Mongolian Plateau
The Dzungar Khanate was ruled by the Oirats, who had a longtime rivalry with the Khalkha Mongols, who by the later 17th century became the remnants of the Northern Yuan dynasty. After the death of Galdan Boshugtu Khan's brother at the hands of the Northern Yuan dynasty, he attacked them, decisively defeated them, and occupied the Mongolian Plateau. The remnants of the Northern Yuan dynasty submitted to the Qing dynasty in the hope of being restored as a client state. Motivated by the opportunity to gain control over the Mongolian Plateau and by the threat posed to them by a strong, unified Mongol state such as the Oirats threatened to form, the Qing sent their army north to subdue the Dzungars.