Xu Shu was one of Liu Bei's advisors during the Three Kingdoms era of China. He helped to provide strategies against Cao Cao when he attacked Liu Bei. It was he who defeated Cao Cao's army led by Cao Ren. Cao Cao had long admired the man, and wishing to lure Xu Shu into his service he captured his mother and took her to the capital. There Cao Cao's advisors wrote a fake letter pretending to be Xu Shu's mother saying how she wanted him to be there with her and her suffering. Xu Shu was known to be a man of strong filial piety and left to find her though he promised never to serve Cao Cao.
When he went to his mother, she was outraged and hung herself. Xu Shu kept his promise and did not advise Cao Cao. Just before the Battle of Red Cliffs, however, he was in Cao Cao's camp when Pang Tong advised Cao Cao to tie the ships together with chains to prevent sea sickness among his soldiers. Xu Shu saw at once that this was to assist Zhou Yu's fire attack against Cao Cao's fleet. Xu Shu asked Pang Tong how to escape, and the latter told him to spread the rumour that Ma Teng and Han Sui were leading a rebellion against Cao Cao. Cao Cao commanded Xu Shu to subdue the rebellion. Xu Shu therefore managed to escape from the battle.
Prior to leaving Liu Bei, Xu Shu recommended that he seek out Zhuge Liang, who would become Liu Bei's most indispensable and trusted advisor.