The crisis began when Yong Lin, a minister of the state of Qi, assassinated the reigning Duke Gongsun Wuzhi. Two princes in exile immediately became contenders for the empty throne. Prince Xiaobai, living in the neighboring state of Ju, had the support of Qi's prime minister Gao Xi, who secretly invited him home. But word also reached the state of Lu, where Xiaobai's older brother Gongzi Jiu had taken refuge. Duke Zhuang of Lu dispatched troops to escort Jiu back to Qi and claim the throne. He also sent Jiu's tutor, Guan Zhong, with soldiers to intercept Xiaobai along the road. It became a race -- two princes converging on the same capital from different directions, each backed by a foreign army.

Guan Zhong caught up with Xiaobai and fired the arrow that should have ended the contest. When Xiaobai fell, apparently dead, Guan Zhong reported his success and the Lu escort force slowed its pace, believing the matter settled. They did not realize that Xiaobai had survived -- the bronze buckle had saved his life, and his theatrical death scene had bought him six critical days. By the time the Lu forces finally reached Qi's capital, Xiaobai had already entered the city, claimed the throne, and been installed as duke. He would become known to history as Duke Huan of Qi, one of the most consequential rulers of the Spring and Autumn period.

Duke Zhuang of Lu was furious. In the late summer of 685 BCE, he personally led an army into Qi to unseat the newly installed duke and place Gongzi Jiu on the throne instead. The two armies met at Qianshi on August 8, the Gengsheng day of the eighth month. The battle was decisive. Qi's forces routed the invading Lu army so thoroughly that Duke Zhuang had to abandon his chariot and flee on a lighter carriage, leaving his men Qinzi and Liangzi behind as decoys. The victory secured Duke Huan's throne and gave Qi the leverage to dictate terms to its defeated neighbor.

The battle's aftermath produced one of antiquity's most remarkable acts of political pragmatism. The victorious minister Bao Shuya led Qi's army into Lu territory and demanded that Duke Zhuang execute Gongzi Jiu and surrender Guan Zhong -- the very man who had tried to kill Duke Huan with an arrow. Duke Zhuang complied. Jiu was killed, and his loyal retainer Shao Hu committed suicide rather than face capture. But when Guan Zhong was brought before the Qi court, Bao Shuya did something unexpected: he recommended that the duke make his would-be assassin chancellor. "Guan Zhong's talent for governing surpasses that of Gao Xi," he argued. Duke Huan agreed. Under Guan Zhong's chancellorship, Qi grew steadily more powerful, until in 667 BCE Duke Huan was formally recognized as the first Hegemon of the Zhou -- the supreme leader among all the feudal states of China.