 In 765, when Emperor Daizong entered into a peace treaty with Tufan, he had Du and fellow chancellor Yuan Zai sign the treaty with the Tufan emissary.In 766, after Xichuan Circuit (西川, headquartered in modern Chengdu) was thrown into a state of civil war after the military governor Guo Ying'ai () was killed by the military officer Cui Gan and several other military officers — Bo Maolin (), Yang Zilin (), and Li Changkui () — rose to resist Cui, Emperor Daizong made Du the military governor of Xichuan as well as the deputy supreme commander of the region, to try to calm the circuit.On the way, though, Du heard that the military governor of Shannan West Circuit (山南西道, headquartered in modern Hanzhong, Shaanxi), Zhang Xiancheng (), had been defeated by Cui, and was afraid to advance.