Explaination: The cicada sheds its skin intact, so that the shell looks like a real cicada. Similarly, outnumbered generals or those who were targets for assassination created false impersonations of themselves to escape danger. When use it for military affairs, you can create the illusion that you are where your opponent expects you to be. Meanwhile, you can put your energies into your real plans.
Related story
The warlord Cao Cao of Wei, was pursuing the fleeing army and population of Shu led by the heroes of the Peach Grove, Liu Pei and Chang Fei. The retreating column came upon the Changpan bridge over the Wei river with the enemy army only hours behind. On the opposite side of the river there was heavy forest. Chang Fei turned to his general Liu Pei and said: "This bridge is the only crossing point for miles and provides us with an advantage. You take the army and people across while I hold off the Wei army to give you as much of a lead as possible." After the Shu army had crossed over, Chang Fei sent his small group of cavalrymen across the bridge into the forest where they tied branches to their horses tails and rode around in circles. Chang Fei remained sitting on his charger in the middle of the bridge. When the pursuing army of Wei came upon the sight of Chang Fei alone on the bridge they stopped. Cao Cao noticed the huge dust cloud in the distance behind the woods and suspected a trap. Chang Fei roared out a challenge to the Wei army but Cao Cao, now convinced this was a ruse, turned his men around to retreat. Chang Fei seeing the Wei army turn about spurred his charger towards the Wei as though to attack them single handedly. This so unnerved the Wei forces that they made a mad scramble to escape the area convinced a trap was closing around them. This trick bought Lui Pei and Chang Fei enough time to escape with their men and regroup at Chianling.