In the Three Kingdoms Period, during a battle between Cao Cao and Liu Bei, the latter ordered his generals Zhao Yun and Huang Zhong to capture Cao Cao’s supplies.
Cao Cao led a large force against Zhao Yun, who retreated as far as the gates of his camp. There, he ordered that the banners be lowered and the war drums silenced, and that the camp gates be left wide open. Zhao Yun then stationed his troops in ambush nearly. When Cao Cao arrived and saw the situation, he immediately suspected a trap and withdrew his forces.
This idiom (Yan Qi Xi Gu) is nowadays used to indicate halting an attack or ceasing all activities.
【注】camp n. 营寨，帐篷;ambush n. 埋伏;withdrew v. (withdraw的过去时) 撤退