What changes in the ancient Roman military did Augustus make to help stablize the empire?

Answer 1

Augustus did not make changes to the structure of the legions, which were already formidable fighting machines, or the Roman military in general. The military was one of his power bases, he controlled it. During the civil war against Mark Anthony, Augustus already controlled the majority of the legions. The forces of Mark Antony and Cleopatra were similar in size, but many of the troops were Cleopatra's Egyptians. Many of Antony's troops defected to him during the war. Augustus pardoned the remaining ones in exchange for loyalty. Moreover, he emerged as the supreme military leader and Roman soldiers were loyal to military leaders. Augustus restored stability in an empire which was left exhausted and shattered by 20 years of civil wars by becoming an absolute ruler. His tight grip on power ensured stability. His control over the legions was a crucial part of this.

Augustus restored the professionalism and pay system of the army, which had broken down during the civil wars. He increased the pay of the soldiers. He reduced the size of the army by more than half. It had swollen to financially unsustainable levels because of heavy recruitment by the commanders of the various opposing sides of the civil wars who levied new legions. He pensioned off many soldiers through the agraria missio, the grant of a plot of land to farm. A lot of land in Italy was expropriated for allocation to veterans. This also aided Augustus' effort to try to repopulate Italy, whose population had been decimated by the wars.

Augustus' control of the army played an important role in the First Settlement with the senate (27 BC). Although constitutionally only ex-senators could be provincial governors, Augustus was given the governorship of the frontier provinces with a 10 year mandate to "pacify" them, and the senate retained control of the core provinces. Since most of the legions were stationed in the frontier provinces, this gave Augustus control of 20 legions, while the senate controlled only 5 of them. Thus, the settlement institutionalised Augustus' military power.

Augustus' biggest change to the military was the creation of new auxiliary troops and the Praetorian Guard.

Previously the auxiliary troops had been composed of Rome's Italian allies. They were troops of non-Romans which supported the Roman legions and provided the bulk of the cavalry. In the 3rd century BC they provided 60% of the military manpower available to Rome. Augustus instituted new auxiliary troops which were open to all non-Romans in the whole empire. They were structured along the lines of the Roman legion, but the pay was lower. The careers of these soldiers lasted 25 years. On retirement they were entitled to a grant of a pot of land to farm (agraria missio) or a sizable lump sum of money (numnaria missio) like the Roman legionaries. They also received Roman citizenship. The size of the new auxiliary troops came to equal that of the Roman legions.

The Praetorian Guard was the imperial guard. The term praetoran originated from the hut of the commander of the army in the field, the praetor. These commanders recruited a private force from the ranks to protect them and their huts. This force then developed into a cohort, the cohors praetoria. Julius Caesar developed a whole legion (the Legio X Equestris) which he levied personally, into his own legion. It was his most trusted force and an important part of his power base.

Augustus saw the need for his protection in the volatile politics of the city of Rome. To retain the pretence that his regime was republican, he recruited only five cohorts of 500 men. Only three cohorts and small squadrons (turmae) of 30 cavalry, which discretely patrolled his palace and Rome's main buildings, were stationed in Rome. The others were stationed in towns near Rome. Augustus later increased the size of the cohorts to 1,000 men.

After Augustus the Praetorian Guard become a powerful political force in Rome. During the reign of Tiberius the whole force was stationed at the Castra Praetoria (the barracks of the Praetorian Guard) just outside Rome. The Praetorian Guard was part of the conspirators who killed the emperor Caligula. It installed Claudius to the imperial title in defiance to the senate. Galba bribed this guard to become emperor, which then killed him when he failed to pay them and transferred their allegiance to Otho who, in turn, had bow to their demand to be given the right to appoint their own praetors to retain their loyalty. The next emperor, Vitellius, disbanded the guard and created a new one. The dismissed soldiers supported the power bid of Vespasian, who became the next emperor.