Slovakia in the Roman era
The reign of Augustus (27 BC - 14 AD) began a long period known as the Pax Romana, or Roman peace. Despite continuous wars on the frontiers, and one year-long civil war over the imperial succession, the Mediterranean world remained at peace for more than two centuries. Augustus enlarged the empire dramatically, annexing Egypt, Dalmatia, Pannonia, and Raetia, expanded possessions in Africa, and completed the conquest of Hispania.
By the end of his reign, the armies of Augustus had conquered the Alpine regions of Raetia and Noricum (modern Switzerland, Bavaria, Austria, Slovenia), Illyricum and Pannonia (modern Albania, Croatia, Hungary, Serbia, etc.).
Roman army
During this period the Republican system of citizen-conscription was replaced by a standing professional army of mainly volunteers serving standard 20-year terms (plus 5 as reservists), although many in the service of the 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 – AD 14).Regular annual conscription of citizens was abandoned and only decreed in emergencies (e.g. during the Illyrian revolt 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 AD 200 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. The "auxilia" consisted, under Augustus, of about 250 regiments of roughly cohort size, that is, about 500 men (in total 125,000 men, or 50% of total army effectives). Under 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, and almost all the army's cavalry (both armoured and light), and archers and slingers.