The situation was transformed by nomadic, non-Germanic Hunnish horsemen from the east who pushed Germanic peoples into the Roman Empire in several waves. First, in 376, Visigoths were admitted by the emperor Valens as foederati (“allies”) to farm and defend the frontier. This procedure was not without precedent and was unusual only in the enormity of the group involved (traditionally estimated at about 80,000). The Romans were unprepared for such a large group, and their failure to accommodate the group and outright hostility toward the Visigoths led to confrontation. Two years later the Visigoths killed Valens, winning a famous victory at Adrianople (now Edirne, Turkey), though by 382 they had been subdued. Yet, as the Huns moved west, Rome’s frontiers came under increasing pressure, and further large incursions (by Germanic as well as other peoples) occurred in 386, 395, 405, and 406. Some of the invaders were defeated, but Germanic Vandals and Suebi established themselves in Spain and later in North Africa, and the Visigoths exploited the disorder to rebel, especially after the election of Alaric as king. Marching to Italy, they demanded better terms, and, when these were not forthcoming, they sacked Rome on August 24, 410. Even though Rome was no longer capital of the empire, the sack was a profound shock for the people of the empire.

The Roman Empire nevertheless remained an important power in Europe, both militarily and economically. Hence Germanic groups on the run from the Huns were anxious to make peace; even the Visigoths accepted a settlement in Gaul in 418. Since Germanic peoples had no sense of either common interests or common identity, they could be played off against one another; thus the Vandals were savaged by the Visigoths between 416 and 418. Until about 450 fear of the Huns meant that the empire could, in moments of crisis, mobilize at least Visigoths, Burgundians (received into Gaul after being defeated by the Huns in 439), and Franks for its defense. Soon after Attila’s death in 453, however, the Hun empire collapsed, and Rome lost this diplomatic weapon. It also suffered a progressive loss of revenue as territories were either occupied or—like Britain—abandoned by the imperial government. The balance thus swung further in the Germanic peoples’ favour, and they eventually declared themselves independent. In the 470s a Visigothic kingdom emerged in southwestern Gaul and later gained control of most of the Iberian Peninsula. Meanwhile, a Burgundian kingdom arose in southeastern Gaul, and Clovis created a Frankish kingdom in the north. The Vandals already controlled North Africa and the Suebi part of Spain, and Gepid and Lombard kingdoms dominated the Danube. A band of Germans, led by Odoacer, deposed the last Roman emperor, Romulus Augustulus, in 476 and set up a kingdom in Italy. Ostrogoths freed by the collapse of the Hun empire struggled for a generation to find a new homeland. Their struggles sometimes brought them into conflict with the Eastern Empire, whose ruler, Zeno, sought to mitigate the situation by elevating the Ostrogothic king, Theodoric, to the office of patrician. When this solution failed, Zeno sent Theodoric against Odoacer. Theodoric ultimately defeated Odoacer and established a successful Ostrogothic kingdom in Italy that lasted from 493 to 555.

These Germanic successor states brought the Roman Empire in western Europe to an end. The empire could have resisted any of them singly, but the Hun invasions had pushed too many Germanic groups across the frontier too quickly. Battles, however, were the exception. More often the empire unwillingly, but peacefully, granted areas for settlement, and, as Rome became increasingly weaker, the local Roman provincial population looked to the newly settled Germanic peoples for protection. This period thus continued the transformation of the Germanic world. Because of the danger from Rome and the Huns, Germanic political units again increased in size. The new Germanic groups also fell under the influence of the Roman populations they came to rule. Literate, educated Romans enabled German kings systematically to raise taxation and expand their legal powers. The successor states to the Roman Empire were thus a fusion of Germanic military power and the administrative know-how of Roman provincial aristocrats. Transformation was complete in these regions when Germanic warrior and Roman provincial elites quickly intermarried, bringing into being a new aristocracy that was to shape medieval Europe.

Within the boundaries of present-day Germany, the Hunnish conquest drove Germanic peoples out of the region to the east of the Elbe and Saale rivers during the early 5th century. This area was subsequently settled by peoples speaking Slavic languages, and present-day eastern Germany remained Slavic for some seven centuries. To the west and south, Germanic peoples such as the eastern Franks, Frisians, Saxons, Thuringians, Alemanni, and Bavarians—all speaking West Germanic dialects—had merged Germanic and borrowed Roman cultural features. It was among these groups that a German language and ethnic identity would gradually develop during the Middle Ages.