In the final years of the Qin Dynasty, after Chen Sheng and Wu Guang raised the banner of revolt at Daze Village, peasant uprisings erupted across the land. At that time, Xiang Liang, a descendant of the Chu nobility, and his nephew Xiang Yu were in Wuzhong, where they had rallied many supporters and were preparing to join the rebellion.
Two months after Chen Sheng and Wu Guang launched their uprising, Yin Tong, the governor of Kuaiji Commandery, also planned to raise an army and declare himself ruler. Admiring Xiang Liang's reputation, he summoned both Xiang Liang and his nephew Xiang Yu to his mansion to discuss the matter. Xiang Liang stated, "Now, countless rebel armies have risen against the brutal Qin dynasty across the land. This proves the Qin has lost the people's hearts entirely. This is the perfect moment to destroy them. Those who strike first can control others; those who hesitate will be controlled by others!"
Yin Tong hoped that Xiang Liang, Xiang Yu, and a man named Huan Chu would lead troops together to start a rebellion. But Xiang Liang had no intention of cooperating with Yin Tong, nor did he want to work with Huan Chu, so he made an excuse: "Huan Chu is now in exile, and I do not know where he is. My nephew Xiang Yu knows his whereabouts; let me go and call Xiang Yu in."
Yin Tong agreed. Xiang Liang stepped outside, whispered a few words to Xiang Yu, who nodded and followed him back inside. As Yin Tong began to question Xiang Yu, Xiang Liang gave a signal, and Xiang Yu, catching Yin Tong off guard, struck him down with a single sword stroke.
Immediately, Xiang Liang and Xiang Yu declared an uprising in Wuzhong. Young men from Jiangdong flocked to join their rebel forces. Later, when Xiang Liang fell in battle, Xiang Yu took command, and their army grew into the most formidable force against the Qin dynasty.
Later, the idiom "strike first to gain the upper hand" is used to describe taking the initiative to subdue an opponent.
Source: *Book of Han*, "Biography of Xiang Liang"
Meaning of the Idiom: Later, the Chinese idiom "先发制人" came to describe how taking the initiative to subdue an opponent.