痛心疾首 — “To feel extreme pain, grief, and indignation”

During the Spring and Autumn Period, the states of Qin and Jin had a marital alliance, and Duke Mu of Qin had helped Jin secure its throne three times. However, as their territories bordered each other, both states sought to expand their power, inevitably leading to conflicts.

After Duke Li of Jin ascended the throne, due to border disputes, the rulers of Qin and Jin established an alliance at Linghu. But upon returning to Qin, Duke Huan of Qin immediately betrayed the agreement by secretly forming an alliance with the state of Chu.

Concurrently, he compelled Jin to join Qin in attacking Bai Di, a smaller state on Qin's border. Jin agreed, yet Qin secretly informed Bai Di, "Jin is going to attack you."

Both Bai Di and Chu saw through Qin's manipulative intentions and deeply resented Qin's perfidy. They consequently reported Qin's actions to Jin. Jin then assembled the armies of its allied states to confront Qin. At the same time, it dispatched Lü Xiang to sever diplomatic relations with Qin.

Lü Xiang declared, "All the feudal lords now understand that Qin is solely driven by profit and lacks trustworthiness. They are all utterly indignant and heartbroken, wishing to draw closer to Jin. We now stand arrayed in battle. If Qin is willing to swear an oath with us, we will withdraw our allied forces; otherwise, our confederated states will jointly oppose Qin."

One month later, the two armies engaged, and Qin suffered a crushing defeat.