The richer principes, the second line of soldiers, could afford lorica hamata but they were sometimes seen wearing the cheaper cuirasses. Regular annual conscription remained in force and continued to provide the core of legionary recruitment, but an ever-increasing proportion of recruits were volunteers, who signed up for 16-year terms as opposed to the maximum 6 years for conscripts. This page was last changed on 9 December 2014, at 21:10. When the kings were replaced by two annually elected praetores in c. 500 BC, the standard levy remained of the same size, but was now divided equally between the Praetors, each commanding one legion of 4,500 men. The size of the army in the late Roman Empire was about 128,000 – 179,200 men. Legions were divided into ten groups called cohorts consisting of around 480 soldiers. Each of which would have different roles in the military. It is believed that at one point the Roman army had over one million soldiers. As a large, disciplined and skilled force of fit men, they played a crucial role in the construction of a province's Roman military and civil infrastructure: in addition to constructing forts and fortified defences such as Hadrian's Wall, they built roads, bridges, ports, public buildings, entire new cities (Roman colonies), and also engaged in large-scale forest clearance and marsh drainage to expand the province's available arable land. The term "late Roman army" is often used to include the East Roman army. For centuries the ancient Roman army dominated the battlefield. However, these native units were not integrated with the legions, but retained their own traditional leadership, organisation, armour and weapons. This had increased to a peak of 33 legions of about 5,500 men each (c. 180,000 men in total) by 200 AD under Septimius Severus. However, in 212, the emperor Caracalla granted Roman citizenship to all the empire's inhabitants.

Iuniores of the highest social classes (equites and the First Class of commoners) provided the legion's cavalry, the other classes the legionary infantry. Legionary centurions, the equivalent of mid-level commissioned officers, were organised in an elaborate hierarchy. Any poorer citizen, called Capite Censi would have no weapons. Legions were led by a commander called a Legate. Numbers fluctuated according to circumstances and are largely unknown. By c. 1350, following a destructive civil war and the outbreak of the Black Death, the Empire was no longer capable of raising troops and the supplies to maintain them. The Roman army could march up to 40 km a day! Life expectancy in Ancient Rome was just 20-30 years. As all-citizen formations, and symbolic guarantors of the dominance of the Italian hegemony,[citation needed] legions enjoyed greater social prestige than the auxilia.

Auxiliaries, who served a minimum term of 25 years, were also mainly volunteers, but regular conscription of peregrini was employed for most of the 1st century AD. Until the Roman military disaster of 390 BC at the Battle of the Allia, Rome's army was organised similarly to the Greek phalanx. The Roman army of the late Republic (88–30 BC) marks the continued transition between the conscription-based citizen levy of the mid-Republic and the mainly volunteer, professional standing forces of the imperial era. The early Roman army was based on an annual levy. By the end of Augustus' reign, the imperial army numbered some 250,000 men, equally split between legionaries and auxiliaries (25 legions and c. 250 auxiliary regiments). The 3rd and 4th centuries saw the upgrading of many existing border forts to make them more defensible, as well as the construction of new forts with much higher defensive specifications. At the beginning of the Komnenian period, the Byzantine army was reduced to a shadow of its former self: during the 11th century, decades of peace and neglect had reduced the old thematic forces, and the Battle of Manzikert in 1071 had destroyed the professional tagmata, the core of the Byzantine army.

Senior officers were paid enormous salaries, multiples of at least 50 times basic. Elders, vagrants, freedmen, slaves and convicts were excluded from the military levy, save in emergencies.