Decline of Roman Empire: Causes, Timeline and What Historians Argue

Contents13

• Main explanations for the decline of the Roman Empire
• First decline: the Crisis of the Third Century, 235-284
• Recovery under Diocletian and Constantine
• The 5th-century collapse in the West
• The army of the late empire
• Money and taxation
• Generals behind the throne
• Disease and climate
• Theories most historians reject
• How historians' views have changed
• Why the East survived when the West fell
• Did the Eastern empire decline too
• Verdict: the decline of the Roman Empire

The decline of the Roman Empire is one of history's most studied questions. The empire did not collapse overnight. It nearly fell apart in the 200s. Then it recovered under strong emperors.

In the 400s it lost its Western half. Its Eastern half lived on for another thousand years. This page lays out the timeline and the main reasons historians give. It also covers the theories that most of them now reject.

TL;DR: Rome's decline came in stages. The Crisis of the Third Century (235-284) brought civil war and invasions. Coins were debased too. Diocletian and Constantine restored order. In the 400s the West lost land and tax income to Germanic peoples. The worst loss was North Africa in 439. Its last emperor was removed in 476. Historians blame a mix of causes, not one: invasion and unrest, plus money and disease.

Main explanations for the decline of the Roman Empire

In 1984 the German historian Alexander Demandt collected no fewer than 210 reasons writers had given for Rome's fall. The number shows how open the question remains.

First decline: the Crisis of the Third Century, 235-284

The first great crisis began with the murder of Emperor Severus Alexander in 235. For fifty years, emperors rose and fell in quick order. Most were raised by their own troops. Most were killed by them too. More than twenty men were hailed as emperor in this period.

The empire faced enemies on two fronts. The Sasanian Persians attacked in the east. They captured Emperor Valerian in 260.

Germanic groups raided across the Rhine and Danube. For a time the empire split into three parts. A breakaway Gallic Empire held the west (260-274). A Palmyrene state held the east under Queen Zenobia.

At the same time the silver coins were debased until almost no silver was left. Prices rose. A pandemic, the Plague of Cyprian, spread across the empire from about 250. Emperor Aurelian (270-275) joined the empire back together. He also began new walls around Rome itself.

Recovery under Diocletian and Constantine

Diocletian, emperor from 284, rebuilt the state. He shared power in the Tetrarchy and doubled the number of provinces. He split civil from military command and reorganised taxes. In 301 he issued an edict setting maximum prices. It proved unworkable.

Constantine I (306-337) carried on the rebuilding. He brought in a stable gold coin, the solidus. It stayed the standard of the Mediterranean world for centuries.

He founded Constantinople in 330 as a new capital in the east. He gave official favour to Christianity. By the mid-300s the empire was stable and strong again.

The 5th-century collapse in the West

The final crisis began outside the empire. In the 370s the Huns moved west across the steppe. They pushed Gothic groups toward the Roman frontier.

The loss of North Africa mattered more than any single battle. It supplied grain to Rome and a large share of the West's taxes. Without it, the Western government could not pay enough soldiers to win back what it had lost. For the final years, see when did the Western Roman Empire fall.

The army of the late empire

The late Roman army was large but stretched. After Diocletian and Constantine it was split in two. Frontier troops guarded the borders.

Field armies could move to meet invasions. Finding enough Roman citizens to serve grew harder. The army relied more and more on soldiers from outside the empire.

From 382, whole peoples such as the Goths were settled inside the empire as federates. They were allies who fought under their own leaders, in return for land or pay. This brought in fighting men quickly. But it also meant large armed groups inside the empire answered first to their own kings. They were hard to control when payments stopped.

Money and taxation

Paying the army was the empire's biggest cost. When income fell, the government raised taxes. Tax collection grew harsher. Laws of the 300s tied many farm tenants, called coloni, to the land they worked, so taxes could be collected. Cities lost wealth, as local elites dodged costly public duties.

Historians such as A. H. M. Jones argued that this growing burden weakened the empire from within. That began long before the final invasions.

Generals behind the throne

In the 400s, real power in the West often lay with army commanders, not emperors.

• Stilicho, of Vandal descent, defended the West for Honorius until he was executed in 408.
• Aetius led the campaign that halted Attila in 451, and was murdered by Valentinian III in 454.
• Ricimer, a general of Germanic origin, made and then unmade emperors from 456 until his death in 472.

These figures show how far the Western court depended on armies it could no longer fully control or pay.

Disease and climate

Recent research has added the environment to the story. Kyle Harper's book The Fate of Rome (2017) came out from Princeton University Press. It argues that pandemics and climate change played a major role.

• The Antonine Plague, from 165 CE, struck during the reign of Marcus Aurelius and may have killed a large share of the population.
• The Plague of Cyprian, from about 250 CE, spread during the Crisis of the Third Century.
• The Plague of Justinian, from 541 CE, the first known outbreak of bubonic plague, hit the Eastern empire after the West had already fallen.

Harper also points to a period of cooling from the 530s on. His argument has been influential, but it has also been criticised. Historians still debate how much weight to give these factors.

Theories most historians reject

Christianity, decadence and lead

Popular explanations for the fall of Rome.

Status: Disputed Widely repeated. Most modern historians reject or doubt them.

Note: Edward Gibbon, writing from 1776, partly blamed Christianity for weakening Roman civic spirit. Popular accounts often add moral decay, or lead poisoning from pipes and wine vessels. Most modern historians reject Christianity as a major cause.

They point out that the equally Christian Eastern empire survived. Ice-core studies show high lead pollution in the Roman period. But historians rarely treat lead as a major cause of the fall.

Sources: Britannica, "Ancient Rome: The Later Roman Empire"; History.com, "8 Reasons Why Rome Fell".

How historians' views have changed

Why the East survived when the West fell

Historians point to several advantages the Eastern half had in the 400s. Its cities were richer and its population larger. Constantinople was very hard to capture.

The sea and the Theodosian land walls, built in the early 400s, protected it. The East's main rival, Sasanian Persia, was a stable state that could be dealt with by treaty. And more than once, Eastern emperors paid invaders or urged them to move west, toward Italy and Gaul.

Did the Eastern empire decline too

The East took a different path. It survived the 400s. It won back lands in the West under Justinian in the 500s. It stayed a major power until the 1000s.

Its long decline came later. It lost to the Seljuk Turks at Manzikert in 1071. The Fourth Crusade sacked Constantinople in 1204. The Ottomans took it in 1453. That story is told on the Eastern Roman Empire hub.

To read more, see our guide to the best Roman history books. It covers Rome from the Republic to 1453.

Verdict: the decline of the Roman Empire

The decline of the Roman Empire was slow and uneven, with many causes at once. The West survived one near-collapse in the 200s. Then in the 400s it lost land and income, and with them control of its armies. It ended in 476-480.

Historians still argue over the balance of causes. Some prefer to speak of change rather than decline. What is not in dispute is that the Eastern half lasted until 1453. For the empire at its height, see the Roman Empire page.

Sources checked for this page

• Britannica, "Ancient Rome: The Later Roman Empire"
• Britannica, "Reflections on the Causes of the Grandeur and Decline of the Romans"
• World History Encyclopedia, "The Crisis of the Third Century"
• World History Encyclopedia, "Antonine Plague"
• Princeton University Press, Kyle Harper, "The Fate of Rome"
• History.com, "8 Reasons Why Rome Fell"
• EBSCO Research Starters, "Fall of Rome"

Questions people also ask

What were the main causes of the decline of the Roman Empire?

Historians usually point to several causes working together: pressure from invading peoples, civil wars and unstable leadership, heavy military costs and taxation, the loss of rich provinces such as North Africa, and epidemics. No single cause is accepted by all historians.

When did the decline of the Roman Empire begin?

Many historians see the Crisis of the Third Century, from 235 to 284, as the first great period of decline, although the empire recovered afterwards. The final collapse in the West came in the 5th century.

Did Christianity cause the fall of Rome?

Edward Gibbon argued that it weakened Roman civic spirit, but most modern historians reject this as a major cause. The Eastern empire was equally Christian and survived for another thousand years.

Did lead poisoning cause the fall of Rome?

The idea was popular in the 20th century, and ice cores show high lead pollution in the Roman era. But most historians do not treat lead as a significant cause of the empire's decline.

Who wrote The Decline and Fall of the Roman Empire?

The English historian Edward Gibbon. Its six volumes were published between 1776 and 1789, and it remains the most famous account of the subject, though many of its judgements have been revised.

How long did the decline of the Roman Empire take?

It depends on the starting point. From the Crisis of the Third Century in 235 to the deposition of the last Western emperor in 476 is about 240 years, and the Eastern empire continued until 1453.