Turkic-speaking horse and cattle herders who carried steppe pastoralism farther north than anyone else on earth, settling the Lena's grassy alases after being pushed off the Baikal steppe — the most populous and most state-like of Siberia's indigenous peoples.
Not an ending: Cossacks reached the Lena in the 1620s, founded Yakutsk in 1632, and by 1642 the valley was under tribute after a long siege of a Yakut fortress; resistance recurred for two centuries. The Sakha are now the majority-titular people of the Sakha Republic (Yakutia), the largest subnational territory on earth, and over 90 percent still speak Sakha as a mother tongue.
The classic monograph on the Yakut by a Jesup Expedition ethnographer who spoke the language — clan organization, cattle economy, and the pre-Russian past.
Used for the Lena conquest specifically — the 1620s Cossack advance, Yakutsk 1632, and the Yakut revolts that followed.