The Oghuz is a linguistic term designating the Western Turkic or Oghuz languages from the Oghur sub-division of Turkic language family. Oghus also spelled Oğuz, or Ghuzz also refers to a 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 all Turkic peoples since antiquity.
According to many historians, the usage of the word "Oguz" dates back to the advent of the Huns (220 BC). Legend has it that the title "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. Greek sources also used the name Oufi (or Ouvvi) to describe the Huns. Prior to the Gokturk state, there are references to the "Sekiz-Oguz" ("eight-Oguz") and the "Dokuz-Oguz" ("nine-Oguz") state formations ruling
different areas in the vicinity of the Altay mountains.
In the 6th century the "six Oguz tribal union" in the Turkic Orhun inscriptions found in the Orkhon Valley in Mongolia, near Ögii Lake. Before the 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.
The main domain of the Oguz 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 are said to have first 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. Mass migrations of the Oghuz into Western Eurasia occurred from the early part of the 9th Century 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 to most of them to converted to Islam and renounced their Tengriism belief system.
Mass migrations of the Oghuz into Western Eurasia occurred from the early part of the 9th Century 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 to most of them to converted to Islam and renounced their Tengriism belief system.
In the mid 9th century, the Oguzes drove the Bechens from the Emba and Ural River region toward the west. By the 10th century, they inhabited the steppe of the rivers Sari-su, Turgai, and Emba to the north of Lake Balkhash of modern-day Kazakhstan. 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 the mass 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.
Also 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.
"The term 'Oghuz' was gradually supplanted among the Turks themselves by the term Türkmen or Turcoman, from the mid 900's on, a process which was completed by the beginning of the 1200s." The Ottoman dynasty, who gradually took over Anatolia after the fall of the Seljuks, toward the end of the 13th century, led an army that was also predominantly Oghuz.
Linguistically, the Oghuz are listed together with the old Kimaks of the middle Yenisei of the Ob, the old Kipchaks who later emigrated to southern Russia, and the modern Kirghiz in one particular Turkic group, distinguished from the rest by the mutation of the initial y sound to j (dj). Today this language is spoken by the Azerbaijanis of the Republic of Azerbaijan and the South Azerbaijan region of Iran, Turks of Turkey and Cyprus, Turkmens of Turkmenistan and northeastern Iran, Qashqay and Khurasani Turks of Iran, Balkan Turks of Greece, Bulgaria and the former Yugoslavia as well as Gauguz (Gokoguz) Turks of Moldova.
Source: Source: https://en.wikipedia.org/wiki/Oghuz_Turks