During the reign of Emperor Xian of Han, Liu Biao dominated the Jianghan region, his territory expanding to thousands of li with an army of over a hundred thousand. In his youth, Liu Biao was hailed as one of the Eight Talents, known for his striking appearance and dignified bearing. Yet beneath his scholarly exterior lay a deeply suspicious heart; he loved discussing strategies but often failed to make decisive moves, and though he excelled at gathering talented individuals, he could never fully trust or utilize their abilities.
During the standoff between Cao Cao and Yuan Shao at Guandu, Yuan Shao sent a messenger to seek aid from Liu Biao. Liu Biao outwardly agreed but secretly had his own plans—he would neither send troops to support Yuan Shao nor assist Cao Cao. He aimed to hold the region between the Yangtze and Han Rivers, biding his time to see how the situation unfolded. His generals Han Song and Liu Xian advised him, "In this time of chaos, heroes rise everywhere. The fate of the realm hinges on your decision as Yuan Shao and Cao Cao lock horns. If you wish to make a move, seize the moment when they are both exhausted and weakened. Otherwise, choose a side. You command a formidable army of a hundred thousand, yet you sit idle, watching the tigers fight from the mountain—this is a missed opportunity. Mediation between Cao and Yuan is impossible. If you refuse to aid the capable Cao Cao and ignore Yuan Shao's overtures for alliance, both will resent you. Neutrality is not an option."
"Liu Biao asked, 'What do you think should be done?'"
Han Song advised, 'In my view, with Cao Cao's intelligence and talent, he will surely achieve great things. All the worthy scholars and heroes under heaven are rallying to him. As he grows stronger, he will inevitably destroy Yuan Shao, then march straight to the Jiang-Han region. By then, I fear you, General, will have no strength to resist. So for your sake, it would be better to submit to Cao Cao now. He will surely be grateful and treat you generously. Then you can enjoy lasting wealth and honor, and pass it down to your descendants—this is the safest plan.'
Liu Biao's general Kuai Yue also urged him to side with Cao Cao, but Liu Biao hesitated, unable to make up his mind, so he sent Han Song to observe Cao Cao's true intentions.
When Han Song returned, he praised Cao Cao's reputation and virtue, urging Liu Biao to send his son as a hostage to pledge allegiance. Liu Biao, suspecting Han Song had turned into Cao Cao's advocate, flew into a rage and ordered his execution. Unfazed, Han Song declared, "You have wronged me, General, but I have not wronged you!" This bold statement dispelled Liu Biao's doubts, convincing him of Han Song's unwavering loyalty.
Later, the idiom "a foolproof plan" came to be used to describe an extremely thorough and reliable strategy.
Source: *Records of the Three Kingdoms*, "Biography of Liu Biao"
Meaning of the Idiom: Later, the Chinese idiom "万全之策" came to describe an extremely thorough and reliable strategy.