After the Qin Dynasty fell, Xiang Yu, relying on his military might, declared himself Hegemon-King of Western Chu and divided the realm, sending the threatening Liu Bang to the remote Ba, Shu, and Hanzhong regions as the King of Han. To block Liu Bang's eastward advance, Xiang Yu appointed the surrendered Qin general Zhang Han as King of Yong, Sima Xin as King of Sai, and Dong Yi as King of Zhai, granting them lands in the Guanzhong region adjacent to Hanzhong.
Liu Bang, too, harbored ambitions to rule the world, but unable to contend with Xiang Yu for the moment, he was forced to go to Hanzhong's Nanzheng as the King of Han. The journey from Guanzhong to Nanzheng wound through towering mountains and sheer cliffs, with the only passage being a plank road stretching hundreds of li. Along the way, Liu Bang recalled how he had started as a village chief, joined Chen She's uprising against Qin, fought for three years, captured Xianyang, and overthrown the Qin dynasty—only for Xiang Yu to break the promise that whoever entered Xianyang first would rule Guanzhong, exiling him to a remote border region. This thought filled him with bitter indignation.
At this moment, the strategist Zhang Liang asked him, "What are your plans for the future, Your Majesty?" Liu Bang ground his teeth and said, "I must defeat Xiang Yu to avenge this hatred!"
Zhang Liang said, "If that's the case, after our troops pass through, we'll burn the plank road. This will both prevent others from attacking us and mislead Xiang Yu into thinking that Your Majesty has no ambition to seize the Central Plains."
Liu Bang, following Zhang Liang's advice, burned the plank roads to the ground.
After arriving in Nanzheng, Liu Bang rested his troops, sharpened his weapons, and, on the recommendation of his chancellor Xiao He, promoted Han Xin to the rank of general, entrusting him with the military strategy to conquer the realm.
One day, Han Xin said to Liu Bang, "Your Majesty, to unify the empire, you must first seize Guanzhong and open the eastern gate." Liu Bang asked, "The plank road has been burned—how can we attack Guanzhong?"
Han Xin said, "I've already sent scouts to find a small path leading to Chencang in Guanzhong. We can have a few hundred soldiers openly repair the plank road while secretly sending the main force along this path to launch a surprise attack on Chencang..."
Overjoyed, Liu Bang urged Han Xin to set out immediately.
King Yong, Zhang Han, upon hearing that the Han army was repairing the plank road, laughed and said, "A few hundred Han soldiers repairing the plank road—who knows when that will ever be finished? There's nothing to worry about." He continued drinking and feasting all day, completely off guard.
Soon after, Zhang Han received news that Chencang had fallen. He hastily led his troops into battle, but it was too late—defeated, he took his own life. The kings stationed in eastern Guanzhong, Sima Xin of Sai and Dong Yi of Zhai, could not withstand the Han army and surrendered one after another. Liu Bang thus seized control of the Guanzhong region, known as the Three Qin territories.
Later, "Repairing the Plank Road by Day" is often used together with "Advancing on Chencang by Night" to describe using overt actions to mislead and lull the opponent while secretly taking another course to achieve a goal.
Source: *Records of the Grand Historian*, Chapter "Annals of Gaozu"
Meaning of the Idiom: Later, the Chinese idiom "明修栈道" came to describe using overt actions to mislead and lull the opponent while secretly taking another course to achieve a goal.