During the Warring States period, the states of Han and Wei had been locked in battle for over a year with no clear victor. King Hui of Qin wanted to intervene but was torn after his ministers gave conflicting advice—some said it would benefit Qin, others warned against it. Just then, Chen Zhen of Chu arrived as an envoy. A seasoned strategist who had once served alongside Qin's current prime minister Zhang Yi, Chen Zhen was known for his sharp mind. King Hui of Qin asked for his counsel. Chen Zhen replied, "Your Majesty, have you heard of the farmer who saw a hare dash into a tree stump and break its neck? Delighted, he abandoned his plow and waited by that stump every day, hoping for another hare—but never caught one, and became a laughingstock. Now, if Qin attacks based on the uncertain outcome of Han and Wei's war, you risk the same folly." King Hui of Qin heeded the warning and held back. This story gave rise to the idiom "waiting by the stump for a hare," a caution against clinging to past luck instead of adapting to changing circumstances.
Chen Zhen then told King Hui of Qin the story of Bian Zhuangzi stabbing the tiger:
Bian Zhuangzi (or Guan Zhuangzi, a traveler staying at an inn) once saw two tigers tearing apart a cow and drew his sword to attack them. The innkeeper stopped him, saying, "Those tigers are eating the cow—when they get a taste, they'll fight over it, and in the fight, the big one will be wounded and the small one killed. Then you can stab the wounded tiger and earn the fame of killing both with one blow." Bian Zhuangzi thought this wise and waited. Soon, the tigers fought; the smaller one died, and the larger one was badly mauled. Bian Zhuangzi then struck the wounded tiger with his sword, winning the glory of slaying both beasts in a single effort. Source: *Strategies of the Warring States*, "Strategy of Qin"
After finishing his story, Chen Zhen continued, "Today, Han and Wei have been at war for over a year. Inevitably, the smaller state will be destroyed, and the larger one will be exhausted. Attacking the weakened victor then would defeat both at once—just like Zhuangzi stabbing the tigers!"
King Hui of Qin was greatly impressed and ultimately decided to hold off on sending troops, choosing instead to sit on the mountain and watch the tigers fight.
From this story, the idiom "Both Sides Suffer" emerged, describing a conflict where both parties are harmed. Another idiom, "When Two Tigers Fight, One Will Be Hurt," also derived from it, meaning that when two powerful forces clash, one side will inevitably be weakened.
Source: *Records of the Grand Historian*, "Biography of Zhang Yi"
Meaning of the Idiom: Later, the Chinese idiom "两败俱伤" came to describe how when two powerful forces clash one side will inevitably be weakened.