During the late Eastern Han Dynasty, as warlords clashed across the land, a learned scholar named Xu Shu from Yingchuan sought out Liu Bei, who was then stationed in Xinye after a defeat. Xu Shu presented himself and was appointed as Liu Bei's military advisor.
Soon after, Cao Cao sent a massive army to attack Xinye, only to suffer a crushing defeat due to Xu Shu's clever strategy. Learning that Xu Shu served as Liu Bei's advisor, Cao Cao greatly admired his talent and desperately wanted to lure him away, hoping Xu Shu would instead devise plans for him.
Advisor Cheng Yu proposed, "Xu Shu is deeply devoted to his mother. If we lure her here, he will surely pledge allegiance."
Cao Cao, delighted, devised a plan: he first lured Xu Shu's mother to Xuchang and placed her under house arrest, then forged a letter in her handwriting, sending it to Xu Shu with the message, "Come to Xuchang at once."
Upon receiving the letter, Xu Shu believed it was truly his mother's handwriting. Fearing she might face harm in Xuchang, he reluctantly told Liu Bei, "I originally wished to join you in building a great enterprise, relying entirely on my loyal heart. But now Cao Cao has taken my mother hostage. My mind is in turmoil, and staying by your side would serve no purpose. Please allow me to take my leave."
Though deeply reluctant, Liu Bei had no choice but to reluctantly agree. Xu Shu then bid farewell to Liu Bei and set out for Xuchang. Only upon arriving there did he realize he had been deceived.
Later, the idiom "fang cun yi luan" came to describe a state of utter mental confusion, not knowing what to do.
Source: *Records of the Three Kingdoms*, "Biography of Zhuge Liang"
Meaning of the Idiom: Later, the Chinese idiom "方寸已乱" came to describe a state of utter mental confusion, not knowing what to do.