The Qïrghïz as a separate ethnic group were first mentioned under this name and on the territory that they presently occupy at the end of the 15th century. Their previous history and especially their relationship to the Qïrghïz of the Yenisey basin, who formed a powerful nomadic state which destroyed the Uyghur Qaghanate in the 9th century (see map 10), are still a matter of controversy in scholarly literature. Several theories have been offered to explain this relationship, but none of them seems to be definitively proven. The prevailing opinion now is that the Qïrghïz of the TienShan included some nomadic groups that inhabited this region for several centuries, as well as other groups, related to the Yenisey Qïrghïz, who migrated to the south from the Altay region later (the time of this migration is uncertain, but it probably happened during the first expansion of the Oyrats in the 15th century), bringing with them the ethnic name Qïrghïz.
An important factor in the formation of the Qïrghïz of the Tien-Shan was the decline of the Chaghatayid khanate of Moghulistan in the 15th-16th centuries (see maps 26-27), when some Moghul tribes (or parts of them) apparently joined the Qïrghiz, while others joined the Qazaqs. In the process of their formation the Qïrghïz incorporated groups of various origins, some of which may be traced back, according to many scholars, to the time of the Türk Qaghanate, and others may be traced to tribes of Mongol origin (such as the Nayman) or to pre-Mongol tribes of the Dasht-i Qïpchaq (such as the Qangdï, from Qanglï). Whatever their origin, by the 16th century they together formed one distinct entity. Since that time they were concentrated in the Tien-Shan and (especially later) farther south, down to the Pamirs.
In the 17th century the Qïrghïz were pressed by the Junghars and, escaping them, spread out southward, to the Ferghana basin, and eastward, to the oases of Eastern Turkestan; after the destruction of the Junghars some of them returned to their previous homes.

The Qïrghïz tribes were divided into three main groups. Two of them together were called Otuz uul (“Thirty sons”), and had two “wings,” right (ong) and left (sol); the right wing was much more numerous than the left, and it was subdivided into three branches, Tagay, Adigine, and Mungush .The tribes of the Tagay branch occupied the largest section of the Tien-Shan mountain region. It included the largest Qïrghïz tribes, the Bugu, Solto, and Sarï-Bagïsh, who lived in the upper course of the Chu, around Lake Issïq-köl, and farther east, while the tribes belonging to the Adigine and Mungush branches lived to the southwest of the Tagay branch in the foothills of the Ferghana and Alay mountain ranges, the eastern part of the Ferghana basin, and in the Alay valley.
The small tribes of the left wing occupied the valleys and the foothills of the Talas and Chatkal mountains.The third main group of the Qïrghïz was called Ichkilik and occupied the southern parts of the Qïrghïz territory, including the Pamir highlands down to the Wakhan. They apparently migrated to the areas that they currently occupy from Eastern Turkestan in the 16th-17th centuries and later; some of them still extend into Eastern Turkestan.