In 659, a vassal of Western Turkic Khaganate (Pin. Tujue) Duman (), a commander of the Izgil () (Pin. Sijie 思結) tribe, rebelled against Tang suzerainty, along with Western Turkic Khaganate subject kingdoms Shule (), Zhujubo (), and Yebantuo () (all in or near modern Kashgar, Xinjiang). The joint forces commanded by Duman quickly defeated the Tang vassal Yutian (于田, in modern Hotan, Xinjiang). In winter 659, Emperor Gaozong sent Su Dingfang against Duman, and once he arrived in the vicinity of Duman's army, he selected 10,000 infantry soldiers and 3,000 cavalry soldiers and made a surprise attack on Duman. When he arrived at Duman's headquarters, Duman was surprised, and after Su initially defeated Duman, Duman was forced to withdraw within the city. Su put the city under siege, and Duman surrendered. In spring 660, Su took Duman back to the eastern capital Luoyang, where Emperor Gaozong was at the time, to present Duman to him. Some officials requested that Duman be executed, but Su made a plea on Duman's behalf that he had promised Duman life before Duman surrendered, and Emperor Gaozong stated that while under the law Duman should die, he would honor Su's promise, and so he spared Duman. The "Old Tibetan Annals", a document in Classical Tibetan that was discovered at Dunhuang in the early 20th century, mentions another battle that Su Dingfang fought against the Tibetans in 659: "Da Rgyal Mang Po Rjes (Chinese: Dayan Mangbuzhi) fought a battle with Su Dingfang of the Tang at the Dongdai 東岱 (a Tibetan regional administrative unit) of Wuhai 烏海 (southwest of Lake Qinghai). Da Rgyal was killed and his army of 80,000 men was defeated by 1,000 Tang troops." Unfortunately, this battle is not mentioned in any other Tang or Tibetan sources, and it remains a mystery whether (not to mention where and how) Su Dingfang actually defeated a Tibetan army that was 80 times larger than his own. Su Dingfang did not remain inactive. Also in spring 660, Tang's ally on the Korean Peninsula, Silla, sought aid from Tang due to attacks from Baekje.