Environment and Empire

The Shape of the Roman Empire

Rome's rise is a story with the capacity to astonish us, all the more so since the Romans were relative latecomers to the power politics of the Mediterranean. By established convention, Rome's ancient history is divided into three epochs: the monarchy, the republic, and the empire. The centuries of monarchy are lost in the fog of time, remembered only in fabulous origins myths that told later Romans how they came to be. Archaeologists have found the debris of at least transient human presence around Rome going back to the Bronze Age, in the second millennium BC. The Romans themselves dated their city's founding and the reign of their first king, Romulus, to the middle of the eighth century BC. Indeed, not far from where Claudian stood in the forum, beneath all the brick and marble, there had once been nothing more than a humble agglomeration of wooden huts. This hamlet could not have seemed especially propitious at the time.

For centuries, Rome stood in the shadow of her Etruscan neighbors. The Etruscans in turn were outclassed by the political experiments underway to the east and south. The early classical Mediterranean belonged to the Greeks and Phoenicians. While Rome was still a village of letterless cattle rustlers, the Greeks were writing epic and lyric poetry, experimenting with democracy, and inventing drama, philosophy, and history as we know them. On nearer shores, the Punic peoples of Carthage built an ambitious empire, before the Romans knew how to rig a sail. Fifteen miles inland, along the soggy banks of the Tiber River, Rome was a backwater, a spectator to the creativity of the early classical world.

Around 509 BC the Romans shuffled off their kings and inaugurated the republic. Now they gradually step into history. From the time they are known to us, Rome's political and religious institutions were a blend of the indigenous and the adopted. The Romans were unabashed borrowers. Even the first code of Roman law, the Twelve Tables, was proudly confessed to be plagiarized from Athens. The Roman republic belongs among the many citizenship-based political experiments of the classical Mediterranean. But the Romans put their own accents on the idea of a quasi-egalitarian polity. Exceptional religious piety. Radical ideologies of civic sacrifice. Fanatical militarism. Legal and cultural mechanisms to incorporate former enemies as allies and citizens. And though the Romans themselves came to believe that they were promised imperium sine fine by the gods, there was nothing ineluctable about Rome's destiny, no glaring geographical or technological secret of superiority. Only once in history did the city become the seat of a great empire.

Rome's rise coincided with a period of geopolitical disorder in the wider Mediterranean in the last centuries before Christ. Republican institutions and militaristic values allowed the Romans to concentrate unprecedented state violence, at an opportune moment of history. The legions destroyed their rivals one by one. The building of the empire was bloody business. The war machine whetted its own appetite. Soldiers were settled in rectilinear Roman colonies, imposed by brute force all over the Mediterranean. In the last century of this age of unbridled conquest, grand Shakespearean characters bestride the stage of history. Not by accident is western historical consciousness so disproportionately concentrated in these last few generations of the republic. The making of Rome's empire was not quite like anything that had happened before. Suddenly, levels of wealth and development lunged toward modernity, surpassing anything previously witnessed in the experience of our species. The teetering republican constitution generated profound reflections on the meaning of freedom, virtue, community. The acquisition of imperial power inspired enduring conversations about its proper exercise. Roman law helped to birth norms of governance, by which even the masters of empire might be held to account. But the scaling up of sheer power also fueled the cataclysmic civil violence that ushered in an age of autocracy. In the apt words of Mary Beard, "the empire created the emperors — not the other way round."

By the time Augustus (r. 27 BC–AD 14) brought the last meaningful stretches of the shore under Roman dominion, it was no idle boast to call the Mediterranean "mare nostrum," our sea. To take full measure of the Roman accomplishment, and to understand the mechanics of ancient imperialism, we must know some basic facts about life in an ancient society. Life was slow, organic, fragile, and constrained. Time marched to the dull rhythms of foot and hoof. Waterways were the real circulatory system of the empire, but in the cold and stormy season the seas closed, and every town became an island. Energy was forbiddingly scarce. Human and animal muscle for force, timber and scrub for fuel. Life was lived close to the land. Eight in ten people lived outside of cities. Even the towns had a more rural character than we might imagine, made lively by the bleats and brays — and pungent smells — of their four-legged inhabitants. Survival depended on the delivery of rain in a precarious environment. For the vast majority, cereals dominated the diet. "Give us this day our daily bread" was a sincere petition. Death always loomed. Life expectancy at birth was in the 20s, probably the mid-20s, in a world where infectious disease raged promiscuously. All of these invisible constraints were as real as gravity, defining the laws of motion in the world the Romans knew.

These limits cast into relief the sheer spatial achievement of the Roman Empire. Without telecommunications or motorized transport, the Romans built an empire connecting vastly different parts of the globe. The empire's northern fingers reached across the 56 parallel, while the southern edges dipped below 24° N. "Of all the contiguous empires in premodern history, only those of the Mongols, Incas, and Russian czars matched or exceeded the north-south range of Roman rule." Few empires, and none so long-lived, grasped parts of the earth reaching from the upper mid-latitudes to the outskirts of the tropics.

The northern and western parts of the empire were under the control of the Atlantic climate. At the ecological center of the empire was the Mediterranean. The delicate, moody features of the Mediterranean climate — arid summers and wet winters against a relatively temperate backdrop — make it a distinct type of climate. The dynamics of a giant, inland sea, combined with the knuckled texture of its inland terrains, pack extreme diversity into miniature scale. Along the empire's southern and eastern edges, the high pressure of the subtropical atmosphere won out, turning the land into pre-desert and then...