[2] The term refers to the important role played by the migration, invasion, and settlement of various tribes, notably the Burgundians, Vandals, Goths, Alemanni, Alans, Huns, early Slavs, Pannonian Avars, Bulgars and Magyars within or into the territories of the Roman Empire and Europe as a whole.

The first migrations of peoples were made by Germanic tribes such as the Goths (including the Visigoths and the Ostrogoths), the Vandals, the Anglo-Saxons, the Lombards, the Suebi, the Frisii, the Jutes, the Burgundians, the Alemanni, the Sciri and the Franks; they were later pushed westward by the Huns, the Avars, the Slavs and the Bulgars.

[8] Later invasions, such as the Vikings, the Normans, the Varangians, the Hungarians, the Arabs, the Turks, and the Mongols also had significant effects (especially in North Africa, the Iberian Peninsula, Anatolia and Central and Eastern Europe).

A later wave of Germanic tribes migrated eastward and southward from Scandinavia, between 600 and 300 BC, to the opposite coast of the Baltic Sea, moving up the Vistula near the Carpathian Mountains.

During Tacitus' era they included lesser-known tribes such as the Tencteri, Cherusci, Hermunduri and Chatti; however, a period of federation and intermarriage resulted in the familiar groups known as the Alemanni, Franks, Saxons, Frisians and Thuringians.

They were followed into Roman territory first by a confederation of Herulian, Rugian, and Scirian warriors under Odoacer, that deposed Romulus Augustulus in 476, and later by the Ostrogoths, led by Theodoric the Great, who settled in Italy.

The Lombards, a Germanic people, settled in Italy with their Herulian, Suebian, Gepid, Thuringian, Bulgar, Sarmatian and Saxon allies in the 6th century.

At the same time, the so-called Moors (consisting of Arabs and Berbers) invaded Europe via Gibraltar (conquering Hispania from the Visigothic Kingdom in 711), before being halted by the Franks at the Battle of Tours in Gaul.

Wolfram observed that the significance of gens as a biological community was shifting, even during the early Middle Ages and that "to complicate matters, we have no way of devising a terminology that is not derived from the concept of nationhood created during the French Revolution".

Scholars, such as German linguist Johann Gottfried Herder, viewed tribes as coherent biological (racial) entities, using the term to refer to discrete ethnic groups.

[26] From the 1960s, a reinterpretation of archaeological and historical evidence prompted scholars, such as Goffart and Todd, to propose new models for explaining the construction of barbarian identity.

[33] Modernists propose the idea of "imagined communities"; the barbarian polities in late antiquity were social constructs rather than unchanging lines of blood kinship.

[35] The Austrian school (led by Reinhard Wenskus) popularized this idea, which influenced medievalists such as Herwig Wolfram, Walter Pohl and Patrick J.

[28] It argues that the stimulus for forming tribal polities was perpetuated by a small nucleus of people, known as the Traditionskern ("kernel of tradition"), who were a military or aristocratic elite.

This core group formed a standard for larger units, gathering adherents by employing amalgamative metaphors such as kinship and aboriginal commonality and claiming that they perpetuated an ancient, divinely-sanctioned lineage.

Historians have postulated several explanations for the appearance of "barbarians" on the Roman frontier: climate change, weather and crops, population pressure, a "primeval urge" to push into the Mediterranean, the construction of the Great Wall of China causing a "domino effect" of tribes being forced westward, leading to the Huns falling upon the Goths who, in turn, pushed other Germanic tribes before them.

[39] In general, French and Italian scholars have tended to view this as a catastrophic event, the destruction of a civilization and the beginning of a "Dark Age" that set Europe back a millennium.

[40] In contrast, German and English historians have tended to see Roman–Barbarian interaction as the replacement of a "tired, effete and decadent Mediterranean civilization" with a "more virile, martial, Nordic one".

To this end, noted linguist Dennis Howard Green wrote, "the first centuries of our era witness not merely a progressive Romanisation of barbarian society, but also an undeniable barbarisation of the Roman world.

The Eastern Roman Empire attempted to maintain control of the Balkan provinces despite a thinly-spread imperial army relying mainly on local militias and an extensive effort to refortify the Danubian limes.

The ambitious fortification efforts collapsed, worsening the impoverished conditions of the local populace and resulting in colonization by Slavic warriors and their families.

In contrast, in the east, Slavic tribes maintained a more "spartan and egalitarian"[51] existence bound to the land "even in times when they took their part in plundering Roman provinces".

[55] Influenced by constructionism, process-driven archaeologists rejected the culture-historical doctrine[55] and marginalized the discussion of ethnicity altogether and focused on the intragroup dynamics that generated such material remains.