In the Three Kingdoms Period (sān guó shíqī 三国时期,220－280AD). Cao Cao (cáo cāo 曹操)and Liu Bei (liú bèi 刘备) were both considerablly talented leaders of two Kingdoms respectively. In order to gain the final domination of the whole country,they contended with each other usually. They were at war again at that time,Liu Bei ordered his generals Zhao Yun (zhào yún 赵云) and Huang Zhong (huáng zhōng 黄忠) to loot Cao Cao’s food supplies. Rather irritated by it,Cao Cao led on a large force against Zhao Yun,who then retreated swiftly as fas as the gates of his camp. There, he ordered the soldiers to open the gate widely,lower the flags and stop drumming. Zhao Yun then stationed his troops in ambush nearly. When Cao Cao arrived and saw the pretty odd situation, he suspected a trap in an instant and thus withdrew his forces rashily.

This idiom is nowadays used to indicate metaphorically halting an attack or ceasing all activities.

故事发生在三国时期。一次，曹操与刘备交战。刘备命令大将赵云、黄忠去抢夺曹操的粮食。曹操带领大军追赶赵云。赵云边打边退，一直退到营寨前，叫士兵打开营门，放倒军旗，停止擂鼓，在营外设好埋伏。曹军追到，看到这种情景，怀疑有埋伏，就撤退了。

后来，“偃旗息鼓”这个成语就用来比喻停止攻击或者事情中止。

偃旗息鼓 (yǎn qí xī gǔ)
【翻译】to stop clamoring.
【释义】偃：仰卧，引伸为倒下。放倒旗子，停止敲鼓。原指行军时隐蔽行踪，不让敌人觉察。现比喻事情终止或声势减弱。
【例句】这场规模浩大的革命运动受到了政府的强烈镇压，终于偃旗息鼓了。
【近义词】销声匿迹、鸣金收兵
【反义词】大张旗鼓、重整旗鼓