Geshu Han
Originally, An Lushan's forces were blocked from the main imperial (or "Western") capital at Chang'an (modern Xi'an), by loyal troops placed in nearly impregnable defensive positions in the intervening high mountain passes of Tongguan. Unfortunately for Chang'an, the two generals in charge of the troops at Tong Pass, Gao Xianzhi and Feng Changqing, were executed due to a court intrigue involving the powerful eunuch Bian Lingcheng. Yang Guozhong, with grossly inept military judgment, then ordered the replacement General Geshu Han, who was in charge of the troops in the passes, together with reinforcement troops, to attack An's army on open ground. On 7 July, the Tang forces were defeated. The road to the capital now lay open.