The Roman Empire: rise, peak and fall

An empire that begins without a battle

The Roman Empire does not start with a conquest. It starts with a change of regime from within: in 27 BC Octavian, Julius Caesar’s great-nephew and adopted son, becomes Rome’s first emperor and takes the name Augustus. The state already existed, so did the provinces; what changes is who decides.

The Senate grants him authority over the provinces and tribunician power, which lets him pass laws through the popular assemblies: on paper two distinct powers, in practice control of the state. The institutions of the Republic formally stay in place (magistrates are still elected, the Senate still meets), but the final say belongs to one person. It is a gradual, almost quiet transition, and that is precisely why it works: there is no morning on which Romans wake up inside a system they do not recognise.

Augustus rules until AD 14. Ancient writers passed down the line that he found Rome a city of brick and left it a city of marble. The less quoted but more consequential fact is a different one: under him the road network is extended and kept in working order, and the seas are cleared of pirates. From then on, goods move.

That network was neither his work nor the work of a single century: the Via Appia dates from 312 BC, and Roman public roadway would eventually pass 120,000 kilometres over five centuries of building.

The Pax Romana: two centuries when trade paid off

The period Augustus opens is called the Pax Romana, and it lasts over two hundred years, until the death of Marcus Aurelius in AD 180. The name is slightly misleading: it does not mean fighting stopped. Campaigns on the frontiers went on without pause, and twenty-three professional legions were stationed there for exactly that reason. It means that inside the borders security held long enough to make it sensible to open a business a thousand kilometres from home.

Between AD 96 and 180 five rulers succeed one another, the ones historians call the Five Good Emperors: Nerva, Trajan, Hadrian, Antoninus Pius and Marcus Aurelius. It is the stretch of Roman history when the empire is at its largest and most stable.

Emperor	Reign	What he is remembered for
Nerva	96-98	Opens the run of successions by adoption
Trajan	98-117	Conquers Dacia; the empire’s greatest extent
Hadrian	117-138	Consolidates the frontiers; from 122 builds the Wall in Britain
Antoninus Pius	138-161	The longest and quietest reign of the five
Marcus Aurelius	161-180	Wars on the Danube; his death ends the Pax Romana

Trajan and the furthest point

Trajan reigns from AD 98 to 117. Born at Italica, near modern Seville, on 18 September AD 53, he is the first emperor who does not come from Italy — which already says something about how the empire worked.

Between 101 and 106 two campaigns break the Dacia of King Decebalus, which is absorbed and resettled with Roman colonists: roughly, modern Romania. Between 114 and 116 he annexes Armenia and Mesopotamia, going as far as taking Ctesiphon, the Parthian capital. At his death, on 9 August 117, the borders run from northern Britain to the Caspian Sea: no successor will push them further.

The Dacian spoils pay for Trajan’s Forum, dedicated in 112, and for Trajan’s Column the year after: thirty metres of marble up which a spiral frieze tells the Dacian campaigns without a break, with the emperor’s ashes buried at its base. It is one of the few ancient works where official propaganda and historical record are the same object.

What held fifty countries together

Around AD 100, on the most generous estimates, up to a hundred million people lived inside the empire, on territory that today belongs to some fifty different states. In the second century the limes, the frontier line, ran for more than five thousand kilometres: one continuous arc starting in northern Britain, crossing Europe and carrying on to the Near East and the deserts of North Africa.

Governing something like that, with no telephones and no engines, took more than military force, as the most visible case of all shows.

Practical example: in AD 122, after the emperor Hadrian’s visit to Britain, the army starts building a barrier 73 miles long — 80 Roman miles — from Wallsend on the River Tyne to Bowness-on-Solway. It took at least six years. The plan called for a milecastle guarding a gate every Roman mile, with two observation turrets between each pair; while work was under way 14 forts were added, a little over seven miles apart, along with an earthwork to the south known as the Vallum. It stayed the empire’s north-west frontier for nearly three hundred years.

Then there was the law. In AD 212 the emperor Caracalla issues the Constitutio Antoniniana, granting Roman citizenship to all free inhabitants of the empire and erasing the distinction between Italians and provincials. The stated motive was equality; the practical one, as the Metropolitan Museum notes, was fiscal: money was needed after the huge sums lavished on the army, and widening the pool of citizens widened the base of the inheritance tax. The long-term effect was profound anyway, because citizenship stopped being a privilege to be earned and became the ordinary status of anyone living in the empire, speeding up a shift towards the provinces that was already under way: Trajan, a Spaniard, had been emperor a century earlier.

And there were the cities, built everywhere to the same recognisable template. The Colosseum, officially the Flavian Amphitheatre after the dynasty that built it in the first century AD, is the monumental version of a model repeated in hundreds of smaller towns. It opened in AD 80 under Titus with a hundred days of games, and held roughly 45,000 seated spectators plus another 5,000 standing. The nickname is not explained by its size: scholars trace it to a colossal statue that once stood beside it. It remains, all the same, the largest amphitheatre in the world.

The third-century crisis and the reforms

Between AD 235 and 284 the empire goes through what historians call the crisis of the third century: half a century of political instability, with emperors following one another in quick succession, pressure on the borders and economic trouble.

The answer comes with Diocletian. In 285 he appoints a colleague for the West and splits the administration in two; from 293 he extends it to four rulers, the tetrarchy. Not to break the empire apart, but because a territory that size had become ungovernable from a single centre. Constantine, proclaimed emperor by his troops in 306 and master of the West after his victory at the Milvian Bridge in 312, becomes sole ruler of the whole empire in 324; in 330 he founds Constantinople, on the Bosphorus, which becomes the new political capital. In 395 the separation between East and West becomes formal and final.

The same caveat applies as with the Cold War: a line drawn on a map for practical reasons can harden, over time, into two worlds that no longer speak to each other. With one substantial difference: in the Roman case the split was not an ideological rupture but an administrative choice that time made irreversible.

476, and what it actually means

In 410 Alaric’s troops sack Rome; in 455 it is the Vandals’ turn. These are severe blows to prestige, but they are not the end. The conventional date is another: 4 September 476, when the Germanic king Odoacer deposes the emperor Romulus Augustulus. The name is almost a joke of history: the last western emperor was called after both the city’s legendary founder and the first emperor, each in diminutive form.

Why did it fall? Not for a single reason, and historians are wary of single-cause explanations. The instability accumulated in the third century counts, as do the rising cost of an enormous army and administration, the difficulty of defending thousands of kilometres of frontier, and the pressure of peoples pushing at the borders. The limits of the date itself count too: as historians observe, the cataclysmic character of 476 has ended up masking how much continuity lay underneath. Cities went on existing, Roman law stayed in use, the language turned into the Romance languages rather than disappearing. In Britain, for instance, the latest coins found along Hadrian’s Wall date to AD 403-406: the Romans had already left seventy years before 476, without anyone declaring it.

The other half, the one that did not fall

Here lies the most widespread misunderstanding. What ends in 476 is the Western Empire. The East carries on, with its capital at Constantinople, for nearly another thousand years: until 29 May 1453, when the Ottoman sultan Mehmed II takes the city. The last emperor, Constantine XI Palaiologos, dies in the fighting on the walls; his body was never identified with certainty, and the traditional account, the emperor throwing away his regalia and charging into the melee, comes from chronicles written in the years that followed.

We call it the Byzantine Empire, but that is a label scholars coined after it was gone. The people living in it called their state the Roman Empire and themselves Romans. This was not a rhetorical claim: it was the continuation of the same state structure born in 27 BC.

Why we still study it

Few civilisations have left traces this concrete two thousand years on. The borders of many European states still partly follow Roman administrative divisions. Half the civil law of the continent descends from Roman law. And the languages of Italy, France, Spain, Portugal and Romania are nothing but Latin, changed by time.

For a sense of the timescale: more than three thousand years separate the unification of Egypt under Menes from the Roman conquest, and ancient Egypt remains the natural comparison for sheer longevity. The Roman Empire is shorter but wider, and above all it left an administrative organisation that outlived it. When post-revolutionary France had to build itself a new political vocabulary, it went there for it: the Republic of 1792, then the Senate, the Consulate and the Tribunate of the 1799 constitution, are all Roman words put back into service. The French Revolution closed one era using the language of another. And the Industrial Revolution was, among other things, the first moment when Europe built a transport network comparable in ambition to the Roman roads, about eighteen centuries late.