Pax Romana (27 BC-AD 180): Two Centuries of Roman Peace

The Pax Romana, Latin for “Roman peace”, was a period of about two centuries, conventionally dated from 27 BC to AD 180, during which the Roman Empire enjoyed unusual internal stability and prosperity. It began when Augustus ended Rome’s civil wars and lasted until the death of the emperor Marcus Aurelius. The term describes peace within the Mediterranean world rather than an absence of war, but it shaped the image of Rome as a civilisation of roads, cities and law.

Defining the Pax Romana

There is no single official start or end date. Most historians begin with the settlement of January 27 BC, when Octavian became Augustus, or with his victory at Actium in 31 BC, which ended the civil wars. The usual end point is the death of Marcus Aurelius on 17 March AD 180 and the accession of his son Commodus.

Romans themselves spoke of peace as something imposed through victory. Augustus closed the doors of the Temple of Janus in Rome, a sign that the Roman world was at peace, three times during his reign. The Senate also voted the Altar of Augustan Peace, the Ara Pacis, dedicated in 9 BC. The expression pax Augusta, “Augustan peace”, came first; pax Romana appears in writers such as Seneca and Pliny the Elder in the first century AD.

In the eighteenth century the historian Edward Gibbon described the period from the death of Domitian in AD 96 to the accession of Commodus in 180 as perhaps the happiest and most prosperous time in human history. Modern scholars treat that verdict with caution, but his framing helped fix the idea of a Roman golden age.

How the peace was maintained

The foundation was a permanent professional army stationed mostly on the frontiers. Under Augustus there were 28 legions, later 25 to 30, together with roughly equal numbers of non-citizen auxiliary troops. Estimates of total strength range from about 250,000 to 400,000 men, a large force but small for an empire of tens of millions.

Political stability came from the Principate, the system of rule by a single princeps or emperor. Provincial governors were appointed and watched more closely than under the Republic, which reduced some of the worst plundering of the provinces. Local elites in thousands of cities ran their own affairs and collected taxes, and many gradually received Roman citizenship.

From the late first century, frontiers were increasingly fixed and fortified. Roads and forts lined the Rhine and Danube, and in Britain the emperor Hadrian built a wall across the north of the province from AD 122. Hadrian’s Wall is the best-known example of a policy that shifted from expansion towards holding what Rome already controlled.

Economy, trade and cities

Peace at sea and on land allowed trade to grow across the Mediterranean, which Romans called “our sea”. Shipwreck finds from the period are far more numerous than in earlier or later centuries, which suggests a peak in seaborne trade. Grain from Egypt and North Africa fed the city of Rome, while olive oil from southern Spain was shipped in such quantities that the broken jars formed an artificial hill in Rome, Monte Testaccio.

Long-distance trade reached far beyond the frontiers. Roman ships sailed from Red Sea ports to India using the monsoon winds, and spices, pepper, silk and gems flowed west. Pliny the Elder complained that luxury imports from India, China and Arabia drained the empire of large sums of money each year. In AD 166 a group claiming to be envoys of the emperor reached Han China, as recorded in Chinese sources.

Cities flourished across the provinces. They received paved streets, forums, baths, theatres, amphitheatres and aqueducts, often paid for by local notables seeking honour. A network of main roads estimated at more than 80,000 kilometres linked them, alongside many more minor routes. The empire’s population is usually estimated at around 50-70 million people at its peak in the second century.

Culture, law and religion

Stable rule encouraged a shared culture across the empire. In the West, Latin spread through the army, colonies and local elites, and it later developed into the Romance languages such as French, Spanish and Italian. In the East, Greek remained the main language of cities, education and literature, and the empire was in practice bilingual.

Roman law developed steadily during the period. Emperors answered petitions and legal questions with written rulings, and professional jurists such as Gaius, whose Institutes were written in the mid-second century, organised legal principles in ways that later influenced European legal systems. Roman citizenship spread gradually to provincial elites and veterans, long before it was extended to almost all free inhabitants in AD 212.

Religion was generally tolerant of local gods, as long as communities also honoured the emperor and the gods of Rome. The imperial cult, the worship of deified emperors and of the emperor’s spirit, spread through temples and festivals in the provinces. Christianity emerged during this period and spread along the empire’s roads and sea routes. Christians were sometimes persecuted locally, as the correspondence between Pliny the Younger and Trajan around AD 112 shows, but there was not yet a systematic empire-wide persecution.

The period also produced much of the Latin and Greek literature that later generations regarded as classical, from Virgil, Horace and Livy under Augustus to Tacitus, Plutarch and Galen in the late first and second centuries.

The limits of the peace

The Pax Romana was not peaceful for everyone. Expansion continued, and the empire reached its greatest extent under Trajan around AD 117. Conquests included Britain from AD 43, Dacia in 101-106 and, briefly, Mesopotamia. Defeats also happened: in AD 9 three legions were destroyed in the Battle of the Teutoburg Forest in Germany.

Revolts against Roman rule were put down with great force. Boudica’s uprising in Britain in AD 60-61 cost tens of thousands of lives. The First Jewish-Roman War (AD 66-73) led to the destruction of Jerusalem and its Temple in AD 70, and the Bar Kokhba revolt of 132-136 was crushed with heavy loss of life in Judaea.

Rome itself was not free of political violence. Several emperors were murdered, and after Nero’s death the empire went through a civil war in AD 69, the Year of the Four Emperors. Peace also depended on a society built on slavery and on sharp inequality. In Tacitus’s Agricola, the British leader Calgacus says of the Romans: “They make a desert and call it peace.” The words are Tacitus’s own composition, but they show that Romans themselves recognised the cost of imperial peace.

The Five Good Emperors

The period from AD 96 to 180 is often seen as the high point of the Pax Romana. Nerva, Trajan, Hadrian and Antoninus Pius each adopted a capable successor rather than relying on birth, which provided a series of experienced rulers. Antoninus Pius, who reigned from 138 to 161, presided over a reign with few major wars.

Marcus Aurelius, who ruled from 161 to 180, is remembered as a philosopher-emperor and the author of the Meditations. Yet his reign was dominated by war. Conflicts with Parthia in the East were followed by long wars against the Marcomanni and other peoples on the Danube, and the Antonine Plague, which spread from around 165, killed a large number of people; estimates of the death toll range widely, from a few percent to a quarter or more of the population in some regions.

How it ended

When Marcus Aurelius died in 180, his son Commodus succeeded him, breaking the pattern of adoption. Commodus’s reign was marked by plots and executions, and his murder in 192 was followed by civil war in 193. The Severan dynasty restored order for a time, but the cost of the army and pressure on the frontiers kept growing.

From 235 the empire entered the crisis of the third century, a half-century of rapid changes of emperor, invasions, breakaway states and economic trouble. By then the Pax Romana was already a memory that later Romans looked back on with nostalgia.

By the numbers

Timeline

• 31 BC, 2 September: Octavian’s victory at Actium ends the civil wars.
• 27 BC, January: Octavian receives the name Augustus; the Principate begins.
• 9 BC, 30 January: The Ara Pacis, the Altar of Augustan Peace, is dedicated in Rome.
• AD 9: Three legions are destroyed in the Teutoburg Forest.
• AD 69: The Year of the Four Emperors brings a brief civil war.
• AD 70: Roman forces destroy Jerusalem and its Temple.
• AD 117: The empire reaches its greatest extent at Trajan’s death.
• AD 122: Construction of Hadrian’s Wall begins in Britain.
• c. AD 165: The Antonine Plague begins to spread across the empire.
• AD 180, 17 March: Death of Marcus Aurelius, the usual end of the Pax Romana.

Why it matters

The Pax Romana allowed Roman law, Latin and Greek culture, cities and later Christianity to spread across a vast area. Many of Europe’s roads, towns and legal ideas trace back to this era. It also became a powerful model, and later empires and powers spoke of a “Pax Britannica” or “Pax Americana” in imitation of it, for good and for ill.