程昱
Cao Cao was impressed when he heard about Xu Shu and was eager to recruit Xu as an adviser. He invited Xu Shu's mother to meet him and asked her to write a letter to her son, requesting that her son come to join him. Xu Shu's mother refused, denounced Cao Cao as a treacherous villain, and threw an ink stone at him. The furious Cao Cao ordered Xu Shu's mother to be executed but changed his mind when Cheng Yu reminded him that Xu Shu would be more determined to help Liu Bei oppose him if he killed his mother. Cao Cao then had Xu Shu's mother detained and asked Cheng Yu to pretend to be Xu Shu's sworn brother to win the trust of Xu's mother. After some time, Cheng Yu got close to Xu Shu's mother and learnt to mimic her handwriting. He wrote a letter to Xu Shu in the handwriting of Xu's mother, telling Xu that she was in trouble and urging him to come to the imperial capital Xu (許; present-day Xuchang, Henan) quickly. Xu Shu was a filial son so he immediately left for Xu after reading the letter.