The Xionites appear to be synonymous with the Huna peoples of classical/medieval India, and possibly also the Huns of European late antiquity. It is unclear whether the Xionites were connected to a people named in Ancient China as the Xunyu (Hünyü 獯鬻; Wade–Giles Hsünyü), Xianyun 猃狁 (Wade–Giles Hsien-yün) and Xiongnu (匈奴 Wade–Giles Hsiung-nu). (While some sources use names such as Hunas, Huns and Xiongnu interchangeably, this remains controversial.)
They were first described by the Roman historian, Ammianus Marcellinus, who was in Bactria during 356-57 CE; he described the Chionitæ as living with the Kushans. Ammianus indicates that the Xionites had previously lived in Transoxiana and, after entering Bactria, became vassals of the Kushans, were influenced culturally by them and had adopted the Bactrian language. They had attacked the Sassanid Empire, but later (led by a chief named Grumbates), served as mercenaries in the Sassanian army.
Within the Xionites, there seem to have been two main subgroups, which were known in the Iranian languages by names such as Karmir Xyon and Spet Xyon. The prefixes karmir ("red") and speta ("white") likely refer to Central Asian traditions in which particular colours symbolised the cardinal points. The Karmir Xyon were known in European sources as the Kermichiones or "Red Huns", and some scholars have identified them with the Kidarites and/or Alchon. The Spet Xyon or "White Huns" appear to have been the known in India by the cognate name Sveta-huna, and are often identified, controversially, with the Hephtalites.
See also: Origin of the Huns
The original culture of the Xionites and their geographical urheimat are uncertain. They appear to have originally followed animist religious beliefs, which mixed later with varieties of Buddhism and Shaivism. It is difficult to determine their ethnic composition.
The theory that the Xionites were a proto-Turkic or para-Turkic people was expressed by Sir Harold Walter Bailey (1932). Bailey wrote that the "Xyon" mentioned in "Pahlavi and Avestan texts... would appear to be... an enemy of the Iranian people in Avestan times, transferred later to the Huns owing to similarity of sound, as Tur was adapted to Turk in Pahlavi". Bailey suggested that "three divisions" of the "Xyon ... seem to be recognized", namely "the Turks, the Karmir (Red) Xyon, and the White Xyon."
Differences between the Xionites, the Huns who invaded Europe in the 4th century, and the Turks were emphasised by Carlile Aylmer Macartney (1944), who suggested that the name "Chyon", originally that of an unrelated people, was "transferred later to the Huns owing to the similarity of sound". The Chyon who appeared in the 4th century, in the steppes on the northeastern frontier of Persia were probably a branch of the Huns that appeared shortly afterwards in Europe. The Huns appear to have attacked and conquered the Alans, then living between the Urals and the Volga about 360 AD, and the first mention of the Chyon was in 356 AD. Macartney also considered that the name Chyon was later "replaced by that of the... Kidarite Huns". (However, he also claimed, erroneously, that "the Kidarites were... identical with the Kushan", when the Kushan Empire had been destroyed by the Xionites and/or Hunas in the mid-4th Century.) Macartney also considered the question of the identity of the Karmir Xyon or Kermichiones, saying that that they could not have been "the true Turks" (the Gokturks, who appear to have entered history on the western steppe, when "their embassy reached Constantinople... in 568". Macartney adds that the Khagan of the Turks at the time was Silzabul, Dizabul or Istämi, but the ruler of the Karmir Xyon was Askílt (Aσκήλτ, often romanised as Scultor). "Neither can they have been the Juan Juan [Rouran]... nor the Epthalites [Hephthalites], who were well known to the Byzantines and would not have been described in this way. Moreover, the Epthalites were [sometimes] known as White Huns, and... Karmir Xyon, meaning Red Chyon, occurs in a Pahlavi text in juxtaposition with Spet Xyon, White Chyon".
At least some Turkic tribes were involved in the formation of the Xionites, despite their later character as an Eastern Iranian people, according to Richard Nelson Frye (1991): "Just as later nomadic empires were confederations of many peoples, we may tentatively propose that the ruling groups of these invaders were, or at least included, Turkic-speaking tribesmen from the east and north, although most probably the bulk of the people in the confederation of Chionites... spoke an Iranian language.... This was the last time in the history of Central Asia that Iranian-speaking nomads played any role; hereafter all nomads would speak Turkic languages".
The proposition that the Xionites probably originated as an Iranian tribe was put forward by Wolfgang Felix in Encyclopedia Iranica (1992).
Xionite tribes reportedly organised themselves into four main hordes: "Black" or northern (beyond the Jaxartes), "Blue" or eastern (in Tianshan), "White" or western (possibly the Hephthalites), around Khiva, and the "Red" or southern (Kidarites and/or Alchon), south of the Oxus. Artefacts found from the area they inhabited dating from their period indicate their totem animal seems to have been the (rein)deer. An inscription on the walls of the royal palace in Persepolis about Darius's empire calls them Hunae.
The Xionites are best documented in southern Central Asia from the late 4th century AD until the mid-5th century AD.
See also: Kidarites
Early confrontations between the Sasanian Empire of Shapur II with the Xionites were described by Ammianus Marcellinus: he reports that in 356 CE, Shapur II was taking his winter quarters on his eastern borders, "repelling the hostilities of the bordering tribes" of the Xionites and the Euseni, a name often amended to Cuseni (meaning the Kushans).
Shapur made a treaty of alliance with the Chionites and the Gelani in 358 CE.
Main article: Alchon
At the end of the 5th century the Alchon invaded North India where they were known as the Huna. In India the Alchon were not distinguished from their immediate Hephthalite predecessors, and both are known as Sveta-Hunas there. Perhaps complimenting this term, Procopius (527-565) wrote that they were white skinned, had an organized kingship, and that their life was not wild/nomadic and they lived in cities.
The Alchon were noted for their distinctive coins, minted in Bactria in the 5th and 6th centuries. The name Khigi, inscribed in Bactrian script on one of the coins, and Narendra on another, have led some scholars[who?] to believe that the Hephthalite kings Khingila and Narana were of the AlChoNo tribe.[vague] They imitated the earlier style of their Hephthalite predecessors, the Kidarite Hun successors to the Kushans. In particular the Alchon style imitates the coins of Kidarite Varhran I (syn. Kushan Varhran IV).
The earliest coins of the Alchon have several distinctive features: 1) the king’s head is presented in an elongated form to reflect the Alchon practice of head binding; 2) The characteristic bull/lunar tamgha of the Alchon is represented on the obverse of the coins.
The Hephthalites, or White Huns, were a nomadic tribe who conquered large parts of the eastern middle-east and may have originally been part of the Xionites.
Main article: Hephthalites
Main article: Nezak
According to Bailey, the Hara Huna of Indian sources are to be identified with the Karmir Xyon of the Avesta. Similarly he identifies the Sveta Huna of Indian sources with the Spet Xyon of the Avesta. While the Hephthalite are not mentioned in Indian sources, they are sometimes also linked to the Spet Xyon (and therefore possibly to the Sveta Huna).
More controversially, the names Karmir Xyon and Spet Xyon are often rendered as "Red Huns" and "White Huns", reflecting speculation that the Xyon were linked to Huns recorded simultaneously in Europe.