In 375, westward-expanding Huns from Central Asia slammed into the Black Sea region Alans and Ostrogoths, routing them in battle with their cavalry-borne assaults. Those not enslaved fled frantically, displacing all in their path. In the next years, the limes erupted. Terrified by the experience of their northeastern neighbor, the Visigothic king Fritigern implored Valens to allow his tribe to migrate into Roman realms and settle south of the Danube. Valens delayed, then acquiesced in 376. Though the agreement was Visigothic disarmament in return for Roman provisions, the arrangement quickly broke down. Rising Roman mistreatment of Visigoths who had already suffered from forced migration, as well as non-arrival of food and some atrocities reflecting Greek distaste for their new neighbors, caused the Visigoths to revolt at the end of 376. By 378, Valens had arrived from Antioch with an army, yet failed to await Gratian's reinforcements and was routed at Adrianopole (modern Edirne) after Ostrogothic cavalry came to their brothers' aid. Valens was killed. Theodosius (379-95) controlled the damage by settling the Visigoths en masse as foederati on the Roman side of the border in Bulgaria—the first time Barbarians had been allowed into the empire as an entire group. After decimation of the Eastern Roman army, the Visigoths were welcome new soldiers. Theodosius began whole-scale Germanization of both Eastern and Western military forces at all levels. Resentment among remaining Roman officers and soldiers caused antagonism in the ranks. Theodosius also coaxed the Ostrogoths back over the border out of Roman lands, as the Huns had receded eastwards.
Theodosius was succeeded in 395 by ineffective emperors in both East and West, who did not entirely honor his agreements with the Visigoths. In that year, the activist Alaric was elected Visigothic king, and decided to migrate further into Europe and Italy in search of food and pasture land. Six years later, a mostly Vandal-Burgundian army led by Rhadagaesius crossed the Danube into the northern Alps. In both cases the impetus was a Hunnic return to Southeastern Europe, pushing all before them. Pandemonium ensued in Roman lands.
In 401, Stilicho, the Frankish-Roman military leader, went to subdue Rhadagaesius, allowing Alaric to bring his tribe into northern Italy and engage in limited pillaging. Stilicho defeated Rhadagaesius' forces, however, incorporating them into his army, which pushed Alaric back across the Italian Alps, where he decided to bide his time. Responding to continuing Hunnic pressure, and seeing the withdrawal of Stilicho's army to deal with the Visigothic incursion, Rhadagaesius returned in 405 and 406. Instead of plundering then withdrawing as in the past, he led a great Barbarian army dominated by Vandals, and including Alans, Suevis, and Burgundians, across the frozen Rhine at Mainz. Fanning out across Gaul, they attacked cities and agricultural areas, forcing the indigenous population into the hills. Neither sparse Roman forces nor Frankish auxiliaries could stop them, and eventually, Vandal led-forces crossed into Iberia, settling within Roman lands.
Alaric, seeing this and determined to secure better settlement for his tribe, was inclined by 408 to follow the Vandals into Gaul. Events intervened when the Western emperor Honorius ordered Stilicho's assassination. The Roman-German imperial army in Italy then split along ethnic lines, with Roman soldiers massacring the families of their erstwhile comrades. Then, the German elements defected en masse to Alaric's Visigoths. By 408, there was no army in Italy, so Alaric was able to enter the region and remain for four years. At first, a barbarian sacking of Rome was staved off by bribing Alaric; he returned in 409, however, wanting to negotiate a real settlement involving reintegration into the Roman army and provisions, but Honorius refused to negotiate and fled for Ravenna. A senate-elected emperor, Attalus, consented to Alaric's demands, but could not provide sufficient foodstuffs because North Africa, the capital's bread-basket, did not recognize him. Thus, in 410, the Visigoths undertook the first sack of Rome, though it was limited in duration and severity. The Goths then moved south to obtain a fleet for transport to North Africa and its food. The fleet was destroyed by a storm, and Alaric died. The Goths returned north with Athaulf as new king.
Requiring reconsideration is the significance of the 378 Visigothic defeat of Roman forces at Adrianopole. Theodosius was able to quickly resolve the situation, and though the Eastern Army was decimated and the Eastern half of the Empire was in most direct danger, it was able to continue for more than 1000 years more. Still, the great importance of the defeat was three-fold: 1) Theodosius' agreement to settle Alaric's people within Roman borders was new, and set a precedent, since it was repeated for all others who appeared to acquiesce to Roman suzerainty in the Visigothic manner. 2) While use of Barbarian slaves in Roman forces and employment of Barbarian auxiliaries directly on the other side of Roman borders had already occurred, from the 370s, the whole sale Germanification of Roman legions began. Though perhaps not understanding entirely what Rome was, Barbarian soldiers were no less loyal than their Latin counterparts (whose loyalties were at times in question); the Germans were perhaps even more versatile and willing combatants. Furthermore, Barbarian military employment was not limited to field forces. Stilicho, the Master of Soldiers until Honorius assassinated him in 408, was himself a Vandal, though it is likely that he saw himself as being as Roman as his predecessors. Ironically, then, Germanics like Stilicho and all who followed him as Master of Soldiers comprised all that was left of Roman military might to limit Germanic encroachment, or channel it away from Imperial interests. 3) After the death of Theodosius in 395, under whom the Empire was briefly united in name under one Emperor, Eastern and Western emperors would have increasingly less interaction. In some cases this mutual turning away was related to the use of Barbarian soldiers; when it was popular in one region, the court in the other area would turn against it. Beyond that, though, the capabilities of the two halves were so constrained by immediate local challenges that the luxury of intervention no longer existed. Of course, that the Visigoths (and later the Huns) elected to go west likely saved emerging Byzantium, whose only policy recourse during the dark years from 380-430 was to attempt to mediate and thus restrict Barbarian access to Mediterranean coastal areas, ocean vessels, and grain supplies.
To the extent that Roman policy failed during this period, due consideration must be given to the role of poor imperial policy and individual emperors' stupidity. Honorius' constant bickering with his Eastern colleague was not helpful, just as the latter's support of counter-claimants in the West could only be debilitating and wasteful of military manpower. Also, Honorius' flight to fortified Ravenna without fending off by force or negotiation the Visigothic sack of Rome has been interpreted as lack of will, cowardice, or stupidity. Interpreting his actions differently by assuming he actually had a policy, it could be said that he had a difference of opinion with Stilicho as well as with the Senate. Stilicho preferred to fight, while the Honorius was ready under duress to respond favorably to Alaric and Athaulf's demands. According to this view, Honorius recognized that force would not carry the day, that acquiescence to Visigothic demands would open the door to their settlement in Italy (as opposed to elsewhere in Roman lands), and that Rome was no longer strategically significant. Perhaps, then, the Visigothic departure from Italy in 412 could be read as Honorius' eventually Pyhrric victory.
Finally, the student must confront the difficult yet central question of the extent and quality of the Barbarization of both Roman state and Roman society beginning in the 370s. First, it is no longer possible to view the process as a sudden, calamitous, or even apocalyptic process. As an example, though struggling with invasions put a tremendous burden on economy and finances, these invasions themselves were not responsible for the Empire's economic woes. Basically, the Roman economy was neither productive, entrepreneurial, nor technologically innovative. Spoils of war and governmental largesse had driven economic growth, which is not the same as development. As conquest slowed, new sources of tribute ceased to materialize, and the price of a large and expanding army was felt ever more. In this context, and with coinage losing value, the drift of elites to rural landowning and the growth of latifundias is understandable, though it damaged urban commerce.
Second, many elements of Roman life had undergone Barbarization prior to the 370s. The increasingly large scale use of Barbarian slaves in all aspects of unfree labor meant that Romans were aware of and assimilating Barbarian ways. Early fifth-century laws forbidding Roman sporting of trousers, vests, and long hair attest to the attraction to Barbarian styles. Of course, the Barbarization of Rome continued much more intensely after the large-scale importation of Germans into Roman cities and the army.
Third, it is possible to posit a Romanization of the Barbarians. Service in Roman Legions as soldiers and officers not only accustomed them to Roman forms, but to a degree instilled in them a Roman identity, or a sense that the Roman way should be the aspired-to goal. Whether in Roman office (usurped or not) or as landowners manipulating foederati agreements, Germans in Roman lands assimilated into the system as much as they could.
What prevented a more thoroughgoing melding of cultures within the umbrella of the Roman imperial edifice? Some of the factors were A) opposition on the part of large segments of Roman traditionalists, both urban and rural; B) the already compromised state of the Roman polity, military, and economy from the 370s; C) constant political and military bickering between emperors, claimants, and the senate, which made policy continuity impossible; D) the sheer difficulties of assimilating such comparatively large numbers of Barbarians, who were not predisposed to immediately grasp or cultivate Roman society; E) Barbarian religious differences; and F) German legal conventions. These last two were perhaps the most lasting inhibitors of cultural coalescence.
It is true that all the Germanic tribes of note (except the Angles, Saxons, and Franks) had converted to Christianity before their entry into Roman lands. Unfortunately for the German integration into a Roman society that was increasingly Christians, the Germans had been converted into the Arian form of the faith. Arius had been a priest in Alexandria Egypt in the 320s. Combining principles of Hellenic philosophy prevalent in this center of ancient learning with the notion of Jesus Christ being the son of God, he concluded that Christ must be less than God, as he was both junior to him and not eternal. Though denounced by the local Bishop and other Church leaders, some agreed with Arius, as his position was philosophical sound in those days' terms. Eventually, the 325 Council of Nicaea (in modern Iznik, Turkey) established as Orthodox creed the divine equality of Jesus and God, yet several clerics did not accept it; in fact, though the council had been presided over and directed by Constantine, in the ensuing fifty years the Eastern Empire would occasionally and temporarily changed its orthodoxy back to Arianism for a while. It was during one of these returns to Arianism that Ulfillias converted the Goths. Still, the West had never accepted Arianism. In the West, the idea that Christ was not quite as divine as God was blasphemous heresy, and an insurmountable barrier to meaningful Roman-German integration was erected.
Lastly, in a state where law was held to be the basis of all interaction, German law was completely foreign to the Roman sense of legal decency. In Rome, with the exception of the single sovereign Emperor, civil and military authority had long been totally separate. The opposite was the case in Germanic custom, in which the ruling assemblies held all sway. Furthermore, when settled in Roman lands as military foederati, the Barbarians were made exempt from Roman civil law. Not only did this constitute an affront to Roman practice, but Germanic law, such as it was, was revolting to Romans. More than assigning responsibility, guilt, or innocence, Germanic law was designed to avoid blood- feuding, which was rampant and debilitating. Thus, by means of wergild, or 'worth-money', Germans sought to circumvent revenge by instituting the recompense of financial sums for various bodily injuries or homicides. Further, testings, in which an accused person's was subjected to ordeals such as drowning or burning, were used to establish guilt, based on a pagan past. Also, and of real insult to Romans who believed in the ideal of equality, all the different wergild scales and legal systems of the various tribes were based on the principle that law, or nationality for that matter, was not territorial, but personal, and dependent on social status and ethnicity. At this point, with several Barbarian tribes settled from Iberia to the Rhine, Roman law, Res Publica, long the pillar of Roman society, ceased to have any real meaning.