Güshi Khan
The Oirats converted to Tibetan Buddhism around 1615, and it was not long before they became involved in the conflict between the Gelug and Karma Kagyu schools. At the request of the Gelug school, in 1637, Güshi Khan, the leader of the Khoshuts in Koko Nor, defeated Choghtu Khong Tayiji, the Khalkha prince who supported the Karma Kagyu school, and conquered Amdo (present-day Qinghai). The unification of Tibet followed in the early 1640s, with Güshi Khan proclaimed Khan of Tibet by the 5th Dalai Lama and the establishment of the Khoshut Khanate. The title "Dalai Lama" itself was bestowed upon the third lama of the Gelug tulku lineage by Altan Khan (not to be confused with the Altan Khans of the Khalkha), and means, in Mongolian, "Ocean of Wisdom".