Yuan Shang
In 203, when Yuan Shang attacked Yuan Tan at Pingyuan County, Guo Tu advised Yuan Tan to make peace with Cao Cao and ally with Cao Cao to counter Yuan Shang. After Yuan Tan reluctantly agreed, Guo Tu nominated Xin Ping's brother Xin Pi to serve as Yuan Tan's representative to meet Cao Cao. Xin Pi succeeded in his mission and managed to convince Cao Cao to help Yuan Tan. Cao Cao then led his forces to Liyang (黎陽; present-day Xun County, Henan).