This entry explains the cautionary Chinese idiom 暗箭难防(àn jiàn nán fang) . It warns that covert underhanded attacks are hard to defend against, covering its proverbial couplet, lesson and English equivalents.
This article tells the treachery of Gongsun Zidu, the handsome general of Zheng. Jealous of Ying Kaoshu’s bravery in the Xu campaign, Zidu shot him with a hidden arrow. Tormented by guilt, he confessed and committed suicide, leaving a lasting lesson about hidden betrayal.