Records of the Three Kingdoms
Fa Zheng, courtesy name Xiaozhi, was from Mei in Youfufeng. He was frustrated in Yi Province and, with Zhang Song, planned to invite Liu Bei in. When Liu Bei besieged Chengdu, Fa Zheng was both envoy and man inside Liu Zhang’s surrender. After the conquest he was governor of Shu commandery and a general, managing the capital region outside and serving as chief planner inside.
In the Hanzhong war he pointed to an opening in Xiahou Yuan’s position. Huang Zhong killed Xiahou Yuan; Fa Zheng was on the side of the decision. In 220 he died before Liu Bei, at forty-five. After the failure at Yiling, Zhuge Liang said that if Fa Zheng had been alive he would have restrained the lord from marching east, and that even if the march had happened it would not have ended in ruin.
Romance of the Three Kingdoms
In the novel his scenes are quieter than Pang Tong’s. During the taking of Shu he and Pang Tong both urge Liu Bei to turn on Liu Zhang. At Dingjun Mountain he reads the ground and sends Huang Zhong out.
After his death the book uses Zhuge Liang’s regret to say that the eastern campaign lacked a man who dared to stop it.
Reference: Wikipedia · Fa Zheng