The Oghuz (a linguistic term designating the Western Turkic or Oghuz languages from the Oghur sub-division of Turkic language family). Also spelled Oğuz, or Ghuzz confederation of Turkic peoples whose homeland, until at least the 11th century AD, was the steppes of central Asia known as Turkistan or Turan, which has been the domain of Turkic peoples since antiquity.
According to many historians, the usage of the word "Oguz" is dated back to the advent of the Huns (220 BC). The title of "Oguz Khan" was given to Mete, the founder of the Hun empire, which is often considered the first Turkic political entity in Central Asia. Also in the 2nd century BC, a Turkic tribe called "O-kut" who were described as Huns (referred to as Hsiung-Nu or "colored-eyed people" in Chinese sources) were mentioned in the area of Tarbogatain, in present-day southern Kazakhstan. It must be noted that the Greek sources used the name Oufi (or Ouvvi) to describe the Oguz Turks, a name they had also used to describe the Huns centuries earlier.
A number of tribal groupings bearing the name Oguz, often with a numeral representing the number of united tribes in the union are noted. Prior to the Gokturk state, there are references to the "Sekiz-Oguz" ("eight-Oguz") and the "Dokuz-Oguz" ("nine-Oguz") state formations ruled different areas in the vicinity of the Altay mountains.
The Oguz community gradually grew larger, uniting more Turkic tribes prior and during the Gokturk establishment. During this period Oguz tribes lived in northeastern areas of the Altay mountains along the Tula River. They were also present as a community near the Barlik river in present-day northern Mongolia. The "six Oguz tribal union" in the Turkic Orhun inscriptions (6th century) pertains to the unification of the six Turkic tribes which became known as the Oğuz. Found in the Orkhon Valley in Mongolia, near Ögii Lake. Before the Orkhon Inscriptions were deciphered by the Danish linguist Vilhelm Thomsen, very little was known about Turkic script. These scripts are the oldest form of a Turkic language to be preserved.
Their main domain in the ensuing centuries was the area of Transoxiana, in western Turkistan. This land became known as the "Oguz steppe" between the Caspian and Aral Seas. Oguz Turks are said to have come there in the period of the caliph Al-Mehdi in the years between 775 and 785 from the Zhetysu now the South-Eastern part of modern Kazakhstan after conflict with the Karluk branch of Uighurs.
By 780, the eastern parts of the Syr Darya were ruled by the Karluk Turks and the western region (Oguz steppe) was ruled by the Oguz Turks.
Mass migrations of the Oghuz into Western Eurasia occurred from the early part of the 9th Century CE onwards, during the period of the Abbasid caliph Al-Ma'mun (813–833). They established trading, religious and cultural contacts with the Abbasid Arab caliphate who ruled to the south. This influence led most of them to converted to Islam and renounced their Tengriism belief system.
It was in this area that one branch of the Oğuz later founded the Seljuk Empire, and it was from here that they spread west into western Asia and eastern Europe during Turkic migrations from the 9th -12th centuries. By the end of the 11th century they controlled an empire stretching from the Amu Darya to the Persian Gulf and from the Indus to the Mediterranean Sea by the end of the 11th century.
Similarly in the 11th century, a Tengriist Oghuz clan—referred to as Uzes or Torks in the Russian chronicles — overthrew Pecheneg supremacy in the Russian steppe. Harried by another Turkic horde, the Kipchaks, these Oghuz penetrated as far as the lower Danube, crossed it and invaded the Balkans, where most they were either crushed or struck down by an outbreak of plague, causing the survivors either to flee or to join the Byzantine imperial forces as mercenaries (1065). Oghuz warriors served in almost all Islamic armies of the Middle East from the 1000s onwards from Byzantium to Spain and Morocco."