt that Constantine later became a major supporter of Christianity.

After his victory, Constantine became one of the most powerful rulers in the Roman world.

In 313 CE, Constantine and Licinius issued what is commonly known as the Edict of Milan, establishing a policy of religious toleration and allowing Christians to practice their faith openly. It did not make Christianity the official religion of the empire, but it represented a major change from the persecution associated with Diocletian's reign.

Constantine also supported Christian institutions and became deeply involved in religious affairs.

In 325 CE, he called the Council of Nicaea, a major gathering of Christian bishops that addressed theological disputes, particularly the controversy surrounding Arius and the nature of Christ.

The council did not instantly end all disagreement, but it demonstrated how closely imperial power and Christian institutions were becoming connected.

Constantine also founded a new imperial capital.

On the site of the Greek city of Byzantium, he established Constantinople, which was inaugurated in 330 CE.

The city's location was strategically important.

It stood between Europe and Asia, near the Bosporus and close to major trade routes. It was also positioned near the empire's eastern frontier and could serve as an effective center of government.

Constantinople would eventually become one of the greatest cities of the medieval world.

The transformation of the Roman Empire was now unmistakable.

The political system of Augustus had evolved into a more centralized and bureaucratic monarchy.

The army had grown in importance.

The provinces had been reorganized.

The imperial court had become more elaborate.

Christianity had moved from a persecuted minority religion toward an increasingly influential institution.

The empire itself had survived the crisis.

But it was no longer the same empire that had existed two centuries earlier.

The Crisis of the Third Century therefore should not be remembered simply as the moment when Rome almost collapsed.

It was also the period in which Rome changed.

The old imperial system had proved unable to handle the pressures of the third century without major disruption. Yet the Roman state demonstrated remarkable resilience. Aurelian reunited the empire. Diocletian reorganized its administration. Constantine transformed its religious and political landscape.

The Roman Empire had survived, but survival had come through transformation.

The crisis also changed the relationship between the emperor and the people.

Under Augustus, the emperor had carefully presented himself as the first citizen within a restored Republican system. By the time of Diocletian and Constantine, the emperor was increasingly presented as a distant and sacred ruler surrounded by elaborate ceremony.

The political world of Rome had moved a long way from the Republic.

The empire's geography had changed as well.

Rome remained symbolically important, but the emperor no longer needed to govern primarily from the city of Rome. Military and political centers had developed throughout the empire. Constantinople would become especially important, but other cities such as Antioch, Alexandria, Milan and Trier also played major roles in imperial government.

The Mediterranean remained central, but the political center of gravity was increasingly shifting toward the eastern Mediterranean and the Balkans.

The empire was becoming more diverse, more bureaucratic and more centralized.

It was also becoming increasingly Christian.

Yet Christianity was not the only religious tradition in the empire, and the transition was not immediate. Traditional Roman religions continued to exist for generations. Different Christian groups disagreed with one another. Jewish communities remained important. Religious change was gradual and uneven.

The fourth century would therefore be a period of enormous transformation.

The Roman Empire would continue to exist for centuries, but the world of Constantine would look very different from the world of Augustus.

The crisis had revealed that Rome could no longer govern its vast territories exactly as it had during the early empire.

The empire had survived by becoming something new.

But another great question remained.

Could this transformed empire remain united?

The answer would become increasingly complicated.

The Roman world would eventually develop separate political centers in the eastern and western Mediterranean. Christianity would become deeply connected with imperial power. Germanic peoples would become increasingly important within Roman armies and territories. The western provinces would face new military and economic pressures.

The story of Rome was moving toward another great transformation.

The empire had survived the crisis of the third century.

Now it would enter the age of Constantine, Christianity and the division of the Roman world.