Military of ancient Rome

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The military of ancient Rome was one of largest pre-modern professional standing armies that ever existed. At its height, protecting over 7,000 kilometers of border and consisting of over 400,000 legionaries and auxiliaries, the army was the most important institution in the Roman world. According to the Roman historian Livy, the military was a key element in the rise of Rome over "above seven hundred years"^[1] 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.^{[citation needed]}

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 readily armed".^[2] 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 the civil war ended the Roman Republic, nothing was left for the first emperor, Augustus, to do except declare it an empire and defend it.^{[citation needed]}

The role and structure of the military were then altered during the empire. It became less Roman, the duties of border protection and territorial administration being more and more taken by foreign mercenaries officered by Romans. When they divided at last into warring factions the empire fell, unable to keep out invading armies.

During the Roman Republic, the function of the military was defined as service to the "Senatus Populusque Romanus" – an agency designated by SPQR on public inscriptions. Its main body was the senate, which met in a building still extant in the forum of Rome. Its decrees were handed off to the two chief officers of the state, the consuls. They could levy from the citizens whatever military force they judged was necessary to execute such decree. This conscription was executed through a draft of male citizens assembled by age class. The officers of the legion were tasked with selecting men for the ranks. The will of the SPQR was binding on the consuls and the men, with the death penalty often assigned for disobedience or failure. The men were under a rigorous code, known now for its punitive crucifixion.

The consular duties were of any type whatever: military defense, police work, public hygiene, assistance in a civil disaster, health work, agriculture, and especially the construction of public roads, bridges, aqueducts, buildings, and the maintenance of such. The soldiers were kept busy doing whatever service needed to be done: soldiering, manning vessels, carpentry, blacksmithing, clerking, etc. They were trained as required, but also previous skills, such as a trade, were exploited. They were brought to the task and were protected by the authority of the state.

The military's campaign history stretched over 1300 years and saw Roman armies campaigning as far east as Parthia (modern-day Iran), as far south as Africa (modern-day Tunisia) and Aegyptus (modern-day Egypt) and as far north as Britannia (modern-day England, southern Scotland, and Wales). The makeup of the Roman military changed substantially over its history, from its early days as an unsalaried citizen militia to a later professional force, the Imperial Roman army. The equipment used by the military altered greatly in type over time, though there were very few technological improvements in weapons manufacture, in common with the rest of the classical world. For much of its history, the vast majority of Rome's forces were maintained at or beyond the limits of its territory, to either expand Rome's domain or protect its existing borders. Expansions were infrequent, as the emperors, adopting a strategy of fixed lines of defense, had determined to maintain existing borders. For that purpose, they constructed extensive walls and created permanent stations that became cities.