Rome represented a unique fusion of Greek-style citizenship with Macedonian-style militarism. The result was the most dynamic imperialist state in the ancient world.

Rome evolved from an Iron Age village in the 9th century BCE (before the common era) into a Latin chieftain’s hillfort during the 8th century. It was then re-founded as a small town by Etruscan invaders in the mid to late 7th century, and thereafter ruled by a dynasty of Etruscan kings until about 510 BCE.

The last of the kings was overthrown in an aristocratic revolution. The succeeding two centuries were characterised by both internal class struggle and external imperial expansion. These two processes were closely linked.

The internal struggle – ‘the Struggle of the Orders’ – pitted ‘patricians’ against ‘plebeians’. The former constituted an hereditary landowning aristocracy who enjoyed exclusive control over the state apparatus. Only patricians were admitted to the Senate, the ruling aristocratic assembly, and only patricians could hold senior ‘magistracies’, the top government posts.

Most plebeians were ordinary citizen-farmers. As in the Greek city-states, small farmers, with no margin against hard times, frequently got into debt. The rights of creditors were protected by laws enacted by patrician senators and enforced by patrician magistrates. Debt was the primary mechanism by which big estates were enlarged at the expense of small farms.

A minority of plebeians were better-off. Some were seriously rich. But these plebeians were still excluded from political power. The plebeian movement was therefore a class alliance between plebeian nobles and plebeian masses. Its principal weapon was ‘secession’.

Secession was a military mass-strike. Like the citizen-farmers of Greek city-states, the Roman plebs formed the city militia – the legio or ‘levy’. They periodically refused to fight in order to press social and political demands.

The Greek masses had taken revolutionary action and won full-blooded democracy. The Roman masses never succeeded in overthrowing the Senate. But they did make huge gains, and the cumulative effect was a radical redistribution of power within Roman society.

Rich plebeians were admitted to the Senate and senior magistracies. The mass of plebeians won effective veto powers. New laws had to be approved by the Assembly of the Plebs (a civic body), and any decision to go to war by the Assembly of the Centuries (a military body). Unpopular proposals could be blocked by new magistrates called ‘Tribunes of the Plebs’.

The Struggle of the Orders ended with a class compromise and a mixed constitution. The ruling class was not overthrown, but its ranks were opened to newcomers, and its political power was constrained. State action became contingent on popular consent.

The property of small farmers was protected against tax and debt. This limited the ability of big landowners to enrich themselves at the expense of fellow citizens. Instead, the ambition of the Roman aristocracy was directed against foreign enemies.

The Roman aristocracy was highly competitive. Top families competed for senior state posts. The rewards were power, prestige, and rich pickings.

Wealth was the means rather than the end: aristocrats required wealth in order to accumulate political power. Rival factions built up retinues of dependants and clients through patronage. They amassed supporters and consolidated voting blocs through bribery.

Families that failed to accumulate power fell into decline. Membership of the aristocratic classes (senators and equestrians) depended increasingly on wealth. Patronage, public office, and the political power struggle became essential to maintaining class status.

Plebeian resistance to exploitation determined the form of intra-aristocratic competition. On the one hand, plebeian support became essential to factional power. On the other, plebeian landownership limited opportunities for amassing wealth by enlarging existing estates.

War and conquest offered an alternative. Victory over foreign enemies meant booty (especially bullion), captives (who became slaves), and land (to create new farms and estates). Some was shared with ordinary citizen-legionaries, who therefore had an interest in voting for war and fighting effectively. But the lion’s share went to the state and its senator-generals.

So Rome became a predatory imperial system of robbery with violence. Instead of accumulating surplus by raising the rate of exploitation at home, the Roman ruling class seized by force the surplus, labour, and means of production controlled by foreign ruling classes.

During the 5th and 4th centuries BCE, the Romans conquered peninsular Italy. During the 3rd, they fought two major wars against the Carthaginian Empire for control of the Western Mediterranean. During the 2nd, they fought two major wars against the Kingdom of Macedonia for control of Greece.

The process of military accumulation was self-feeding. The surpluses seized in one war provided the resources to launch the next. Defeated ruling classes were ‘Romanised’: they were granted Roman citizenship, encouraged to adopt Roman elite culture, and offered a share in future Roman conquests. This ensured a steady supply of new recruits for the expanding legions.

After the Struggle of the Orders, during the 3rd and 2nd centuries BCE, Rome was stable at home, but relentlessly aggressive abroad. The one depended on the other: imperial surpluses funded social peace.

Rome had grown from a small Latin city-state in the late 7th century BCE to the most powerful empire of antiquity by the late 2nd century.

Iron Age technology generated the huge surpluses necessary to construct the mega imperial polities of the first millennium BCE – Achaemenid Persia, Mauryan India, Ch’in China, the Macedonian Successor kingdoms, and the Roman Empire.

But Roman imperialism had an exceptional dynamism and durability. At the Battle of Gaugamela in 331 BCE, the culmination of a four-year blitzkrieg campaign, Alexander the Great destroyed the Persian Empire.

At the Battle of Cannae in 216 BCE, Hannibal of Carthage inflicted an equally shattering battlefield defeat on the Roman Republic. But Rome refused to surrender and eventually triumphed.

The critical difference was the social base of Roman imperialism. Achaemenid Persia levied tribute on subject peasants to pay professional soldiers. The army of the Roman Republic was a militia of free citizens. The Roman peasantry was not only numerous, but, unlike the Persian peasantry, it had a stake in the system.

The Romans lost 80,000 men at Cannae. But their manpower reserves are estimated to have been 700,000 infantry and 70,000 cavalry, and both aristocracy and peasantry had an interest in continuing the struggle.

The superiority of the Roman imperial polity was to be tested again in the great crisis of the Late Republic (133-30 BCE). To this we turn next