Chionites had arrived in the mid-4th century with the wave of immigration from Central Asia into Iran in late antiquity. They had been influenced by the Kushan and Bactrian culture, and had become a threat on the northeastern frontiers of the Sassanid Empire.
According to A.S. Shahbazi (article dated 2005):
On the northeastern front, the Chionites (q.v.), a Hunnic people who by the early fourth century had mixed with north Iranian elements in Transoxiana and adopted the Kushan-Bactrian language, threatened Persia..
According to Wolfgang Felix (article dated 1992):
The Chionites were a tribe of probable Iranian origin that was prominent in Bactria and Transoxania in late antiquity.
According to Richard Nelson Frye (book dated 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 tribesman from the east and north, although most probably the bulk of the people in the confederation of Chionites and then Hephtalites spoke an Iranian language and 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.
According to Carlile Aylmer Macartney (article dated 1944):
We must consider briefly a third nation playing a role in our sources: the Kermichiones. Who were these people? They cannot have been the Turks-Toue-Kioue, since their embassy reached Constantinople while the Avars were still negotiating with Rome for settlement inside the frontier-probably, therefore, as early as A.D. 558, whereas the true Turks appeared there first in 568; further, their ruler's name was `Aσκήλτ or Scultor, while the Khagan of the Turks at that time was Silzabul, Dizabul, or Istämi. Neither can they have been the Juan Juan, as Marquart suggests; nor the Epthalites, who were well known to the Byzantines and would not have been described in this way. Moreover, the Epthalites were known as White Huns, and Mr. Bailey has pointed out that the word Karmir xyon, meaning Red Chyon, occurs in a Pahlavi text in juxtaposition with SpEt xyon, White Chyon. The name Chyon, originally that of some other race, was "transferred later to the Huns owing to the similarity of sound". The nation can hardly be other than that which appears in the fourth century, under the name of Chionits, in the steppes on the north-west frontier of Persia. These Chionites were probably a branch of the Huns, the other branch of which afterwards appeared in Europe, the latter appear to have attacked and conquered by the Alans, then living between Urals and the Volga about A.D.360, while the first mention of the Chionites is dated A.D.356. In the fifth century the name is replaced by that of the Kushan or of the Kidarite Huns, who are clearly identical with the Kushan.
According to Sir Harold Walter Bailey (article dated 1932):
Xyon. This name is familiar in Pahlavi and Avestan texts. It would appear to be a name of 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. In the present passage (a passage from the Pahlavi book of Bahman Yasht) three divisions of this people seem to be recognized, the Xyon with the Turks, the Karmir (Red) Xyon, and the White Xyon.
In the earliest periods, Xiōng (匈) were more of a concern to the Chinese than to the Persians. They dominated the smaller Donghu nations beyond Tianshan in the East Asian steppes who were known as the Xiong (匈)'s Serfs until the Xiōng (匈)'s hold over them was broken by the Chinese by the end of the Sino-Xiongnu War. Chionitae campaigns are better documented in connection to a number of events of the political history of Central Asia particularly during the second half of the 4th century AD until the mid 5th century AD. Their most famous rulers were called the Kidarites. At the end of the 4th century AD, a new wave of Hunnic tribes (Alchoni) invaded Bactria, pushing the Kidarites into Gandhara.
Although the power of the Alchon in Bactria was shattered in the 560's by a combination of Sassanid and proto-Turkic forces, the last Hephthal king Narana/Narendra managed to maintain some kind of rule between 570 and 600 AD over the 'nspk' or 'napki' or 'nezak' tribes that remained after most of the Alchon had fled to the west.