Gao Xianzhi
In 755, An Lushan, after Yang Guozhong repeatedly had provoked him, rebelled, and the generals Gao Xianzhi and Feng Changqing, after failing to defeat An, were executed. Emperor Xuanzong put Geshu in charge of 200,000 soldiers and had him take up command at Tong Pass, succeeding Gao Xianzhi. In 756, Emperor Xuanzong also gave Geshu the honorary titles of "Zuo Pushe" (), one of the heads of the executive bureau of government (尚書省, "Shangshu Sheng") and chancellor "de facto" (同中書門下平章事, "Tong Zhongshu Menxia Pingzhangshi"). Once Geshu got to Tong Pass, his subordinates suggested that he make a surprise attack on Chang'an and kill Yang Guozhong, seeing Yang Guozhong as the cause of An's rebellion—which Geshu rejected, stating, "If that happens, it is Geshu Han who is a rebel, not An Lushan." However, the news was leaked to Yang Guozhong, who, in apprehension, gave his associate Du Qianyun () a separate command, nominally under Geshu. Geshu, now suspicious of Yang Guozhong's intentions, took an opportunity where he summoned Du to Tong Pass to discuss military affairs to execute Du, increasing the tension with Yang Guozhong. Meanwhile, Geshu was still inimical to An Sishun. Geshu forged a letter from An Lushan to An Sishun, and then had the messenger captured at a pass. He presented the letter to Emperor Xuanzong, along with a petition accusing An Sishun of seven crimes. As a result, An Sishun and An Yuanzhen were executed, and their families were exiled to the Lingnan region, despite Yang Guozhong's attempt to intercede on An Sishun's behalf.