Ruins of the ancient Greek and Roman city of Cyrene, in Shahhat, Libya. (Esam Omran Al-Fetori/Reuters)

What does a republic in decline look like?

It’s an increasingly pressing question for the United States, where rising economic inequality is creating stress, anxiety and resentment. Endemic racism and ethnic prejudice are leading to clashes over citizenship and voting rights. Rampant corruption and ruthless ambition among elites are triggering political clashes that may crack the once-indestructible foundations of the American Republic — an unthinkable idea even a few decades ago, in the triumphalist aftermath of the Cold War.

Yet the seeds of American decline were sown not in the past 15 years of war and recession but in the 1970s, when economic inequality began to rise, a process that has only accelerated in recent years. As the decline of the Roman Republic shows, sharp inequality, left unaddressed, can be catastrophic, unleashing political and social consequences that can bring even a centuries-old republic to its end.

In 146 B.C., Rome completed its conquest of both Greece and Carthage and emerged as the most dominant power in the Mediterranean. There was no power left to challenge the legions, and over the course of the next century, Rome enveloped the rest of the region on its way to becoming the greatest and most enduring empire in the ancient world.

But as a result of this imperial triumph, the republican system under which the Romans lived collapsed. Since 509 B.C., Rome had been famous for its system of cooperative and participatory government that combined executive magistrates with an aristocratic Senate and democratic assemblies. For centuries, the republic persisted, and no single man ever seized power. But within 100 years of Rome’s imperial victories in 146, the republican system would be dead. The triumph of the Roman Republic was simultaneously the beginning of the end of the Roman Republic.

The early destabilization of the republic was caused by skyrocketing economic inequality. As a result of Rome’s military conquests, the wealth of the known world was brought back to Italy in the baggage trains of the victorious legions. And as Rome became the great center of the Mediterranean, the trade networks that linked cities and kingdoms from Spain to Syria now revolved around Rome. But this flood of new wealth was not shared equally — it instead concentrated in the hands of a small clique of aristocratic senatorial families who now controlled fortunes on a scale unimaginable to their austere ancestors.

And while the rich got richer, the poor got poorer. Lower-class Roman families — small citizen-farmers who had long been the backbone of the republic — faced a dire economic crisis. Prolonged military service had left many of their farms ruined. Unable to compete with growing estates of their senatorial neighbors, small freeholders were bought out by rich families. This began a century-long process that transformed Italy from a patchwork of small farms to a handful of huge commercial estates. The poorer Romans were reduced to being landless peasants or moving to the cities in search of wage labor. Either way, they were dislocated from their traditional ways of life and not very happy about it.

The plight of the dispossessed citizen-farmer was exacerbated by the simultaneous influx of slaves into Italy. Like all ancient societies, Rome had always used slaves. But it wasn’t until after it had emerged as the strongest power in the Mediterranean that slaves by the hundreds of thousands flooded into Italy. From physical labor to skilled arts and crafts, the work of the Roman economy was increasingly performed by slaves. So just as lower-class citizens were pushed off their land, they were forced into a labor market flush with slaves with whom they could not hope to compete.

Some in the Roman leadership could see clearly by the 130s and 120s B.C. that this socioeconomic dislocation was becoming an acute problem. They could see that, out in the countryside, families were losing their land, and in the cities, grain shortages were leading to panic and starvation. These poor families were certainly not sharing the benefits of Rome’s imperial wealth and power. So a new breed of popular reformers led by the Gracchi brothers, introduced laws aimed at restoring some dignity to those left behind — land redistribution, subsidized grain and a general reduction in the power of the senatorial oligarchy.

But most in the Senate resisted these efforts. More than anything else, the senatorial families remained narrowly focused on their own elite political rivalries and were obsessed with maintaining the balance of power inside the Senate. No one, for example, could afford to let a rival get credit for a popular land redistribution bill or a popular grain subsidy. The constantly revolving rounds of senatorial infighting wound up blocking all popular reform, risking the long-term health of the republic for a short-term political advantage.

This stubborn resistance to change opened the door to a darker side of popular resentment at the elites. When reasonable attempts at reform failed, populist demagogues were able to exploit the resentment, anxiety and desperation of burdened families. They promised to take land from the rich and redistribute it to the poor, offered free grain to the urban population and promised to prosecute senators for corruption. But these demagogues were much less interested in actually following through on these promises. It was not social reform they cared about but rather the acquisition of power. They saw popular anger simply as a means to an end.

This combative and increasingly toxic atmosphere led to the collapse of all of the unspoken rules of political behavior. Without these constraints, as the years passed, the issues at stake ceased to be as important as winning feuds built on mutual escalation and cycles of vengeance. Writing decades later, in the midst of the final civil wars that destroyed the republic, the historian Sallust reflected on the beginning of the end of the republic, noting, “It is this spirit which has commonly ruined great nations, when one party desires to triumph over another by any and every means, and to avenge itself on the vanquished with excessive cruelty.”

At first, this spirit of “any and every means” meant merely unprecedented political maneuvers and tactics. But as small deviations from the unspoken rules, called mos maiorum — “the way of the elders” — proved effective, the deviations became increasingly more extreme and treated as a necessary risk on the way to great rewards. The Greek historian Velleius Paterculus later wrote: “Precedents do not stop where they begin . . . no one thinks a course is base for himself which has proven profitable to others.”

Soon enough mere fraud, corruption and bribery devolved to armed street gangs literally fighting in the streets. These fights exposed the sad reality that all political power ultimately rests on brute force. A generation later, Pompey the Great would snap at magistrates who challenged him: “Cease quoting laws to those of us with swords.” Eventually all pretense of civility was dropped and Rome was engulfed by a series of destructive civil wars that destroyed the republic once and for all.

It did not have to be this way. After the imperial triumph of 146 B.C., reform was necessary. Had the Senate acted with foresight in the 130s and 120s, the republic might not have fallen a century later. Julius Caesar and Augustus both introduced a raft of reforms designed to do by autocratic fiat what the once-cooperative republican government had failed to achieve. Far from resisting such an autocratic takeover, many Roman citizens were thrilled the deadlock was broken and relief was on the way. One can only hope that we do not repeat the mistakes of history.