The Growth of Rome

How Ancient Rome Grew, Expanded Its Power, and Became Leader of Italy

Expansion of Ancient Rome
Map Showing the Expansion of Ancient Rome Click on the underlined for a link to a map you can enlarge.

From "The Historical Atlas," by William R. Shepherd, 1911

At first, Rome was just one small city-state in an area of Latin-speaking people (called Latium), on the west side of Italy's peninsula. Rome, as a monarchy (founded, according to legend, in 753 BCE), couldn't even keep foreign powers from ruling it. It started gaining strength from about 510 BCE (when the Romans threw out their last king) until the middle of the third century BCE. During this (early Republican) period, Rome made and broke strategic treaties with neighboring groups in order to help her conquer other city-states. In the end, after revising her battle tactics, weapons, and legions, Rome emerged as the undisputed leader of Italy. This quick look at the growth of Rome names the events leading to Rome's domination over the peninsula.

Etruscan and Italic Kings of Rome

In the legendary beginning of its history, Rome was ruled by seven kings.

  1. The first was Romulus, whose ancestry is traced to Trojan (War) prince Aeneas.
  2. The next king was a Sabine (a region of Latium northeast of Rome), Numa Pompilius.
  3. The third king was a Roman, Tullus Hostilius, who welcomed the Albans into Rome.
  4. The fourth king was Numa's grandson, Ancus Martius. After him came the 3 Etruscan kings:
  5. Tarquinius Priscus;
  6. His son-in-law Servius Tullius;
  7. Tarquin's son, the last king of Rome, known as Tarquinius Superbus or Tarquin the Proud.

The Etruscans were based in Etruria, a large area of the Italic peninsula to the north of Rome.

The Growth of Rome Starts: Latin Alliances

The Romans expelled their Etruscan king and his relatives peacefully, but soon thereafter they had to fight to keep them out. By the time the Romans had defeated the Etruscan Porsenna, at Aricia, even the threat of Etruscan rule of the Romans had reached its end.

Then the Latin city-states, but excluding Rome, banded together in an alliance against Rome. While they battled each other, the Latin allies suffered attacks from the mountain tribes. These tribes lived east of the Apennines, a long mountain range that separates Italy into an eastern and western side. The mountain tribes are presumed to have been attacking because they needed more arable land.

The Latins had no extra land to give the mountain tribes, so, in about 493 BCE, the Latins—this time including Rome—signed a mutual defense treaty that is called foedus Cassianum, which is Latin for "Cassian Treaty."

A few years later, in about 486 BCE, the Romans made a treaty with one of the mountain peoples, the Hernici, who lived between the Volsci and the Aequi, who were other eastern mountain tribes. Bound to Rome by separate treaties, the league of Latin city-states, the Hernici, and Rome defeated the Volsci. Rome then settled Latins and Romans as farmer/landowners in the territory.

Rome Expands Into Veii

In 405 BCE, the Romans began an unprovoked 10-year struggle to annex the Etruscan city of Veii. The other Etruscan cities failed to rally to the defense of Veii in a timely manner. By the time some of the Etruscan league of cities came, they were blocked. Camillus led the Roman and allied troops into victory in Veii, where they slaughtered some Etruscans, sold others into enslavement, and added land to the Roman territory (ager publicus), much of it given to Rome's plebeian poor.

  • Latin League
  • Veientine Wars
  • Battle of Lake Regillus
  • Coriolanus

Temporary Setback: The Sack of the Gauls

In the fourth century BCE, Italy was invaded by the Gauls. Although Rome survived, thanks in part to the noisily famous Capitoline geese, the Romans' defeat at the Battle of the Allia remained a sore spot throughout Rome's history. The Gauls left Rome only after they were given vast quantities of gold. Then they gradually settled down, and some (the Senones) made alliances with Rome.

Rome Dominates Central Italy

Rome's defeat made other Italic cities more confident, but the Romans didn't just sit back. They learned from their mistakes, improved their military, and fought off Etruscans, Aequi, and Volsci during the decade between 390 BCE and 380 BCE. In 360 BCE, the Hernici (Rome's former non-Latin league ally who had helped defeat the Volsci), and the cities of Praeneste and Tibur allied themselves against Rome, unsuccessfully: Rome added them to its territory.

Rome forced a new treaty on her Latin allies making Rome dominant. The Latin League, with Rome at its head, then defeated the league of Etruscan cities.

In the middle of the fourth century BCE, Rome turned toward the south to Campania (where Pompeii, Mt. Vesuvius, and Naples are located) and the Samnites. Although it took until the beginning of the third century, Rome did defeat the Samnites and annexed the rest of central Italy.​

Rome Annexes Southern Italy

Finally, Rome looked to Magna Graecia in southern Italy and fought King Pyrrhus of Epirus. While Pyrrhus won two battles, both sides fared badly. Rome had an almost inexhaustible supply of manpower (because it demanded troops of its allies and conquered territories). Pyrrhus pretty much only had those men he had brought with him from Epirus, so the Pyrrhic victory turned out to be worse for the victor than the defeated. When Pyrrhus lost his third battle against Rome, he left Italy, leaving southern Italy to Rome. Rome was then recognized as supreme and entered into international treaties.

The next step was to go beyond the Italic peninsula. 

Source: Cary and Scullard.


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Gill, N.S. "The Growth of Rome." ThoughtCo, Feb. 16, 2021, Gill, N.S. (2021, February 16). The Growth of Rome. Retrieved from Gill, N.S. "The Growth of Rome." ThoughtCo. (accessed June 4, 2023).