It is perhaps surprising to learn that the Roman Empire is only around the 28th largest in history. It punches above its weight in terms of influence. Its sheer physical size shouldn’t be underestimated, however. It grew to around 1.93 million square miles, containing about 21 per cent of the world’s population (by an estimate) at its greatest extent in the early second century.
Rome: the village that became an empire
In the 6th century BC Rome was subservient to the Etruscans, part of a Latin League of city states that operated as loose federation, cooperating on some matters, independent on others.
By the end of the next century, Rome was flexing its muscles, fighting its first wars against its Etruscan neighbours and cementing their dominance over their former allies in the Latin War of 340 – 338 BC.
From central Italy the Romans expanded north and south, defeating the Samnites (290 BC) and Greek settlers (the Pyrrhic War 280 – 275 BC) in the South to take control of the Italian peninsular.
Roman victory in Africa and the east
In southern Italy, they butted up against another great power, Carthage, a city in modern Tunisia. The two powers first fought in Sicily, and by 146 BC Rome had utterly defeated their great maritime rival and added large parts of North Africa and all of modern Spain to their territory.
With Carthage swept aside, there was no credible rival for Mediterranean power and Rome expanded to the east, greedily acquiring land in Greece, Egypt, Syria and Macedonia. By the time of the defeat of the Achaean League in 146 BC, Roman territory was so large the growing empire (then still a republic) initiated a system of provinces with military governors.
The conquests of Caesar and beyond
Julius Caesar took Roman power to the north, conquering Gaul (roughly modern France, Belgium and parts of Switzerland) by 52 BC in the wars that gave him the popular reputation to seize power for himself. He also explored further expansion into modern Germany and over the English Channel to Britain.
Caesar is a fine example of a Roman general expanding the Empire’s territories for his own personal (and largely financial) gain.
The first Emperor Augustus pushed on into Germania, drawing back to a border along the Rhine and Danube after a disastrous defeat at the Battle of the Teutoburg Forest in 9 AD.
Britain was finally invaded in 43 AD and pacified over the following decades until the building of Hadrian’s Wall around 122 AD marked the furthest northern extent of the Roman Empire.
The Roman Empire at its height
Emperor Trajan (ruled 98 – 117 AD) was Rome’s most expansionist ruler, his death marking the high water mark of Rome’s size.
He campaigned against Dacia (modern Romania and Moldova, and parts of Bulgaria, Serbia, Hungary, and Ukraine), adding most of it to the Empire by 106 AD.
He also made conquests in Arabia and took on the Parthian Empire to add Armenia, Mesopotamia and Babylon to the Empire, while pushing on towards modern Iran, the Parthians’ power base. Roman writers were starting to dream of conquering India.
Trajan fell ill and died in 117 AD, doing what had come so naturally to him, fighting. The Roman Empire would both add and lose territories over the centuries to its final collapse around 476 AD, but would never match the extent of Trajan’s conquests, when it was possible to travel from the north of England to the Persian Gulf without leaving Roman territory.
What made Rome expand?
Why Rome was so successful at conquest and what drove it to expand from so early in its history and for so long is an interesting question with complex and inconclusive answers. Those answers might include everything from early population growth to the birth of a very military society; a belief in Roman superiority to economics and urbanisation.