In spring 657, Emperor Gaozong again launched a campaign against Western Turks, this time with Su Dingfang in command, assisted by the generals
Ren Yaxiang and Xiao Siye (), along with troops from Tang's ally
Huige and also Western Turks chiefs
Ashina Mishe () and
Ashina Buzhen (), who took a southern route relative to Su's main forces, which took a northern route. Su first attacked Chumukun, defeating it. Su soon engaged Ashina Helu's army of nearly 100,000 men, with less than 20,000 men himself. Ashina Helu, believing that he could crush Su's smaller army easily, ordered a charge, but could not break through Su's infantry formation, armed with long spears. Su then counterattacked with cavalry, defeating Ashina Helu and killing and capturing several tens of thousands of men. The next day, as Su continued to advance, the commanders of the five western tribes of Western Turks (which consisted of 10 tribes), including the general Huluwu (), surrendered, and Ashina Helu fled along with his general Qulü (). The commanders of the five eastern tribes surrendered to Ashina Buzhen. As Su continued to advance to chase after Ashina Helu, he encountered snow storms, and when his subordinate generals suggested that they halt until the weather got better, Su pointed out that Ashina Helu would be surprised that they were continuing to chase him through the snow and could thus caught be surprised. He joined forces with Ashina Mishe and Ashina Buzhen, and made a surprise attack on the regrouping Ashina Helu, again defeating him and capturing or killing some tens of thousands of men. Ashina Helu fled to Shi (石國, modern
Tashkent), a vassal of Western Turks, but Shi, not willing to risk being attacked by Tang forces as well, captured and turned Ashina Helu over to Tang forces. The independent Western Turkic Khaganate was no more (although from time to time Tang and
Tibet would create members of the royal family khans to try to pacify the region—as it immediately tried to do, creating Ashina Mishe Xingxiwang Khan (興昔亡可汗, literally "the khan who would raise what had been destroyed) and Ashina Mishe Jiwangjue Khan (繼往絕可汗, literally, "the khan who will continue what had been ended"), although Ashina Mishe would eventually be falsely accused of treason by Ashina Buzhen and killed, and after Ashina Buzhen's own death soon thereafter, the scheme fell apart). When Su presented the captured Ashina Helu to Emperor Gaozong, Emperor Gaozong spared Ashina Helu and promoted Su to be a major general. He also created Su the Duke of Xing, while creating Su's son Su Qingjie () the Duke of Wuyi. ==Campaign against Sijie==