What were the causes of the 3rd century crisis in the Roman Empire?

Bust of Emperor Alexander Severus

The Third Century Crisis in the 2nd century AD was a series of military, social, and political crises that almost destroyed the Roman Empire. For some fifty years (235-285 AD), one of the world’s greatest Empire’s and one of the most influential state’s in history was stricken by military revolts, barbarian invasions, economic collapse, plague, and political divisions. For many years it seemed that the Roman Empire would fragment and collapse.

However, a series of military Emperors managed to save the state and allowed it to continue to exist in the west for almost two hundred years and in the east for another thousand years. The origins of the Third Century Crisis is complex. It will be argued that the crisis was a result of, a breakdown in army discipline, barbarian invasions, the rise of the Sassanian Empire, and natural disasters.

The Background

In 200 AD, the Roman Empire was at its greatest extent since the reign of Trajan and a strong Emperor, Septimius Severus governed it. The Empire seemed invincible, and it had overawed the German and Iranian tribes on its Rhine and Danuban frontiers.[1] The Parthian Empire, once Rome’s most formidable enemy in the east was no longer a serious threat. The local elites in the Empire had become Romanized and were very loyal to Rome.

However, beneath the surface, the state had been undermined by a series of problems. Inflation as a result of the debasing of the currency was causing persistent economic issues.[2] Moreover, the plague that had ravaged Rome and its provinces in the 160s had led to a dramatic drop in the population, and this was to have long-term consequences for the Imperial territories.

After the death of Emperor Severus, his sons Geta and Caracalla ruled as co-Emperors. Caracalla murdered his brother and became sole ruler and according to Gibbon he ‘was the common enemy of mankind.’[3] After Caracalla was assassinated, in 217 AD, he was succeeded by an alleged relative Elagabalus, a former priest in a sun-cult in Syria. The sources are all hostile to Elagabalus who it is said tried to impose his religion on Rome and who may have been a transsexual.[4] When he was assassinated (222 AD) he was succeeded by his nephew Alexander Severus, who was a benign ruler who was prepared to cooperate with the Senate. However, he too was assassinated, and his death is widely seen as the start of the Third Century Crisis.[5]

The Third Century Crisis

Alexander Severus had been assassinated because he tried to buy off German invaders and the army was repelled by this and Macrinus the Praetorian Prefect became Emperor in 235 AD. The military situation on the Rhine and the Danube was very serious as more and more German tribes invaded Roman provinces. In 238 AD Macrinus was deposed in a coup and five more Emperors ascended the throne before they too were assassinated, all in the space of 12 months.[6] The Empire was battled over by a series of military adventurers or warlords, who would temporarily gain the throne before being assassinated. There was no central government and the army had become fractured and instead of battling the many barbarians they would engage in countless civil wars. This greatly weakened the once mighty Roman legions and placed a considerable burden on the citizenry.

Moreover, the Praetorian Guard the bodyguards of the Emperor often assassinate their master, out of political expediency or sheer greed. For a brief period, Emperor Philip managed to stabilize the situation. However, his assassination marked a new and even darker period in the crisis. Decius succeeded Phillip and he had to deal with a Gothic invasion. He was defeated and killed at the Battle of Abrittus (251 AD). Every year there was a series of barbarian invasions, which would ravage entire provinces. To compound the situation the Parthians in the east were replaced by the Sassanian Empire. They were to prove to be even more formidable enemies of Rome. The Sassanian monarch defeated several Roman armies and even captured Emperor Valerian and his entire army. The apparent failure of the Roman government and army to defend the provinces lead to growing separatism in the provinces and this led to the fragmentation of the Empire. By 268, the empire had split into rival states. Much of western Europe was part of the Gallic Empire. In the east, the great city of Palmyra under Odaenathus had driven back the Persians and created the so-called Palmyrene Empire, which was later ruled by the legendary Queen Zenobia.[7]

Emperor Decius who was defeated and killed by the Goths

Furthermore, parts of Dacia and the Rhine provinces were occupied by German tribes. No part of the Empire was safe from raiders and even Athens was besieged by Gothic pirates. During the many wars and invasions, pan-Mediterranean trade was severely curtailed. Hyper-inflation became the norm. Agriculture was disrupted, and food shortages were common and another eruption of the plague devasted many urban centers. However, the Empire managed to pull itself back from the abyss under a series of military Emperors. The Roman army remained very formidable and under several Illyrian Emperors, order was restored in the provinces, and the frontiers secured.

The recovery began when Claudius II defeated a Gothic invasion and after he died of the plague he was succeeded by his Master of Cavalry, Aurelian in 275 AD. He was a brilliant commander and he defeated several barbarian invasions. He then went on to defeat the Gallic and Palmyrene Empire. However, instability continued after his assassination and it was only with the accession of Diocletian, that the crisis was finally ended. However, it is widely held that the Third Century Crisis permanently weakened the Empire and it ushered in trends that many see as marking the beginning of the end of the world of Antiquity and marking the transition to the Medieval world.[8]

Barbarian Invasions

In the reign of Alexander Severus, there was a sudden rise in the number of raids by German and other barbarians. These raids were a part of life for Rome’s frontier population but by the 230s, they became more intense and frequent.[9] German tribes became better organized and formed into confederations such as the Franks.

The emergence of the Goths, who created a large state in modern Ukraine, created a significant challenge for the Balkan and Black Sea provinces. They were militarily powerful and were especially proficient in cavalry and even took to the sea to launch piratical attacks in the 250 AD. The barbarian attacks were ferocious for two reasons. First, the Romans had been weakened by constant warfare. The bloody civil wars had been especially devasting. The Roman legions could no longer defeat foreign raids and invasions.[10]

Second, the barbarians were often desperate. Climate change and rising sea levels had impacted on their food supply and they were forced to raid deeper and deeper into Imperial Roman territories. They needed to secure resources and seize arable lands to stay alive. The continuous barbarian invasion thus weakened the Empire, and this encouraged further raiding by tribal confederations beyond the Rhine and Danube.

The Rise of Sassanian Persia

The ruins of Palmyra in present-day Syria 2010

In 224 AD, Ardashir, the ruler of Fars in modern Iran, defeated and killed the last of the Parthian kings and this is seen as the beginning of the Sassanian Empire. Its Emperors or ‘King of Kings’ portrayed themselves as the heirs of the Great Persian Empire of Xerxes.[11] It was a much more formidable state that the Parthian and within two decades, the Sassanians ruled an area much larger than anything governed by their predecessors. The neo-Persian Empire was a centralized state and had a regular army.

As soon as the Sassanians took power, they began raiding Roman Syria and Asia Minor under the capable and ruthless Shapur I. The emergence of a new force in the east was a grave challenge for the legions. The constant battles with the Germans in Europe and Persians in the Near East had overstretched the Roman Army. In consequence, the legions could not defend the frontiers. This, in turn, led to the rise of local warlords and ultimately the rise of the Palmyrene Empire, which for a time ruled almost all of the near East and even Egypt. The foundation of the Sassanian Empire, under a series of able rulers, was one of the most significant factors in the Third Century Crisis.

Natural Calamities

The inability of the Romans to defend their borders was related to socio-economic factors. A pandemic had decimated the Imperial territories in the 250s and 260s and this led to population decline. The plague according to Gibbon, ‘five thousand persons died daily in Rome, and many towns, that had escaped the hands of the barbarians, were entirely depopulated.’[12] This had serious repercussions as the army found it harder to recruit legionnaires and the tax base was much reduced, which led to serious economic dislocation. Then as we have seen climate change reduced the yield of agricultural surplus and this led to the near collapse of long-distance trade. Then the constant tax demands of the Emperors added to the dire situation in many provinces. All of these compounded the difficulties facing Rome and weakened its ability to defend itself against the Persians and Germans. However, the economic and social decline of the Empire should not be overstated, as seen in its revival under the Illyrian Emperors.

The Military Anarchy

The Third Century Crisis is sometimes known as the ‘Military Anarchy.’[13] In other words, the army was not controlled by any unified authority. The different legions sought to have their general become Emperor, because of the prestige and the monetary rewards that they would secure upon his accession. As a result, the legions in the Balkans would fight those from the Western provinces in order to determine who should become the ruler of the Roman World.

The root cause of the civil wars and endless usurpations was the fact that Rome had not developed a formal succession process even though it was a de-facto monarchy. As a result, any general with an army could intimidate the Senate to recognize his right to become the legitimate Emperor. This led to a profoundly unstable system and for almost fifty years there was rarely a strong government. Because as Gibbon noted ‘the soldiery had become aware of their power’, they disregarded any authority that was not aligned with their interests.[14] The result was endless civil wars that depleted the ranks of the legions and meant that they could not defend the Imperial provinces. It was only when the army was brought under the control of Diocletian and his reformed administration that the civil wars ended, and the legions could once again protect the Empire.


The Third Century Crisis was a fifty-year emergency when the Romans struggled to preserve their state and their way of life. There are a series of factors that led to the crisis. The constant invasions of barbarians especially German tribal confederations meant that Rome could barely defend its borders. Then the rise of the Sassanian Empire meant that the Roman legions were overstretched and constantly under pressure. The impact of the constant fighting on the economy and society was devastating and seriously undermined the ability of successive Emperors to manage the military situation. Then a series of natural disasters, including plague and climate change, damaged the Romans ability to fight. The lack of a formal succession plan for Emperors led to the army becoming the power-broker and this led to interminable civil wars and revolts. The Military Anarchy was perhaps the single most significant factor in the Third Century Crisis and the near destruction of the Roman Empire.

Further Readings

Ando, C., 2012. Imperial Rome AD 193 to 284: The Critical Century: The Critical Century (Vol. 6). Edinburgh University Press.

Liebeschuetz, Wolf. "Was there a crisis of the third century?." In Crises and the Roman Empire, pp. 11-20. (Leiden, Brill, 2007).

De Blois, Lukas. "The military factor in the onset of crises in the Roman empire in the third century AD." In The Impact of the Roman Army (200 BC-AD 476): Economic, Social, Political, Religious and Cultural Aspects, pp. 495-508 (Leiden, Brill, 2007).

Grant, M., 2013. Collapse and Recovery of the Roman Empire. London: Routledge.

Ziolkowski, Adam. "The Background to the Third‐Century Crisis of the Roman Empire." The Roman Empire in Context: Historical and Comparative Perspectives (2011): 111-133.


  1. Hekster, Oliver. Rome and its Empire, AD 193–284 (Edinburgh 2008), p 119
  2. Heckster, p 127
  3. Gibbon, Edward, Decline and Fall of the Roman Empire, chapter 6
  4. Gibbon, I, Chp 6
  5. Hekster, p 198
  6. Watson, Alaric Aurelian and the Third Century (Taylor & Francis, 2004), p 134
  7. Pat Southern. Empress Zenobia: Palmyra's Rebel Queen (London, Continuum, 2008), p. 133
  8. Brown, P, The World of Late Antiquity (W Norton, London, 1971), p. 22
  9. Southern, Pat. The Roman Empire from Severus to Constantine (London, Routledge, 2015), p 356
  10. Heckster, p 113
  11. Heckster, p 139
  12. Gibbon, I, chapter 8
  13. Scarre, Chris, Chronicle of the Roman Emperors: the reign-by-reign record of the rulers of Imperial Rome, (London, Thames & Hudson, 1995), p 198
  14. Gibbon, I, Chp. 7