This is something I still don't really understand. I know all of the important historical facts, having read Heather and Goldsworthy: I know the Romans originally let the (later) Visigoths enter the Empire, that they didn't supply them properly, that the Goths at times also fought for the Empire, the disaster of Adrianople etc.
Yet despite that, I simply cannot understand why the Romans never managed to properly integrate the Goths into the Empire as they did with some tribes in the past, ie defeat them decisively militarily (if necessary) and disperse them in the Empire.
Even if we want to believe that the Romans didn't want to eliminate the Goths outright, as they required their manpower etc, I struggle to believe that the Romans WANTED the Goths, and that is the important part, to exist as an independent, cohesive military force under one or a few leaders within Roman territory. All evidence points towards Rome tolerating that due to lack of force, instead preferring eg to assimilate and disperse the Goths. There's lots of evidence for this and for the Roman weakness:
Adrianople was a big defeat. But why did the Romans not manage to defeat the Goths on the Balkans decisively for some 10-20 years afterwards? They only lost some 20.000 or so men. Supposedly (N.D.) the ERE had some 200.000 or so men. Even if we assume over half of these were guarding the East, there should've been sufficient troops, even if only 30.000 men,to defeat the Goths, especially over 10+ years. Yet suspiciously, there weren't. Why?
Stilicho, the supreme commander of the West in control of especially all troops in Italy, the strongest remaining force of the WRE, could never defeat Alaric outright. Why? This was pre 410, supposedly the WRE army should still be quite strong at this point.
Part 1:
Now one of the simplest explanation is that there was a lack of eager recruits. It is significant that there no longer seems to have been machinery for the mass call-up of a national army. The provision of recruits had become a tax on landowners, who were divided into consortia with the obligation to furnish a certain number of recruits between them. These people did not in fact organize a local conscription, but operated a kind of press-gang system, combining incentive payments with coercion, to induce a few individuals to enrol. Of the new recruits, some were unsuitable, and more extremely reluctant to serve. Even so, the duty of providing recruits was extremely unpopular with landowners, who preferred to commute the obligation into a money payment. Money thus collected was used to hire barbarians. It is by no means inevitable that such a system of recruiting would produce bad soldiers (after all, crews raised by the press-gang won the battle of Trafalgar), but it must have been extremely difficult to raise large numbers of troops in this way.
One might think that the danger of the Empire would have produced numerous volunteers. In fact the danger was not realized widely. There was, furthermore, very little active imperial patriotism. If men worried about invaders they thought of defending their village, and not of enrolling for military operations that would take them hundreds of miles away. But without large scale spontaneous enrolment there was really no way of getting hold of the mass of the peasant population, even if manpower was available. In the 'good old days' of the Hannibalic War, when the Romans managed to call up an extraordinarily large proportion of the age groups liable to conscription, the efforts of the Roman magistrates must have been assisted by readiness and even eagerness to serve among the citizens. Citizenship meant something, and the Romans-and their allies were militarized to an extraordinary degree.
A relevant phenomenon was reluctance of landowners to see their tenants enrolled in the army. We have contemporary evidence for the successful efforts of the senators of Rome to prevent the conscription of their tenants at a time when Gildo, the rebellious commander in North Africa, was cutting off the food supply of Rome. The ability of landowners to interfere with the government's effort to call up the peasantry was certainly much greater than under the Early Empire because a much larger proportion of land, particularly in the West, was now part of large estates. Moreover the weakening of the cities meant that even the independent country population attached itself for protection to the patronage of landed magnates. It must have been very difficult indeed to carry out recruiting on a large scale in the face of obstruction by both peasantry and landowners. It is perhaps not surprising that the imperial government gave up the struggle and preferred the easier policy of enrolling barbarians.
Military service was highly unpopular, especially as it no longer served as a pathway to gain citizenship. Even sections of the Roman Empire that were still highly militarised, such as Roman Gaul, were only eager to protect their own borders, not that of the whole empire. Ammianus Marcellinus, writing in the 4th century, praises the bravery of the Gauls:
“The men of every age are equally inclined to war, and the old man and the man in the prime of life answer with equal zeal the call to arms, their bodies being hardened by their cold weather and by constant exercise so that they are all inclined to despise dangers and terrors. Nor has any one of this nation ever mutilated his thumb from fear of the toils of war, as men have done in Italy, whom in their district are called Murci.”
Despite this, the Romano-Gallic army rose up in rebellion when asked by Constantius II to protect the borders of the eastern Roman Empire against the Persians. Emperor Julian was declared emperor after promising the Romano-Gallic army that he would not force them to serve beyond the Alps (although he later took back his promise). Therefore, there was a general lack of imperial patriotism. As previously stated, if men worried about invaders they thought of defending their village, and not of enrolling for military operations that would take them hundreds of miles away.