The Orkhun Inscriptions are composed of four monuments located at the banks of the Orkhun River in Mongolia. They were first discovered by a Swedish captive officer during the 18th century, but it was Thomsen, a Danish scientist, who was able to de-code the Turkish Runic Alphabet and thus read the inscriptions in the late-19th century.

These inscriptions date back to 730s AD, and were erected just after the deaths of Bilge Khaghan, Kül Tigin and Tonyukhukh. They were written in the Turkish Runic Alphabet, which was also de-coded by both Thomsen and Radloff.

So, who were these rulers and which nation did they belong to? They were the rulers of the II. Türük (also called as Gokturk, Kök Türük and Tu-jüe) Khaghanate, which was founded by Iltirish Khaghan and his Ayguchı (Prime Minister) Tonyukhukh in 681 AD. Bilge Khaghan and Kül Tigin were brothers from the Imperial Family Ashına (A-shih-na in Chinese), and Bilge later became the Khaghan (title equivalent of Emperor), while his brother Kül Tigin (Tigin meant Prince) became the Grand Commander of the Türük armies (for more information, please read my II. Gokturk Empire article).

http://janissary.batcave.net/orkhun.htm