In the Three Kingdoms period, during a battle between Cao Cao and Liu Bei, Liu Bei ordered his generals Zhao Yun and Huang Zhong to capture Cao Cao's supplies. In response, Cao Cao led a large force to attack Zhao Yun. Zhao Yun retreated to his camp gates, where he ordered his soldiers to lower the banners, silence the war drums, and leave the gates wide open. He then stationed his troops in ambush nearby. When Cao Cao arrived and saw the scene, he immediately suspected a trap and withdrew his forces.
This idiom is now used metaphorically to mean halting an attack or ceasing all activities.