Orkhon inscriptions in the context of "Iron Gate (Central Asia)"

Proto-Turkic is the linguistic reconstruction of the common ancestor of the Turkic languages that was spoken by the Proto-Turks before their divergence into the various Turkic peoples. Proto-Turkic separated into Oghur (western) and Common Turkic (eastern) branches. Candidates for the Proto-Turkic homeland range from western Central Asia to Manchuria, with most scholars agreeing that their migrations started from the eastern part of the Central Asian steppe, while one author has postulated that Proto-Turkic originated 2,500 years ago in East Asia.

The oldest records of a Turkic language, the Old Turkic Orkhon inscriptions of the 7th century Göktürk khaganate, already show characteristics of Eastern Common Turkic. For a long time, the reconstruction of Proto-Turkic relied on comparisons of Old Turkic with early sources of the Western Common Turkic branches, such as Oghuz and Kypchak, as well as the Western Oghur proper (Bulgar, Chuvash, Khazar). Because early attestation of these non-easternmost languages is much sparser, reconstruction of Proto-Turkic still rests fundamentally on the easternmost Old Turkic of the Göktürks, however it now also includes a more comprehensive analysis of all written and spoken forms of the language.

The Old Turkic script (also known variously as Göktürk script, Orkhon script, Orkhon-Yenisey script, Turkic runes) was the alphabet used by the Göktürks and other early Turkic khanates from the 8th to 10th centuries to record the Old Turkic language.

The script is named after the Orkhon Valley in Mongolia, where early 8th-century inscriptions were discovered in an 1889 expedition by Nikolai Yadrintsev. These Orkhon inscriptions were published by Vasily Radlov and deciphered by the Danish philologist Vilhelm Thomsen in 1893.

The Ongin inscription was discovered in 1891 in Mongolia near the Ongi River, 160 km south of the Orkhon inscriptions and 402 km south-west of the Tonyukuk inscriptions. It was erected in honor of El Etmish Yabgu and written in Yenisey script. Line 12 makes it clear that the author of the inscription erected a memorial to his father. According to Gerard Clauson, it must have been erected between 716 and 735, during the reign of Bilge Qaghan. According to Ercilasun it was erected in 719 or 720.

Orkhon Turkic (also Göktürk) is the earliest version of Old Turkic, known as the oldest Turkic literary language, preceding Old Uyghur. It is the language in which the Orkhon and Yenisei inscriptions are written.

The Tonyukuk inscriptions (Chinese: 暾欲谷碑), also called the Bain Tsokto inscriptions are Turkic inscriptions of the 8th century located in Nalaikh, Ulaanbaatar, Mongolia. They are one of the oldest written attestations of the Turkic language family, predating the Orkhon inscriptions (Khöshöö Tsaidam monuments) by several years.

Vilhelm Ludwig Peter Thomsen (25 January 1842 – 12 May 1927) was a Danish linguist and Turkologist. He successfully deciphered the Turkic Orkhon inscriptions which were discovered during the expedition of Nikolai Yadrintsev in 1889.