Kyrgyz in the Mongolian Period
Usy, Han-Hena, and Yilanzhou
In the "Yuan-Shi," in relation to the land of the Kyrgyz, three regions are also mentioned: Usy, Han-Hena, and Yilanzhou. The region of Usy was located "to the east of the Kyrgyz and to the north of the Kyan River (Kem, Yenisei) and received its name from another river; it likely refers to the Us River. Even further east was the region of Han-Hena, where the Kem River flowed and from where two mountain passes led out; skis were used here in winter. Of the region of Yilanzhou, it is only mentioned that it was named after a large snake (in Turkish — yilán or ilan — "snake"). The exact location of this country is not specified further."
Perhaps, during this period, we see approximately the same picture of the settlement of Kyrgyz tribes and the sphere of their influence as in the Tang era, before the Kyrgyz's great power. However, during the Mongol period, the information from historical sources about the Kyrgyz, their settlement, and location is more objective, thus the western part of the land of the Kyrgyz is defined and observed better than based on the historical sources from the Tang era, the nature of which depended on a number of reasons and circumstances.
In the "Bei-shi-ji" (13th century), the Kyrgyz are mentioned in the area of the Ili River. It is likely that this information from the "Bei-shi-ji" referred to the first half of the 12th century when the "Central Asian" Kyrgyz could have inhabited these areas.
It is possible that after the Ghurkhan of the Kara-Khitan "...sent an army to the borders of the Kyrgyz to take revenge for the troubles caused by them, and took Beshbalyk," the "Central Asian" Kyrgyz moved or were pushed north, closer to the Irtysh and Altai. It is possible that after this they migrated to the areas of the Mountain Altai and the Irtysh region, settling to the west of their "Eastern" tribesmen.
Rashid ad-Din reports that "before the era of Chinggis Khan, the rulers among the Naimans were Narkysh-Tayan and Eniyat-Khan. When they defeated the Kyrgyz tribe, Eniyat-Khan did not appear before his elder brother, Narkysh-Tayan, and did not present him with gifts." It is not excluded that the reason for the departure of the "Central Asian" Kyrgyz to Altai could have been clashes with the Naimans (the strongest people of Western Mongolia), particularly the aforementioned defeat by Narkysh-Tayan and Eniyat-Khan, as a result of which the Kyrgyz might have left the lands they occupied. It should be noted that Rashid ad-Din generally refers to the Kyrgyz as "the Kyrgyz Tribe." Therefore, the aforementioned Kyrgyz tribe that was defeated by Narkysh-Tayan and Eniyat-Khan could also refer to the country of the Kyrgyz or part of it.