Military advancement on the northeastern frontier
The Tang histories place An Lushan's early career around Liucheng in Yingzhou and the northeastern borderlands. They describe his command of several languages and work as an intermediary in frontier trade. Service under Zhang Shougui, including reconnaissance and fighting alongside Shi Siming, brought promotion into positions controlling military resources.
He became military commissioner of Pinglu in 742, added Fanyang in 744 and acquired Hedong in 751. Concentration of several commands supplied troops, horses and provisions on a substantial scale. Officers, administrative staff and frontier communities formed different parts of the organization supporting his authority.
Court connections and the rebellion of 755
Visits to court and Emperor Xuanzong's favor strengthened An Lushan's position. The histories describe his dealings with Li Linfu and Yang Guozhong and growing suspicion of his military power. Their explanations reflect retrospective judgments about the crisis; appointments, deployments and exchanges of envoys also reveal concrete connections between court and frontier.
In the winter of 755 he raised his army at Fanyang, claiming to act against Yang Guozhong, and advanced into Henan. His forces captured Luoyang. In 756 he proclaimed himself emperor of Yan, adopted the reign title Shengwu and appointed officials. The insurgents subsequently broke through Tong Pass and occupied Chang'an as Xuanzong left for Sichuan.
An internal coup and the continuation of war
An Lushan was killed in an internal coup in 757. The histories identify his son An Qingxu, Yan Zhuang and the attendant Li Zhu'er among those involved, linking the plot to succession and fear within the leadership. An Qingxu succeeded him and retained forces and occupied territory.
An Qingxu was later killed by Shi Siming, and the Yan military organization underwent further changes of leadership. Tang forces, with other armies and Uyghur assistance, recovered the capitals, but the war continued until 763. An Lushan's career explains the movement from frontier command to rebellion; the larger conflict also encompasses warfare and social disruption after his death.