The process of organizing the Roman army of the Empire period should undoubtedly be associated with the person of Octavian Augustus (30 BCE – 14 CE). Thanks to his actions the Roman army has become fully professional.
The first stage of the army reform was to demobilize too many legions that remained after the end of the civil war of 31-30 BCE. Of a total of approximately sixty legions fighting both under Octavian and on the Marcus Antony side, half have been disbanded. Twenty-eight legions remain on active. The soldiers of the legions that had been disbanded received ground in Italy and in the Roman provinces. They were also paid one-time severance payments. Octavian obtained funds for demobilization from his private funds.
Secondly, the soldiers of the twenty-eight legions were dismissed from service. Those legionaries who had been in service long enough were demobilized. They were also granted land and financial retirement benefits. In place of the veterans, new recruits began to be accepted. The conditions under which they were to serve gradually began to change as a result of successive reforms initiated by Octavian. The Roman Senate also actively participated in the process of these changes. And so already in 27 BCE senators passed a resolution granting people serving in Octavian’s bodyguard double the rate of pay than that which was paid to legionaries. Thanks to this, the soldiers of the Praetorian Guard (cohortes praetoriae), in addition to specifying the method of calculating the amount of their pay, thus received a kind of legal sanction to legally function within the Roman armed forces. Legionnaires, as the content of the resolution in question suggests, also had to have approved regular pay.
In 13 BCE another length-of-service reform was introduced. Octavian, after returning from Gaul, introduced the rule that the period of service for legionaries was to be 16 years, and for soldiers of the Praetorian Guard – 12 years. “active reserve” for four years. This meant that in the event of an emergency, these veterans were to report back to their units and take part in their assigned tasks.
In 5 CE the length of the service time has changed. From then on, the legionaries were to serve for 20 years and the praetorians for 16 years. The “active reserve” was extended by one year to five years. In 6 CE Octavian decided to carry out another reform related to the problem of material security for soldiers leaving the service. Veterans were to receive retirement benefits of 3000 denarii for legionaries and 5000 denarii for the Praetorian soldiers. These amounts were to be paid out by a specially created fund called the military treasury (aerarium militare). On his account, Octavian transferred a one-time grant in the amount of 170 million sesterces.
The permanent source of income for the military treasury was to be income from two taxes. The first was a 5% inheritance tax credited to persons who were not relatives of the testator. The second tax was the public sale fee in the amount of 1% of the value of the sold items. The aerarium militare was to be supervised by three collegiate officials who had previously held the office of praetor. Octavian also introduced a formal ban on marriages by soldiers while performing military service. Regular pay, time limits for service and retirement benefits were the three essential elements that created the status of the Legions and Praetorian Guard. From then on, the military service began to take on the hallmarks of a profession and the Roman army definitely ceased to function as a civic militia or mass mobilization.
Octavian Augustus’ military reforms did not extend to auxiliary troops (auxilia velauxiliares), which included non-Roman citizens of the Roman state (peregrini). Octavian Augustus, in addition to demobilizing some auxiliary units taking part in civil wars, did not specify the rules by which soldiers from these units were to perform their service. Only during the reign of the emperor Claudius (41 – 54 CE), it was agreed that they were to serve for 25 years. After leaving the service, each of the auxiliary soldiers was to receive Roman citizenship for himself, and his wife – if he would get married and have children in the future. An official form of confirmation of receipt of such a privilege has been introduced in the form of the so-called military diploma, issued in the name of the honoured person. For soldiers of auxiliares units, permanent pay and retirement benefits have been established.
Successive reforms supplemented or modified the shape of the Roman armed forces, adapting them to the changing situation of the state. They concerned both the issue of salary revaluation, changes in recruitment, the introduction of new types of units, building of permanent lines of defence, and generally modernizing the entire army.
During the rule of Flavius Vespasian (69-79 CE), men who came from Romanized Roman provinces began to be accepted into the legions more than ever before.
During the reign of Domitian (81-96 CE) there was an increase in the basic wages of soldiers. On his initiative, the construction of permanent lines of fortifications (limes) was started, which were to protect the borders of the Roman state on the Rhine.
Since the times of the Flavians, there have been cases of one-time granting of Roman citizenship to all soldiers of auxiliary troops (auxilia), which showed particular bravery.
Thanks to Hadrian (117 – 138 CE) the organizational framework was established for two new types of auxiliary departments. These were numeri and cunei, which first appeared at the end of the 1st century CE On Hadrian’s initiative, a rampart in Britain was built. He also allowed legions to replenish their ranks where they were stationed. Finally, it was during his reign that horse and foot auxiliaries began to arm themselves in the manner of Roman legionaries.
Antoninus Pius (138 – 161 CE) modified the principle of granting Roman citizenship to children of veterans of auxiliary units. From then on, their sons were to acquire civitas Romana on their own. On Pius’ command, the second line of fortifications was erected in Britain, named Antonin’s Wall.
In the nineties of the 2nd century CE Septimius Sever (193 – 211 CE) carried out a thorough modernization of the army. It consisted in increasing the number of departments in individual departments, modifying the existing recruitment rules and increasing the basic pay rates. Severus lifted the ban on getting married while in service. With his consent, the commanders of the legions could be people from the equites estate (praefecti legionis). Severus also introduced the rule that the sons of centurions would automatically become equites. It was also his merit that the enlistment to the legions was based only on the population of the province where the unit was stationed.
Since the time of Alexander Severus (222 – 235 CE) plots of land received not only by veterans but also by officers and soldiers serving on the border they could not be transferred to non-military persons. They were passed on to the sons of soldiers, as long as they also devoted themselves to military service.
During the reign of Gaul (253 – 268 CE), representatives of the senatorial state (ordo senatorius) were removed from office any officer positions in the military. Legati legionis have been replaced by Equestrian praefecti legionis. On his initiative, a mounted reserve army (Equites) was created.
In the 3rd century CE Diocletian (284 – 305 CE) split the Roman army into frontier troops (limatenei – ripenses) and field (palatini – comitatenses). It was probably also he who issued the decree that the sons of soldiers and veterans if they were physically capable, were also obliged to take up the soldier’s profession.