Roman armies

Traditionally, Servius Tullius (see rex) made the first attempt to channel the resources of the Roman state into military organization by dividing the citizens into wealth groups, so that the weapons they could afford determined their military role, with the richest serving as cavalry. Below these groups were the capite censī (‘assessed by a head‐count’)—men with no property, who were excluded from the army. Military service, therefore, although integral to the duties of citizenship, was also a privilege. This organization of the citizens probably emerged gradually and not through the act of an individual. By c.400 bc a small allowance had been introduced for each soldier to help pay his expenses on active service. The body of infantry was called the legiō (‘levying’, legion) and by 311 had been divided into four legions; they were supported by contingents of Rome's Italian allies (socii) and subjects, grouped in formations comparable in size to the legions and commanded by Roman officers. Archers and other specialist fighters were supplied by mercenaries.

The Punic Wars stretched Roman manpower resources to the limit. The system of recruitment had been designed for a small city‐state fighting short annual campaigns in Italy. Rome now waged long wars, sometimes overseas, and after the defeat of Carthage in 201, began to acquire provinces that needed a permanent military presence. So, there was a reduction in the property qualification for military service. The annual levy selected citizens of military age (17–46), who were expected to serve for up to six consecutive campaigns but be available for enlistment for up to sixteen years, or ten years in the case of a cavalryman. The army was commanded by the chief magistrates, the consuls.

Throughout the 2nd cent. there was increasing discontent with the levy as Rome faced a series of foreign wars, and the property qualification was further reduced. Then in 107 the consul Marius extended this practice by accepting volunteers from the propertyless and had them equipped at the state's expense for the war in Africa (see jugurtha). Undoubtedly conscription along the normal lines still continued, but many volunteers probably chose to serve for sixteen years, and this contributed to the development of a professional, long‐term army. The consequences of the Social War (91–87) were also far‐reaching, since Rome's defeated Italian allies were absorbed into the citizen body, significantly increasing the reservoir of manpower. Non‐Italians now provided auxiliary forces of cavalry (see auxilia). But the state had no policy of granting appropriate discharge payments to its troops. Generals, often holding long‐term commands, used their reputation, and promises of generous benefits, to recruit men with whom they then built up a personal rapport. Increasingly soldiers owed their allegiance to their commander rather than to the Roman state, and became instruments of violent political change. The precedent set by Sulla in 88 of seizing power by military might was not to be expunged, and the republic succumbed to the rival mercenary armies of military dynasts.

Augustus united these disunited legions in loyalty to his person and created a fully professional, standing army. This was not revolutionary in itself, but his detailed provision for the troops' service conditions and emoluments (see aerarium; stipendium; veterans), the incorporation of the non‐citizen auxilia into the formal military structure, the establishment of a personal bodyguard (praetorians), the permanent policing of Rome (see cohortes urbanae), and the apportionment of legions and auxilia as permanent garrisons of individual provinces, shaped Roman military thinking until the 3rd cent. ad and made military organization an integral part of imperial policy. The most striking development in the command of the Roman army was that from the end of the 1st cent. ad onwards, the emperor, who in his nomenclature and public portrayal bore the attributes of a Roman general, took personal charge of all major campaigns.

[...]