Pax Romana
Rome's two centuries of internal peace and prosperity, 27 BC to AD 180, enforced by the legions and undone by its lack of orderly succession.
For roughly two centuries, from 27 BC to AD 180, you could travel from the wall in northern Britain to the banks of the Euphrates without crossing a single hostile border, spending the same coins and appealing to the same law the entire way. This was the Pax Romana, the 'Roman Peace,' the long stretch of internal stability that ran from the reign of Augustus to the death of Marcus Aurelius. It is remembered as a golden age. The word 'peace,' though, conceals as much as it advertises.
What the peace bought
The achievement was real. With the Mediterranean cleared of pirates and the frontiers held by a standing army, goods and people moved as never before. A network of paved roads and open sea lanes carried grain from Egypt, wine from Gaul, and pepper and silk that had traveled overland from India and China to the markets of Rome. A common coinage and a shared body of law let a merchant in Lyon and a merchant in Antioch do business on the same terms. Cities filled with aqueducts, baths, and theaters, and a rough cultural common ground stretched from Britain to Syria. For those safely inside the system, it was a very good time to be alive.
The peace of the sword
It was also a peace imposed at spearpoint. Augustus kept some 28 legions permanently under arms, and the calm of the interior rested on relentless force at the edges and on an economy that ran on slavery. On the frontiers and among the conquered, 'peace' often meant conquest, deportation, and massacre. When Judaea revolted, Roman armies under Titus stormed Jerusalem in AD 70 and destroyed its temple. The historian Tacitus put the sharpest verdict in the mouth of a British chieftain describing Rome's method: they make a desert and call it peace. The order was genuine, and so was the violence that produced it.
The flaw in the name
Beneath the prosperity sat a structural weakness the phrase 'Roman Peace' politely ignores: Rome never solved the problem of succession. There was no fixed, lawful rule for who became emperor when one died. Power passed by adoption, by inheritance, by murder, or by whichever general could reach the capital with the most soldiers behind him. When the emperor Nero fell in AD 68, four rivals seized the throne in a single bloody year. Every peaceful transition was, in effect, luck. Marcus Aurelius, the last of the so-called good emperors, broke the run of adoptions by handing power to his own unstable son, Commodus, and the long peace began to unravel. The stability had always depended on the character of one man, with no machinery underneath to catch the empire when a bad one arrived.
That is the lasting lesson buried in the phrase. 'Pax Romana' became the model for every later claim that a single dominant power could hold the world steady, from the Pax Britannica of the nineteenth-century Royal Navy to talk of a Pax Americana after 1945. Each borrowed Rome's promise of order guaranteed by one hegemon. Each also inherited Rome's hardest question, the one the Romans never answered: what happens to the peace when the power holding it up begins to fail.