the Roman Empire would serve as many as 30 to 40 years on active duty, as established by the first Roman emperor, Augustus (sole ruler 30 BC–14 AD). Regular annual conscription of citizens was abandoned and only decreed in emergencies (e.g. during the Illyrian revolt of 6–9 AD). Under Augustus, there were 28 legions, consisting almost entirely of heavy infantry, with about 5,000 men each (total 125,000). 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. Legions continued to recruit Roman citizens, mainly the inhabitants of Italy and Roman colonies, until 212. Legions were flanked by the auxilia, a corps of regular troops recruited mainly from peregrini, imperial subjects who did not hold Roman citizenship (the great majority of the empire's inhabitants until 212, when all were granted citizenship). 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. Under Augustus, the auxilia consisted of about 250 regiments of roughly cohort size, that is, about 500 men (in total 125,000 men, or 50% of the total army). Under Septimius Severus, the number of regiments increased to about 400, of which about 13% were double-strength (250,000 men, or 60% of total army). Auxilia contained heavy infantry equipped similarly to legionaries, almost all of the army's cavalry (both armoured and light), archers and slingers. Later Roman army (284–476 AD) continuing as East Roman army (476–641 AD) The Late Roman army period stretches from (284–476 AD and its continuation, in the surviving eastern half of the empire, as the East Roman army to 641). In this phase, crystallised by the reforms of the emperor Diocletian (ruled 284–305 AD), the Roman army returned to regular annual conscription of citizens, while admitting large numbers of non-citizen barbarian volunteers. However, soldiers remained 25-year professionals and did not return to the short-term levies of the Republic. The old dual organisation of legions and auxilia was abandoned, with citizens and non-citizens now serving in the same units. The old legions were broken up into cohorts or even smaller units. At the same time, a substantial proportion of the army's effectives were stationed in the interior of the empire, in the form of comitatus praesentales, armies that escorted the emperors. Middle Byzantine army (641–1081 AD) The