After the civil wars which brought Augustus to power, on the winning side alone, 60 legions stood combat-ready.Augustus decided to retain 28, while the remainder would be demobilized and settled in the colonies.By this act, the west's first standing army of 150'000 legionaries and a similar number of auxiliaries was created. Length of service was set at sixteen years, later it was increased to twenty.Though his army of 28 legions Augustus made sure to quickly spread across the far reaches of the empire, with all the legions being posted both far away from Rome as well as as far away as possible from each other.It expressed Augustus' distrust of soldiers and of ambitious men who might rouse them against him.By keeping the armies close to the borders their energies would be directed outward, toward foreign enemies; and keeping them far from each other would ensure that no overwhelming force could be assembled which might threaten the throne.While this caution, right after the civil war, was understandable, Augustus' arrangements would long outlive him.Augustus disposition of the legions was matched by his manipulation of the provinces. Of these he retained the most powerful under his direct power on the grounds that they were insecure, either with enemies on their borders or were themselves capable of rebellion. But his real purpose was that he alone should have arms and maintain soldiers. In short, Augustus kept the outer, returning the inner provinces to the Senate. It was a muted way of assuring himself commander-in-chief, for the army would be stationed only in the outer provinces which would be governed and administered by the emperor's appointees. This meant that the frontier would be under direct imperial authority, establishing for the emperor a hold over foreign affairs and decisions of peace and war.The division of territory into 'Senate's share' and 'Caesar's share' was accompanied by a ban on senators even visiting a frontier province without imperial permission.It was clear from this that Augustus saw the Senate as one of the likeliest sources from which to expect a challenge to his position.To this one must add, that to Augustus (as well as to later Caesars) the Senate, with its centuries of experience, remained indispensable in running the empire. 
The East of the empire gave no trouble. The small dependent kingdoms still surviving in Asia Minor (Turkey) were peacefully and gradually absorbed into the Roman provincial system. Parthia under king Phraates had no desire to challenge Rome. The unavenged disaster of Carrhae in 53 BC however had always rankled in the Roman mind. So when in 20 BC a demand was made by Rome, emphasized by a military demonstration of force along the border, for the return of the captives and most importantly for the legionary standards, which had been in Parthian possession since the disastrous defeat of Crassus over thirty years earlier. King Phraates wisely gave way, avoiding war against a newly united foe, increasing in strength. The standards were returned to Rome without a fight. An achievement which won Augustus high praise.
The East of the empire gave no trouble. The small dependent kingdoms still surviving in Asia Minor (Turkey) were peacefully and gradually absorbed into the Roman provincial system. Parthia under king Phraates had no desire to challenge Rome. The unavenged disaster of Carrhae in 53 BC however had always rankled in the Roman mind. So when in 20 BC a demand was made by Rome, emphasized by a military demonstration of force along the border, for the return of the captives and most importantly for the legionary standards, which had been in Parthian possession since the disastrous defeat of Crassus over thirty years earlier. King Phraates wisely gave way, avoiding war against a newly united foe, increasing in strength. The standards were returned to Rome without a fight. An achievement which won Augustus high praise.
By 19 BC Agrippa had assured the submission of the Spanish tribes. But a German incursion across the Rhine in 16 BC defeated a Roman commander, Lollius, and called for the temporary presence of Augustus at the front, where he left the command in the hands of his stepson Drusus.
In 12 BC Agrippa died and with him Augustus lost his most obvious heir. For a while Augustus hoped for Gaius or Lucius, both sons of Agrippa to succeed him, but as they both died his choice somewhat reluctantly fell on Tiberius, the son by his wife out of a previous marriage.Then followed a conquest of Germany, initially to the Elbe. At first it was led by Drusus, who died on campaign. He was succeeded by Tiberius who had established Roman supremacy over Pannonia and Noricum.Sixteen years' struggle in mire and forest, amphibious landings and spectacular marches were rewarded with a succession of victories. A bold project, sometimes referred to as the 'Bohemian Plan', was mooted as a culminating blow. Tiberius would cross the Danube heading north, snip off what is now the western end of the Czech Republic, descend into the German plain and join hands with an army group advancing eastwards from the Rhine. The so-called 'Bohemian Plan' may have only been meant as one step in a much larger offensive.Rome, of course, virtually unbeaten so far and inexorably rising to conquer the word, by now virtually understood the rule of the world its birthright.But none of these grand schemes would be implemented. Shortly before commencement of operations, a revolt erupted in Tiberius' rear and spread rapidly across the Balkans. To quell it required almost half of Rome's fighting strength, to become tied up for three years in a mountain war.Meanwhile it was deemed that Northern Germany, west of the Elbe was sufficiently pacified. P. Quintillius Varus was entrusted as governor of the province. Though Germany was not ready for Roman civilization. In AD 9 disaster struck an empire which until then had virtually met no opponent capable of halting its rise to supreme power.Under the command of Varus three legions and three cavalry squadrons marched through the Teutoburger Wald (Saltus Teutoburgiensis) The German tribe, the Cherusci, under their leader known to the Romans as Arminius, had learnt their lesson.In open terrain, with room to manoeuvre, the Roman army was literally unbeatable. But in the middle of a forest, it was vulnerable. The trap was sprung and three entire legions were annihilated. Arminius' victory was a major turning point in the history of the Roman Empire. If Romans had previously marched as far as the Elbe, and even if they could do so in future, then this proved that they would never ever really rule any territory north of the Rhine and the Danube. - Rome had alas met its match in the barbarians of northern Europe.Though it was a costly lesson for Rome. Three legions had been annihilated. Varus and his staff committed suicide. It was to be remembered by the Romans as the 'Varian disaster'.Tiberius thereafter still could march his legions through Germany almost unhindered, in fact he did so. But not to subdue it and conquer it. For this, one now understood, was beyond Roman power.Tiberius was recalled from his task of restoring Roman authority in Germany. Instead command was left in the hands of Germanicus, who was to be highly popular with the legions, in contrast to the almost despised Tiberius.Had Germanicus had any serious political ambitions he would certainly have become a formidable opponent to any future emperor. Yet, Germanicus was loyal and a devoted soldier.
Alas, Augustus went out with advice to his successors that the empire should be kept within its existing boundaries. This was an astonishing turn of events. The imperialist had recanted. Rome could not expand indefinitely. He had in office learned of the problems facing an empire of this scale and appreciated the difficulties in holding it together.Any further expansion in the eyes of the elderly Augustus would take the empire beyond being practically governable.Also, the Mediterranean part of Europe, Africa and Asia, which Rome now ruled had been developed prior to Roman occupation. There was roads, town, cities. What prize was there to win, defeating the barbarian hordes of the north. Augustus ultimate conclusion from the Varian Disaster was that only civilized territories were worth the blood of Roman legionaries.His advice would have demanded a change in attitude by all Rome - to defend, not to conquer. Rome however, the she-wolf with her mighty legions, was not yet ready for such advice.
Alas, Augustus went out with advice to his successors that the empire should be kept within its existing boundaries. This was an astonishing turn of events. The imperialist had recanted. Rome could not expand indefinitely. He had in office learned of the problems facing an empire of this scale and appreciated the difficulties in holding it together.Any further expansion in the eyes of the elderly Augustus would take the empire beyond being practically governable.Also, the Mediterranean part of Europe, Africa and Asia, which Rome now ruled had been developed prior to Roman occupation. There was roads, town, cities. What prize was there to win, defeating the barbarian hordes of the north. Augustus ultimate conclusion from the Varian Disaster was that only civilized territories were worth the blood of Roman legionaries.His advice would have demanded a change in attitude by all Rome - to defend, not to conquer. Rome however, the she-wolf with her mighty legions, was not yet ready for such advice.
