间不容发 — “The situation is extremely critical or precarious”

During the Western Han Dynasty, Mei Cheng, a renowned poet and official, served as an advisor to Prince Liu Bi of Wu. Observing Liu Bi's increasing ambition to rebel against the central government, Mei Cheng wrote a memorial to strongly advise against it.

Liu Bi was a nephew of Emperor Gaozu, the founder of the Han Dynasty. After establishing the empire, Emperor Gaozu enfeoffed his relatives as kings with significant power. Over time, these powerful regional kings became a severe threat to the imperial court. Consequently, Emperors Wen and Jing gradually reduced the land and power of these kingdoms. Liu Bi resented this policy and began plotting a rebellion, which deeply concerned Mei Cheng.

In his memorial, Mei Cheng analyzed the dire consequences of rebellion. He used an analogy: if a heavy object, say 30 jun (an ancient weight unit), were suspended by a single thread over a bottomless abyss, even the most foolish person would recognize the extreme danger. He further elaborated, imagining beating a drum to startle an already frightened horse, or adding more weight to a thread that is about to snap. The inevitable outcome, he argued, would be the thread breaking in mid-air and the horse plunging into the abyss, beyond rescue. He likened the gravity of such a perilous situation to being so close that there was no space for even a single hair between two objects.

Despite Mei Cheng and other advisors' repeated warnings, Prince Liu Bi ignored their counsel and proceeded with his rebellion plans. Seeing their advice unheeded, Mei Cheng and others left Liu Bi and sought refuge with Prince Liu Wu of Liang.