Following the destruction of the Han-Zhao dynasty in 329, Sima Xun fled south to the Eastern Jin based in Jiankang, where he grew to hold both military and provincial power.
Liu Yao's general, Linghu Ni (令狐泥) discovered Sima Xun and decided to adopt him as his own son.
There, he declared "I am the great-great-grandson of the Empress's Chamberlain, Xun, the great-grandson of the Champion General and Prince Hui of Jinan, Sui, and the son of the Administrator of Lueyang, Guan."
That year, the Inspector of Liangzhou, Huan Xuan (桓宣)[6] passed away, so Yu Yi appointed Xun to replace him.
At the time of Xun's appointment, Cheng-Han held a portion of Liangzhou, so his control was only limited to Jin's half of the province.
The situation changed in 347, when the general Huan Wen conquered Han and took back the remaining parts of Yizhou and Liangzhou for Jin.
[7] Sima Xun marched through the Luo Valley (駱谷; southwest of present-day Zhouzhi County, Shaanxi) and captured Changcheng.
Faced with this crisis, Shi Bao called off his plans and sent Ma Qiu and Yao Guo (姚国) to repel Sima Xun.
Along the way, in c.November, he captured the city of Wancheng from Zhao and killed their Administrator of Nanyang, Yuan Jing (袁景) before returning to his base in Liangzhou.
[10][a] Back in 347, a Jin general by the name of Xiao Jingwen (蕭敬文) had rebelled in Fucheng and declared himself King of Chengdu, stirring trouble in Baxi (巴西; around present-day Langzhong, Sichuan) and Hanzhong.
In late 352, Huan Wen sent Sima Xun to help Zhou Fu, and the two generals finally managed to kill Xiao Jingwen and put down his rebellion.
Sima Xun harassed Qin through the Ziwu Valley (子午谷; east of present-day Yang County, Shaanxi) while Liang's general, Wang Zhuo captured the city of Chencang .
Huan Wen knew of this and tried to appease Xun by making his son, Sima Kang (司馬康), the Administrator of Hanzhong.
The city was abandoned by Guanqiu Wei (毌丘暐), so Sima Xun swiftly captured it before marching on to Chengdu and besieging the new Inspector of Yizhou, Zhou Chu (周楚) on 14 December.
In the middle of 366, Zhu Xu arrived at Chengdu, where he and Zhou Fu jointly attacked Sima Xun's army.