In the fourteenth year of King Zhaoxiang of Qin's reign, the states of Han and Wei launched successive attacks on Qin. With Qin's available forces numbering less than half the enemy's, the situation grew dire. The king ordered the veteran general Bai Qi, who had won many battles, to lead the army and face the combined forces of Han and Wei at a place called Yique.
In truth, the states of Han and Wei were not united. The ruler of Han had only been on the throne for three years, his kingdom not yet strong enough, and he hoped Wei's army would engage Qin first while preserving his own forces. Wei, for its part, saw the campaign as Han's initiative and wanted to reap the rewards without bearing the brunt of battle. Thus, each state, prioritizing its own interests, let the perfect opportunity slip away.
Bai Qi deployed a decoy force to keep the Han army pinned and afraid to engage, while he concentrated his main troops and launched a surprise attack that crushed the Wei army. With the Qin forces now riding a wave of morale—banners fluttering, war drums pounding, and battle cries shaking the fields—the Han soldiers were terrified. The moment they clashed, they broke ranks, threw down their armor, and fled for their lives. Bai Qi led the pursuit, cutting down the routed soldiers, and the Qin army won a decisive victory.
The idiom "Riding Victory, Chasing the Defeated" means pursuing fleeing enemies after a victory. "Defeated" refers to those who have lost.
Source: *Strategies of the Warring States*, Chapter "Strategies of Zhongshan"
Meaning of the Idiom: Later, the Chinese idiom "乘胜逐北" came to describe pursuing fleeing enemies after a victory.