Answer:
Chinese forces secured the northwestern border against invasions by Mongols and Turks.
Step-by-step explanation:
Qianlong was the 4th emperor of the Qing dynasty ruled China for six-decade reign. Emperor Qianlong carried a range of military attacks that defeated the Turk and Mongol in northeastern China border. He expanded his empire by founding the New Province (Xinjiang) and strengthened authority in the south and east.