Use case (the fourth discount of Yuan Yiming's Earning Express): "First, it is inconsistent with' building a plank road and crossing the old warehouse in secret'. The second is to kill Zhang Han and other three kings of Qin and seize the land in Guanzhong. "
When Xiang Yu explained the dispute between Chu and Han, relying on his own powerful strength, he called himself the overlord of the West Chu, which violated the agreement that "the one who entered Xianyang first was king, and Liu Bang who entered the customs first was Hanwang". When Liu Bang returned to Hanzhong from Guanzhong from counselor Zhang, he burned the plank road he had walked to show that he would never enter Guanzhong. Later, Liu bang ordered people to rebuild the plank road with the intention of re-entering the customs. General Zhang Han thought it would take a long time to build the plank road, so he didn't care. Unexpectedly, the Han Dynasty led Han Xin's army through secret passages, occupied Chencang and entered Xianyang, according to Guanzhong. The idiom "build a clear path, spend a long time in darkness" is summed up from this historical fact.
Han Xin's Interpretation: A hero of the Han Dynasty helped Xiang Yu at first, and later Zhang and Emperor Gaozu came a long way to praise him. Xiao He visited several times and was invited to build an altar to worship the general, who was the marshal of Chu. Ming Xiu climbed the plank road, secretly crossed Chen Cang, destroyed Qin and Chu, and won every battle. Later, he sealed three kings of Qi and won the world, and most people believed him.
Building a plank road to sneak into Chencang refers to the strategy of frontal attack, luring the enemy to gather and stick to it, confusing the enemy and attacking from the side. This plan is similar to the plan of "introducing from the east to the west", but the difference between them is that "introducing from the east to the west" is a hidden attack site; And "sneaking through Chen Cang" is a hidden attack path. The latter metaphor is often used to hide people's eyes and ears, but to act secretly or do something ulterior.