Zhang Song
Liu Bei led thousands of his troops into Yi Province and met Liu Zhang at Fu County (涪縣; present-day Mianyang, Sichuan). He also met Zhang Song and Fa Zheng, who willingly provided him with crucial information about Yi Province such as geography, supplies and deployment of military forces. Zhang Song even drew a map of Yi Province and gave it to Liu Bei. As time passed, Zhang Song conceived the idea of betraying Liu Zhang and helping Liu Bei seize control of Yi Province from Liu Zhang, so he contacted Fa Zheng, who agreed to join him.