가후
In 198, the warlord Cao Cao attacked Zhang Xiu again despite having suffered an earlier defeat at the Battle of Wancheng in 197. However, he pulled back his forces after learning that Tian Feng, an adviser to his rival, Yuan Shao, had urged Yuan Shao to attack Xu (許; present-day Xuchang, Henan) while he was away at war with Zhang Xiu. Zhang Xiu wanted to seize the opportunity to launch a counterattack, but Jia Xu warned him not to and predicted that he would be lose the battle. Zhang Xiu ignored him and led his troops to pursue Cao Cao's retreating forces. The result was just like what Jia Xu predicted. When Zhang Xiu came back after his defeat, Jia Xu told him to attack again and predicted that he would win this time. Zhang Xiu said: "I didn't listen to you earlier, which resulted in my defeat. Now that I have lost, why should I attack again?" Jia Xu replied: "Changes have taken place. You'll win if you swiftly attack now." Zhang Xiu heeded Jia Xu's advice and attacked Cao Cao again. He won the battle this time.