Repairing the Road While Making a Street Detour

In 205 B.C. Liu Bang was crowned King of Han. But as the military strength of his arch-rival, Xiang Yu was much stronger, Liu Bang was forced to retreat with his 30,000 men to his stronghold of Hanzhong. This area was surrounded by mountains, and the main way to approach it was along a plank road built on the face of a cliff. Liu Bang burned the plank road as soon as his men were safely past it to show Xiang Yu that he had no intention of returning and to prevent pursuit. After about half a year, Liu Bang sent men to rebuild the road, so naturally Xiang Yu thought that an attack was being prepared along that route, and that it would not be forthcoming until the road had been made serviceable again. But meanwhile Liu Bang secretly led a force into Guanzhong by way of the perilous Chencang Pass and caught Xiang Yu by surprise. From then on, Liu Bang began to contend with Xiang Yu for the central parts of China.

Later, the phrase came to be used to describe an obvious action which is camouflage for a devious stratagem.