Attack the enemy with two convergent forces. The first is the direct attack, one that is obvious and for which the enemy prepares his defense. The second is the indirect, the attack sinister, that the enemy does not expect and which causes him to divide his forces at the last minute leading to confusion and disaster.

It always used to describe someting private.

This stratagem took place towards the end of the Qin dynasty. There were rebellions everywhere and the most powerful of the rebel leaders was Xiang Yu, warlord of Western Chu.

Xiang Yu appointed Liu Bang as king of Hanzhong, effectively making him leave China. To further ensure that Liu Bang does not return to China from the East, Xiang Yu divided Guanzhong into three principilities and put three people in charge, informing them to be alert against Liu Bang.

Liu Bang's aide Zhang Liang said, "In order to placate Xiang Yu and the three kings, we must destroy the mountain plank road to show that we've no intention of returning to China."

Once Liu Bang arrived in Hanzhong, he made Han Xin commander of his army. After nine years of preparations, Liu Bang's army became powerful and was ready to march eastwards.

On Han Xin's suggestion, Liu Bang ordered his generals Fan Hui and Zhou Bo to take 10,000 men and horses and repair the plank road within three months. The scale of the job was large, they repaired only a few li* in three months, which was too slow.

Liu Bang recalled Fan Hui and Zhou Bo and placed others in charge of the task. Meanwhile, his enemies were greatly perturbed. One of the kings even led his forces to block the plank road exit.

Han Xin then led Fan Hui, Zhou Bo and several thousand troops to overrun Guanzhong by the old roundabout route through Chencang.