THINKERS AT WAR – Marcus Aurelius

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Iain King looks as the philosophy of Emperor Marcus Aurelius

One of Rome’s most remarkable rulers, Marcus Aurelius (AD 121-180) is commonly regarded as the last of ‘the five good emperors’. Along with his predecessors – Nerva, Trajan, Hadrian, and Antonius Pius – Marcus brought stability to an unstable empire. The five presided over almost a century of competent government in the age of that Gibbon considered the most ‘golden’.

Marcus AureliusBut it was Marcus Aurelius, the philosopher-emperor, who inadvertently brought this golden age to an end.

He had been singled out for an imperial life when he was still a teenager. The dying Hadrian had instructed his successor, Antonius Pius, to adopt the young philosopher. Antonius Pius, one of longest-serving emperors, became infirm in his last years, so Marcus Aurelius gradually assumed the imperial duties. By the time he succeeded in AD 161, he was already well-practised in public administration.

The Eastern Question

Marcus immediately became the first emperor to appoint a co-ruler. It was a clever arrangement: it made it much harder for usurpers to snatch power, since they had to assassinate two rulers, not one. It also recognised that the empire had become too huge to administer from a single capital.

Marcus’ cousin Lucius Verus was given responsibility for the eastern half of the Empire and made responsible for confronting the Parthians (who controlled Persia), which had just moved into the buffer state of Armenia. Recognising flaws in Lucius’ character, however, Marcus made sure that his co-emperor was accompanied by trustworthy generals. Even so, Lucius’ victorious five-year campaign was marred when his army plundered a city even after it had surrendered.

Although he was far from the action, Lucius’ campaign in the East shaped Marcus’ reign in three ways. First, it meant that the senior emperor was free to concentrate on administration and public affairs. Contemporary accounts describe him as very judicious and deeply interested in the processes of government.

Even allowing for court propaganda, it is reasonable to assume that Marcus had an affinity for the decision-making role demanded by high office. He would certainly need it – because of two further implications of the Parthian campaign.

Plague and barbarians

Lucius’ soldiers did not come home from the wars just with trophies; they also brought back a plague. Possibly a strain of smallpox, it is estimated to have killed some five million Roman citizens – perhaps 10% of the total – including the co-emperor Lucius himself in AD 169. As well as destabilising Roman society, the plague made the Empire vulnerable to invasion.

To garner forces for the Eastern campaign, Marcus Aurelius had slimmed down his troops on the long European frontier – roughly demarcated by the Rhine and the Danube rivers. Aware he was weakening his defences, he had warned his local governors against provoking the borderland tribes. It did not work. Germanic tribes raided west into Gaul, and, in AD 166, the Marcomanni of Bohemia broke their alliance with Rome and launched a much more serious invasion across the Danube.

Marcus Aurelius was forced to act. Unlike previous emperors, who had spent many years campaigning in the provinces, Marcus was a relative novice at expeditionary warfare. But he duly left for the front, stationing himself in modern-day Serbia and Austria, in an effort to repulse the invasion.

He suffered two early defeats, and the barbarians crossed the Alps and mounted the first successful invasion of Italy in two and a half centuries, attacking the Roman city of Aquileia.


It was during these campaigning years that Marcus wrote his famous Meditations. Removed from the cultural and intellectual life of Rome, he may have turned to philosophy for mental stimulation. But the books also reveal a moral exploration – as if the Emperor were searching for guidance as he made testing and important decisions without any source of reflection other than himself.

He concludes on advice which is at odds with the brutality of his situation. Whereas many in the Roman world had no qualms about being cruel, and some even revelled in it, Marcus Aurelius reveals himself to be a considerate, even sensitive man.

He remained on the front until the climax of his wars against the Germanic tribes. He won perhaps his most important battle at the end of AD 173, fought over a frozen part of the River Danube. The Quadi and Iazyges tribes had formed an alliance. The Emperor was outnumbered and surrounded. But Marcus ordered his men to form square, covered by a shield-wall, with the cavalry (including himself) protected in the centre.

Even though the tribesmen had trained their horses to ride over ice, they were unable to break the Roman formations, and, in close-quarter fighting, superior Roman discipline won out. The Quadi and Iazyges were routed. In AD 175 the Roman Emperor was able to impose punitive peace terms on both tribes.

Marcus had almost ended the Germanic threat, but he died in AD 180 before what was to be the final confrontation. Commodus, his son, successor, and by all accounts a megalomaniac, wasted the advantage so that he could return to the pleasures of Rome.

The Column of Marcus Aurelius.
The Column of Marcus Aurelius.

For all his wisdom, Marcus Aurelius had entrusted a vain teenager with imperial office (Commodus is depicted with some accuracy in the film Gladiator). The move established the principle of genetic rather than meritocratic inheritance at Rome.

Marcus Aurelius was undoubtedly a great man: an intellectual who navigated Rome masterfully through severe difficulties. The tragedy is that his philosophy – which is about self-restraint, duty, and respect for others – was so abjectly abandoned by the imperial line he anointed on his death.

The Fall of the Roman Empire

The most famous account of the end of Rome, Edward Gibbon’s The History of the Decline and Fall of the Roman Empire, starts by describing Marcus Aurelius as the last of the good emperors. Ominously, the book says that all the factors which eventually caused Rome to collapse became evident during his reign.

Military factors certainly drained Rome’s strength. For several centuries, the Empire fought intermittently with the Persians and their successors in the Middle East. They also battled along their frontiers with various Germanic tribes, and later confronted barbarians on Roman soil.

Vital negotiations were mishandled, provoking the Empire’s enemies to storm the city of Rome in AD 410 and to ravage it again in AD 455. By then, the old superiority of the Roman military machine was fast waning, and the balance of power on the battlefield was shifting to the Germanic barbarians of Central Europe.

The Western Roman Empire’s last major military expedition was to Libya in AD 468 – an attempt to seize from the Vandals the grain supply on which Italy depended. The mission ended in disaster, and the former superpower was starved into disintegration.

But Rome fell victim to these military challenges because of other weaknesses. Marcus Aurelius had to deal with only one serious usurper, but future Emperors faced many, and often succumbed to them: civil wars directed Rome’s military manpower against itself.

Rome was also afflicted by social tensions and a shift in attitudes which made citizens less willing to fight for the Empire. Gibbon called it ‘a decline in civic virtue’.

It is hard to know which of several inter-related reasons caused Rome’s collapse, and the whole process has been endlessly debated ever since. Lead poisoning, plagues, climate change, demographics, aristocratic in-breeding, Christianity, and economic causes have all been cited.

Many commentators have sought explanations from their own times. Edward Gibbon was an English MP who wrote his masterpiece between 1776 and 1789, just as the British Empire was losing their American colonies. His end-of-empire then seemed very contemporary.

This article was featured in issue 48 of Military History Monthly.

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