In 400 BC Rome was one city among many in central Italy. By 146 BC it controlled the western Mediterranean and dominated the Greek east. The speed of this rise puzzled the Greek historian Polybius, who set out to explain how "almost the whole inhabited world was conquered and brought under the dominion of the single city of Rome, and that too within a period of not quite fifty-three years" (translated by Evelyn Shuckburgh, 1889). His answer, and ours, involves alliances, manpower and a tolerance for losses that stunned Rome's enemies.
Conquering Italy
Between about 340 and 264 BC Rome brought the Latins, Samnites, Etruscans and the Greek cities of southern Italy under its control. The method mattered more than the battles. Defeated Italian communities usually became allies who owed Rome soldiers rather than tribute. They kept their own local governments, and some received partial or full Roman citizenship. Rome also planted colonies of settlers at strategic points and linked them with roads. The network gave Rome an enormous pool of manpower: it could lose an army and raise another, which no rival could match.
Carthage
Carthage was a wealthy city in North Africa, founded by settlers from Phoenicia on the coast of the eastern Mediterranean. It had a great navy and trading posts across Sicily, Sardinia and Spain, and it relied heavily on paid mercenaries, while Rome fought with citizen and allied levies. The two powers had signed treaties for centuries. They came to blows over Sicily, which lay between them.
The First Punic War, 264 to 241 BC
The wars are called Punic from the Latin word for Phoenician. The first was fought mainly in and around Sicily. Rome had almost no navy, so it built one, reportedly copying a wrecked Carthaginian warship, and fitted its ships with a boarding bridge, the corvus, that let Roman soldiers fight at sea almost as if on land. Rome lost whole fleets to storms but kept building. Victory in the First Punic War gave Rome Sicily, its first overseas province.
Hannibal and the Second Punic War, 218 to 201 BC
The Carthaginian general Hannibal Barca carried the next war into Italy. Hannibal marched from Spain over the Alps into Italy in 218 BC, bringing war elephants. He destroyed Roman armies at the Trebia River and Lake Trasimene, and at Cannae in 216 BC Hannibal encircled and destroyed a much larger Roman army, killing perhaps 50,000 Romans and allies in a single day (ancient figures vary). Then something surprising failed to happen. Most of Rome's allies in central Italy stayed loyal, Rome refused to negotiate, and Hannibal lacked the siege equipment to take the city.
Rome adapted. Quintus Fabius Maximus avoided pitched battles and wore Hannibal down by shadowing his army, earning the nickname Cunctator, the Delayer; a "Fabian strategy" still means winning through patience. Meanwhile the young Publius Cornelius Scipio took the war to Spain and then to Africa. Scipio defeated Hannibal at Zama, in North Africa, in 202 BC, earning the name Africanus, and Carthage gave up its fleet and its overseas empire.
The Third Punic War and the year 146 BC
Carthage recovered economically, and some Romans could not bear it. The senator Cato the Elder, Plutarch says, ended his speeches by declaring that Carthage must be destroyed. In 149 BC Rome provoked a final war, and in 146 BC Roman forces razed Carthage, killed or enslaved its people and turned its territory into the province of Africa. That same year Rome sacked the Greek city of Corinth.
Running an empire
Provinces were governed by former magistrates who held command for a year or so and often used it to get rich. Taxes in many provinces were collected by private contractors called publicani, who bid for the right and kept whatever they could squeeze out above the contract price. Trials for extortion became a regular part of Roman politics. Defenders of Roman expansion, ancient and modern, stress that Rome often fought at the invitation of allies, brought roads and order, and eventually shared its citizenship. Critics, including some Romans, called it plunder. In a speech the historian Tacitus composed for the Caledonian leader Calgacus, the Romans are accused: "To robbery, slaughter, plunder, they give the lying name of empire; they make a solitude and call it peace" (translated by Church and Brodribb, 1877).
Worked example: why Cannae did not end Rome
Cannae is still studied in military academies as a near perfect battlefield victory, yet Hannibal lost the war. Apply the ideas above. Hannibal's plan depended on breaking Rome's alliance network: he released captured Italian allies without ransom, hoping their cities would defect. Some did, including Capua and much of the south. But the core of central Italy held, because those communities kept their own local rule, shared in Roman success and had Roman colonies planted among them. Rome could therefore keep raising legions, and Fabius's delaying strategy bought time for that advantage to work. The lesson Polybius drew was that institutions and alliances, more than single battles, decide long wars. A modern reader might add a darker point: Rome's willingness to absorb tens of thousands of deaths without negotiating was a strength in war, and also a sign of how much such a state could demand of its people.