Cao Cao had twenty five sons. Cao Pi, Cao Zhang and Cao Zhi were born of the same mother, Bian Hou the Queen. Almost every Chinese know the story about Cao Pi trying to kill Cao Zhi by forcing him to make a poem in (the time it took to make) seven strides.

However, not too many people know the story about Cao Pi killing Cao Zhang during a Weiqi game. Cao Zhang was a great rider and archer. He had great strength and like his father, was an exceptional Weiqi player. He was very hairy, with a faceful of yellow beard Cao Zhang accompanied his father in conquering north and south and was awarded the title of Duke Yan Ling in 216 A.D., by Cao Cao. . Cao Cao once held on to Zhang's beard and said, 'My son of yellow beard is simply amasing!' When Cao Pi became king in 220 A.D., Cao Zhang was awarded the Duke of Jin.

In the fourth year of Cao Pi's reign (223 A.D.), Cao Pi summoned his brother to the palace. During a casual conversation, Cao Zhang asked his brother if he could see his royal stamp (a symbol of kingship). This got Cao Pi suspicious that his brother was after his throne and decided to kill him. Cao Pi knew that Zhang was his mother Bian Hou's favorite son, therefore he must not make it too obvious. After a few weeks, Pi invited Zhang to a weiqi game during their mother's birthday. The game was very close in the middle game when Pi's servants brought out the poisonous prunes. Pi would pick the unmarked ones that were safe to eat and leave the rest to his brother. When Zhang found out that he was poisoned, he screamed for help. Bian Hou rushed to the scene in bare feet and tried to get water to flush out the poison in Zhang's body. Pi hid all the containers ahead of time and Bian Hou failed to fetch the water, and Zhang dies. In Wei's Chun Qiu, a distorted story was painted by Pi as follows. 'Cao Zhang wanted to see the Emperor's stamp. The Emperor knew about Zhang's ambition and refused to see him. Zhang died of great anger.'