When an ally of the Ü-Tsang ruler threatened destruction of <answer>the Gelugpas</answer> again, the fifth Dalai Lama Lozang Gyatso pleaded for help from the Mongol prince Güshi Khan (1582–1655), leader of the Khoshut (Qoshot) tribe of the Oirat Mongols, who was then on a pilgrimage to Lhasa. Güshi Khan accepted his role as protector, and from 1637–1640 he not only defeated <answer>the Gelugpas</answer>' enemies in the Amdo and Kham regions, but also resettled his entire tribe into Amdo. Sonam Chöpel urged Güshi Khan to assault the Ü-Tsang king's homebase of Shigatse, which Güshi Khan agreed upon, enlisting the aid of Gelug monks and supporters. In 1642, after a year's siege of Shigatse, the Ü-Tsang forces surrendered. Güshi Khan then captured and summarily executed Karma Tenkyong, the ruler of Ü-Tsang, King of Tibet.
Which enemies did Güshi Khan defeat? 
the Gelugpas