李光弼
Later in 757, when Emperor Xuanzong's son Emperor Suzong had taken over as emperor, a joint Tang and Huige army recaptured Chang'an and Luoyang from Yan, then under the rule of An Lushan's son An Qingxu (An Lushan having been assassinated by An Qingxu earlier in the year). An Qingxu fled to Yecheng and put up his defense there. A number of Tang generals, including, in addition to Dong Qin, Guo Ziyi, Lu Jiong (), Li Huan (), Xu Shuji (), Li Siye, Ji Guangchen (), Cui Guangyuan (), Li Guangbi, and Wang Sili (), converged on Yecheng and put it under siege, although Tang forces were unable to capture Yecheng quickly. In spring 759, the Yan general Shi Siming, who had briefly submitted to Emperor Suzong but then turned against Tang again, attacked Tang forces at Yecheng and caused them to collapse and scatter, and then killed An Qingxu, taking over as Yan's emperor. He then attacked south. With Guo blamed for the collapse at Yecheng, Li Guangbi was put in overall command of Tang forces in the region, and he put Xu in charge of defending Bian Prefecture (汴州, in modern Kaifeng, Henan). Dong, along with Tian, Liang Pu () and Liu Congjian (), served under Xu. When Shi arrived at Bian Prefecture and initially defeated Xu, however, Xu surrendered, along with Dong, Tian, Liang, and Liu. Shi had long been impressed by Dong, and he patted Dong's back and stated, "Before, I had only a left hand. Now that I have you, lord, I also have a right hand." When Dong subsequently accompanied Shi in capturing Luoyang and then attacking the key outpost Heyang (河陽, near Luoyang), however, he took the opportunity to flee from Shi's camp and rejoin Li Guangbi, then defending Heyang. Emperor Suzong made Dong the military commander of the Shanxi () and Shence () Armies, and bestowed on him not only the imperial surname of Li, but also a new personal name, Zhongchen ("faithful subject"). He also created Li Zhongchen the Duke of Longxi and awarded him with much treasure. Li Zhongchen and another military commander of Shence Army, Wei Boyu (), subsequently defended Shan Prefecture (陝州, in modern Sanmenxia, Henan) against the attacks by Shi's general Li Guiren () and were able to repel Li Guiren.