Maintain the original shape and play out the original pose, so that the ally does not doubt and the enemy does not move. Submission and stillness lead to decay.
From a distance, the newly sloughed skin of a cicada looks like the cicada itself. One who wants to catch the cicada may be distracted by the skin while the cicada flees. Thus the idiom points to a method of escape: Maintain the appearance of inaction while taking action in secret.
In warfare, to withdraw is no easier than to advance. A retreating army is exposed to attack from its rear; the retreat may turn into a stampede if the superior enemy forces follow up to attack. Therefore one has to arrange a “surprise retreat” by pulling maintaining the appearance of inaction. In a broader sense, the strategy instructs one to conjure up false appearances for the concealment.