Zhang Liang's ancestors were from the state of Han. Twenty years after his father's death, the Qin state conquered Han, and Zhang Liang vowed revenge.
Zhang Liang recruited a powerful strongman and forged an iron mallet weighing 120 jin. When the First Emperor of Qin toured the eastern territories, Zhang Liang and the strongman ambushed him at the Bolang River, striking with the iron mallet but mistakenly hitting the emperor's decoy carriage. The First Emperor flew into a rage and launched a massive manhunt across the empire. Zhang Liang changed his name and fled into hiding at Xiapi.
After Zhang Liang joined Liu Bang (then known as the Duke of Pei), he repeatedly presented strategic proposals based on *The Art of War of Taigong*, and Liu Bang frequently adopted his plans.
When Zhang Liang followed Pei Gong (the future Han Gaozu) in leading troops to a decisive victory over the Qin army and entered the Qin palace, Pei Gong was captivated by the countless treasures and beautiful women inside and refused to leave. Zhang Liang admonished him, "It was precisely because the Qin dynasty was tyrannical and unjust that you, Pei Gong, were able to come here. We should uphold integrity and simplicity. If you indulge in pleasure upon entering the Qin capital, that would be 'helping Jie to do evil'—aiding a tyrant in his wickedness." Heeding Zhang Liang's words, Pei Gong left the palace and stationed his army at Bashang. This idiom now describes helping a villain commit evil deeds.
Source: *Records of the Grand Historian*, "Biography of the Marquis of Liu"
Meaning of the Idiom: Later, the Chinese idiom "助桀为虐" came to describe helping a villain commit evil deeds.