During the Warring States period, King Zhaoxiang of Qin ordered his great general Bai Qi to defeat the states of Han and Wei, then commanded Bai Qi to attack Chu, calling on Han and Wei to send troops as well.
During the Warring States period, Lord Chunshen of Chu, named Huang Xie, was on a diplomatic mission in Qin. When he learned that King Qingxiang of Chu was gravely ill and his heir might be in danger, he rushed to see King Zhao of Qin. With urgency, he pleaded, "Your Majesty, if the King of Chu passes away and his successor is not secured, your ally Chu may fall into chaos. Allow me to return at once to stabilize the situation—this will serve both our kingdoms." King Zhao of Qin, seeing the logic, granted his request. Lord Chunshen then swiftly returned to Chu, ensuring a smooth succession and earning lasting renown for his loyalty and quick thinking.
"Your Majesty, you are playing the role of the snipe and the clam locked in a struggle, with the fisherman reaping the reward!" Lord Chunshen declared. King Zhao asked, "What do you mean by that, sir?" Lord Chunshen replied, "Today, Qin and Chu are the two strongest states under heaven. If they go to war, it will be like two tigers fighting, and the ones to profit will be Han, Wei, and Qi." King Zhao interjected, "But Han and Wei have just been defeated by our Qin—what tricks can they still pull?"
Lord Chunshen said, "Han and Wei have generations of enmity with your Qin. Over a dozen of their royal family members died as hostages in Qin—they will never forget that vengeance. If they join this attack on Chu, it's only because Qin forced them. If the Qin-Chu battle reaches a stalemate, Han and Wei will seize Chu's lands and destroy Song, while Qi will grab the Si River region. So in my view, this campaign is actually helping those three states expand their territory, giving them the strength to challenge Qin in the future."
King Zhao found Huang Xie's reasoning sound, so he ordered Bai Qi to halt the attack and sent an envoy with gifts to Chu, forming an alliance with the state.
Later, the idiom "Two Tigers Fighting" came to be used as a metaphor for two powerful sides locked in conflict.
Source: *Records of the Grand Historian*, "Biography of Lord Chunshen"
Meaning of the Idiom: Later, the Chinese idiom "两虎相斗" came to describe a metaphor for two powerful sides locked in conflict.