Until its defeat at Allia, the Roman army had fought as the Greeks fought, in a tight phalanx formation. This should not be confused with the Macedonian phalanx which is an infantry unit that wielded a long double-handed, 20-foot-long, spear called a sarissa rather than a traditional hoplite spear (approximately 6 feet long). The military reforms are associated with the name of Lucius Furius Camillus, the dictator who presumably took the Etruscan city of Veii, defeated the Volsci and Aequi and expelled the Gauls from Rome and from Latium.

It should be kept in mind that Roman soldiers were already being paid for their service from state coffers. This allowed them to pursue a year-round military strategy than one that was seasonal and tied to agricultural rhythms.

The roman army was reorganized along the following lines: