The Yenisei Kyrgyz, also known as the Khyagas or Khakas, were an ancient Turkic people that dwelled along the upper Yenisei River in the southern portion of the Minusinsk Depression from the 3rd century BCE to the 13th century CE. The heart of their homeland was the forested Tannu-Ola mountain range (known in ancient times as the Lao or Kogmen mountains), in modern-day Tuva, just north of Mongolia. The Sayan mountains were also included in their territory at different times. The Kyrgyz Khaganate existed from 550 to 1219 CE; in 840, it took over the leadership of the Turkic Khaganate from the Uigurs, expanding the state from the Yenisei territories into the Central Asia and Tarim basin. The Yenisei Kyrgyz mass migration to the Jeti-su resulted in the formation of the modern Kyrgyz Republic, land of the modern-day Kyrgyz. However it is believed that the Khakas people and Fuyu Kyrgyz are closer to the ancient Yenisei Kirghiz, who are both Siberian Turkic peoples (Northeastern Turkic), rather than the Kyrgyz people of modern Kyrgyzstan, who are Kipchak Turkic people (Northwestern Turkic).