The military of ancient Rome, according to Titus Livius, one of the more illustrious historians of Rome over the centuries, was a key element in the rise of Rome over “above seven hundred years” from a small settlement in Latium to the capital of an empire governing a wide region around the shores of the Mediterranean, or, as the Romans themselves said, ‘’mare nostrum’’, “our sea.” Livy asserts
- ”... if any people ought to be allowed to consecrate their origins and refer them to a divine source, so great is the military glory of the Roman People that when they profess that their Father and the Father of their Founder was none other than Mars, the nations of the earth may well submit to this also with as good a grace as they submit to Rome's dominion.”
Titus Flavius Josephus, a contemporary historian, sometime high-ranking officer in the Roman army, and commander of the rebels in the Jewish revolt, describes the Roman people as if they were "born ready armed." At the time of the two historians, Roman society had already evolved an effective military and had used it to defend itself against the Etruscans, the Italics, the Greeks, the Gauls, the maritime empire of Carthage, and the Macedonian kingdoms. In each war it acquired more territory until, when civil war ended the Roman Republic, nothing was left for the first emperor, Augustus, to do except declare it an empire and defend it.