A previously unknown Khitan inscription inside a cave located on the slope of Naidag Mountain in Lakh bagh, Dashinchilen Soum, Bulgan Province. The field research team included Dr. L. Erdenebold, Director of the Institute of History and Ethnology of the Mongolian Academy of Sciences; Professor Matsukawa Takashi of Otani University; Professor Muraoka Hitoshi of Ryukoku University; and Professor Emeritus Matsuda Koichi of Osaka International University. The inscription was examined by visiting scholar Professor Takeuchi Yasunori of the Institute of Mongolian Studies, Inner Mongolia University.The inscription is located inside a cave more than 200 meters above ground level on the mountainside. Preliminary investigation identified inscriptions in seven separate sections within the cave. 

Professor Matsukawa initially examined the markings, which appeared at first glance to resemble Chinese characters. However, detailed analysis showed that they were not Chinese script but Khitan writing. Photographs were sent to Professor Takeuchi in Hohhot for interpretation. Although the inscription is heavily weathered and difficult to read, he confirmed that many distinctive characters of the Khitan Large Script could be recognized and stated that the inscription was clearly not written in Chinese characters. Most remarkably, he suggested that the fourth inscription may have been written in the Khitan Small Script.

If confirmed, this would represent an exceptionally rare discovery because no previously known site has yielded both Khitan Large Script and Khitan Small Script inscriptions together in the same location.

Naidag Mountain lies near the ancient route connecting Elsen Tasarkhai and Dashinchilen district along the Badiin River at the eastern foothills of Khognu Mountain. The surrounding region contains numerous archaeological remains, including:

• Khitan-period agricultural settlements,
• Bronze Age burial sites,
• runic inscriptions,
• rock art complexes,
• and the ruins of later monasteries.

Mongolia has yielded several important Khitan inscriptions in the past, including discoveries at Rashaan Khad in Khentii Province, Salbar Khoolui, Erdene Mountain, Dongoin Shiree in Sukhbaatar Province, and the Khitan stele inscription of Buleen Ovoo discovered by the Mongolian–Japanese project in Dornogovi Province in 2010.

However, despite the presence of many Khitan-period fortresses and cities in the Tuul River basin — including Chin Tolgoi Fortress, Kharbukh Fortress, Ulaan Kherem, and Khermen Denj — almost no direct Khitan written sources had previously been found there. For this reason, the newly discovered Naidag Mountain inscription is considered highly significant.

The possible presence of both Khitan Large and Small Scripts together at one site may represent the first known example of its kind, offering major potential for future research into the writing system and history of the Khitan world.