In fall 623, the Tang general Fu Gongshi, who had served as the deputy of the powerful general Li Fuwei the Prince of Wu as the military governor of the lower Yangtze region, rebelled against Tang rule while Li Fuwei was at Chang'an, declaring himself the Emperor of Song. Emperor Gaozu commissioned Li Xiaogong to attack Fu, again making Li Jing Li Xiaogong's assistant, and also sending other generals Huang Junhan (黃君漢) and Li Shiji to attack Fu from other fronts. Li Xiaogong and Li Jing sailed down the Yangtze, attacking and defeating the Song generals at multiple battles. Fu ordered his generals Feng Huiliang (馮慧亮) and Chen Dangshi (陳當世) to take up position at Mount Bowang (博望山, in modern Ma'anshan, Anhui, preparing for the assault, instructing Feng and Chen not to engage Li Xiaogong, but to wear him down. However, Li Xiaogong, under Li Jing's suggestion, cut off their supply route, and when Feng and Chen's food supplies ran low, they challenged Li Xiaogong. Against suggestions by some officers that he bypass Feng and Chen and attack the Song capital Danyang (丹楊, in modern Nanjing, Jiangsu) directly, Li Xiaogong, again with Li Jing's suggestion, confronted Feng and Chen, initially using the weaker segment of his forces to battle Feng and Chen and, after initial losses, draw Feng and Chen in deeper, and then attacked them, defeating them decisively, with the aid of Li Fuwei's subordinate general Kan Leng (闞稜). After the victory, Li Xiaogong and Li Jing attacked Danyang. Fu, in fear, abandoned Danyang and fled east, but was captured by the local men and delivered to Danyang. Emperor Gaozu, praising Li Jing, made the comment: "Li Jing is the fatal illness for Xiao and Fu. How could even Han Xin, Bai Qi, Wei Qing, or Huo Qubing exceed him?" Subsequently, Li Xiaogong was put in charge of the region, and Li Jing served as his assistant. it was said that Li Jing contributed much in pacifying the region after the region had seen much bloodshed for years.