In 239 AD, Emperor Ming of Wei, Cao Rui, lay dying. He entrusted his eight-year-old crown prince, Cao Fang, to two men: Grand Commandant Sima Yi and General-in-Chief Cao Shuang.
After Emperor Ming died, Cao Fang ascended the throne, with Sima Yi and Cao Shuang jointly managing court affairs. Sima Yi, highly respected for his virtue, kept Cao Shuang from acting arbitrarily, and the two coexisted peacefully. However, Cao Shuang later promoted He Yan, Deng Yang, and others to key positions. For their own gain, they often advised Cao Shuang to sideline Sima Yi. Encouraged by them, Cao Shuang gradually grew arrogant.
Cao Shuang, after careful scheming, petitioned the emperor to appoint Sima Yi as Grand Tutor—a promotion in title but a demotion in power, effectively stripping him of his role in state affairs. From that moment, a bitter struggle for control began.
Cao Shuang, confident in his grip on power, grew increasingly reckless, decorating his home like an imperial palace and dressing as if he were the emperor himself. Sima Yi, however, was a master of strategy, often claiming illness to skip court and feigning indifference to all affairs. Yet in secret, he dispatched agents to closely monitor every move in the court, preparing for the moment to strike.
In the winter of 248 AD, Li Sheng, a trusted aide of the powerful regent Cao Shuang, was appointed governor of Jingzhou. Before departing, Cao Shuang ordered him to visit the Grand Tutor's residence to bid farewell—and secretly probe the old man's true condition. Li Sheng arrived at the home of Sima Yi, the veteran strategist feigning illness. Two maidservants helped the frail-looking Sima Yi to his feet, but he deliberately let his robe slip, pretending to be too weak to hold it. Pointing to his mouth, Sima Yi gasped, "I am parched." When a maid brought porridge, he spilled it all over his chest, unable to feed himself. Feigning concern, Li Sheng said, "Everyone says your health has declined, but I never imagined it would come to this." Sima Yi wheezed, "I am old and sickly, death is near. You are heading to Bingzhou—take care." Li Sheng corrected him, "I am bound for Jingzhou, not Bingzhou." Sima Yi squinted, "Oh, Bingzhou..." Li Sheng repeated, "Jingzhou." Sima Yi chuckled weakly, "I am so old and muddled, I misheard. Well, when you reach Jingzhou, build a fine reputation." After Li Sheng left, he reported to Cao Shuang, "Sima Yi is a walking corpse, no cause for worry." Cao Shuang relaxed his guard completely, never suspecting that the feeble old man was secretly plotting the coup that would soon wipe out his entire clan. This story reminds us that appearances can be the deadliest of deceptions.
When Li Sheng visited the Grand Tutor's residence, he found Sima Yi reclining on a lounge chair, supported by two maidservants. As they fed him congee, the soup dribbled down his chin before he could swallow, soaking the front of his robe.
Li Sheng told Sima Yi that he was going to Jingzhou as governor and had come specially to bid farewell. Sima Yi slightly opened his eyes and said haltingly, "You're going to Bingzhou? That's a border region—you must take care of the defenses."
Li Sheng corrected him, saying, "It's not Bingzhou, it's Jingzhou." Sima Yi apologized, replying, "I am old, deaf and blind, no longer of use. The nation's hopes rest on you." After taking his leave, Li Sheng returned and reported to Cao Shuang, "Sima Yi is now nothing but a corpse with a lingering breath, barely holding on. You need not worry about him anymore."
Cao Shuang was overjoyed and let his guard down completely against Sima Yi.
On February 5, 249 AD, Sima Yi seized the opportunity when the emperor led Cao Shuang and others to the outskirts for ancestral tomb rituals, mobilized troops to occupy the armory, and submitted a memorial to the emperor enumerating Cao Shuang's crimes of betraying the late emperor and rebelling, using the charge of "conspiring to revolt" to wipe out the Cao clan and their associates.
On February 9th of that year, Cao and his entire faction were paraded to the Eastern Market and publicly beheaded.
Later, people used the idiom "Corpse-Dwelling with Lingering Breath" to describe someone in extreme decline, on the verge of death.
Source: *Book of Jin*, "Biography of Emperor Xuan"
Meaning of the Idiom: Later, the Chinese idiom "尸居余气" came to describe how someone in extreme decline, on the verge of death.