Southern Yan
In 409, the Southern Yan emperor Murong Chao began a campaign of attacking and pillaging the Jin northern borders, intending to capture men and women to be trained as musicians. In response, Liu Yu decided to launch a campaign to destroy Southern Yan, over the objections of most imperial officials, but was supported by one of Liu Yu's initial allies in starting the uprising against Huan Xuan, Meng Chang (). While Liu Yu was quickly able to defeat Southern Yan main forces in late 409 and put the Southern Yan capital Guanggu (廣固, in modern Qingzhou, Shandong) under siege, Guanggu did not fall quickly. While Liu Yu was sieging Guanggu, Xu Daofu persuaded a reluctant Lu Xun (who was afraid of a confrontation with Liu Yu) to attack north, reasoning that eventually when Liu Yu was ready, Liu Yu would attack first, and that with Liu Yu sieging Guanggu, they could capture the rest of the empire together.