It was the arrival of a chief named Amursana at his court that first led Keen Lung to seriously entertain the idea of advancing into Central Asia, and having determined on the Central Asian campaign, Keen Lung's military preparations were commensurate with the importance and magnitude of the undertaking. He collected an army of 150,000 men, including the picked Manchu Banners and the celebrated Solon contingent, each of whom was said to be worth ten other soldiers. The command of this army was given to Panti, the best of the Manchu generals, and Amursana, who accompanied it, received a seal and the honorary title of Great General. But Keen Lung superintended all the operations of the war, and took credit to himself for its successful issue.

The triumph of Amursana, by the aid of the Chinese, did not bring tranquillity to Central Asia. He was not contented with the position to which the friendship of Keen Lung had raised him, and, placing too high an estimate on his own ability and resources, he was inclined to dispute the accepted opinion that all his success was due to the Chinese army. On the termination of the campaign the major portion of that army returned to China, but Panti was left with a select contingent, partly to support Amursana, and partly to secure the restoration of China's authority. Amursana, however, considered that the presence of this force detracted from the dignity of his position. Having risen to the greatness he coveted, Amursana meditated casting aside the prop by which he had risen; but before he took an irretraceable step he resolved to make use of the Chinese forces for extending his authority south of the Tian Shan range into Kashgaria. With some hesitation Panti lent him 500 Chinese soldiers, and with their aid the Eleuth prince captured the cities of Kashgar and Yarkand, and set up a chief named Barhanuddin Khoja as his nominee. This success confirmed Amursana in his good opinion of himself and his resources, and when Keen Lung, who had grown mistrustful of his good faith, summoned him to Pekin, he resolved to throw off the mask and his allegiance to China. At this supreme moment of his fate not the least thought of gratitude to the Chinese emperor, who had made him what he was, seems to have entered his mind. He determined not merely to disregard the summons to Pekin and to proclaim his independence, but also to show the extent of his hostility by adding to his defiance an act of treachery. Before he fully revealed his plans he surprised the Chinese garrison and massacred it to the last man; the valiant Panti, who had gained his victories for him, being executed by the public executioner.

The impression produced by this event was profound, and when Amursana followed up the blow by spreading abroad rumors of the magnitude of his designs they obtained some credence even among the Mongols. Encouraged by this success he sought to rally those tribes to his side by imputing minister intentions to Keen Lung. His emissaries declared that Keen Lung wished to deprive them all of their rank and authority, and that he had summoned Amursana to Pekin only for the purpose of deposing him. To complete the quarrel, Amursana declared himself King of the Eleuths, and absolutely independent of China. But the energy and indignation of Keen Lung soon exposed the hollowness of these designs, and the inadequacy of Amursana's power and capacity to make good his pretensions. Keen Lung collected another army larger than that which had placed him on his throne, to hurl Amursana from the supremacy which had not satisfied him and which he had grossly abused.

The armies of Keen Lung traversed the Gobi Desert and arrived in Central Asia, but the incapacity of his generals prevented the campaigns having those decisive results which he expected. The autocratic Chinese ruler treated his generals who failed like the fickle French Republic. The penalty of failure was a public execution. Keen Lung would accept nothing short of the capture of Amursana as evidence of his victory, and Amursana escaped to the Kirghiz. His celerity or ingenuity cost the lives of four respectable Chinese generals, two of whom were executed at Pekin and two were slain by brigands on their way there to share the same fate. Emboldened by the inability of the Chinese to capture him, Amursana again assembled an army and pursued the retiring Chinese across the desert, where he succeeded in inflicting no inconsiderable loss upon them.