In the Battle of Chengpu between Jin and Chu, the state of Jin decisively defeated the Chu army and became the hegemon of the Central Plains. Afterwards, Jin repeatedly convened alliances among the feudal lords; Chen, Cai, and Zheng, which had originally been vassals of Chu, seeing Jin's strength, also defected to Jin and joined the alliance. However, the state of Zheng acted duplicitously—despite knowing it had a covenant with Jin, it secretly formed an alliance with Chu out of fear of Chu.
After learning of this, Duke Wen of Jin planned to convene the feudal lords to attack Zheng. His ministers believed that Jin's own forces were sufficient to deal with Zheng and that there was no need to trouble the other lords. Duke Wen had previously agreed with Qin to cooperate in military campaigns, so he only notified Qin. Duke Mu of Qin, eager to expand eastward, personally led his troops to Zheng upon receiving the message, and they camped on the eastern and western sides of Zheng's capital respectively. With the two most powerful states of the time, Qin and Jin, at its gates, Duke Mu of Zheng was terrified and at a loss, quickly sending the eloquent Zhu Zhiwu to persuade the Qin army to withdraw. Zhu Zhiwu analyzed for Duke Mu of Qin that Zheng was a neighbor of Jin, and if Qin and Jin destroyed Zheng, Jin would become even stronger. After that, Jin might even invade Qin to the west, so Qin would gain nothing. He then suggested that if Qin made peace with Zheng, in future dealings between Qin and Jin, Zheng could host Qin's envoys. Duke Mu of Qin found this reasonable, made a separate peace with Zheng, left three generals with two thousand troops to guard Zheng's northern gate, and quietly led the rest of his army back home.
The Jin army, discovering that the Qin forces had quietly withdrawn, was furious. Although Duke Wen of Jin, having once received favors from Duke Mu of Qin, did not pursue them, he nonetheless launched a fierce assault on the capital of Zheng. Seeing that Qin had retreated but Jin continued its attack, Zheng had no choice but to send envoys to the Jin camp to plead for surrender. Once Duke Wen of Jin accepted Zheng's submission, he brought Zheng over to his side, formed an alliance with them, and then withdrew his troops. When Duke Mu of Qin learned that Zheng had defected to Jin, he was angered, but unwilling to damage his relationship with Jin, he refrained from launching another campaign against Zheng.
In 628 BCE, Duke Wen of Zheng passed away, and Prince Lan succeeded to the throne as Duke Mu of Zheng. That winter, Duke Wen of Jin also died, and his son Duke Xiang of Jin took over. Duke Mu of Qin felt it was time to contend with Jin for supremacy and pursue his ambitions of hegemony. Meanwhile, the Qin general Qizi, who had been stationed in Zheng, secretly sent a message to Duke Mu of Qin, saying that they had already obtained the keys to Zheng's northern gate and that a surprise attack would surely succeed. Jian Shu and Bai Li Xi believed that launching a distant expedition would inevitably alert the enemy and lead to failure, advising Duke Mu of Qin against it. However, Duke Mu of Qin had made up his mind and refused to heed the advice of his two veteran ministers. He appointed Bai Li Xi's son Meng Ming Shi as the chief general, and Jian Shu's sons Xi Qi Shu and Bai Yi Bing as deputy generals, leading 400 war chariots to launch a surprise attack on Zheng. Foreseeing that this campaign was doomed to fail and that their sons might never return, Jian Shu and Bai Li Xi wept as they saw the troops off.
The Qin army marched eastward through the Zhou region and in February 627 BC entered the territory of Hua (in present-day Henan Province), which was still 80 kilometers from the state of Zheng. A Zheng merchant named Xian Gao, who frequently traveled between states for trade, was driving cattle to Luoyi to sell when he happened upon the long-distance raiding Qin army. He discussed with his companions, saying that the Qin army had marched through various vassal states to get here, clearly intending to launch a surprise attack on Zheng while it was unprepared, but there was no time to report back to Zheng. So he immediately sent someone to rush back to Zheng overnight to inform Duke Mu of Zheng, while he drove his cattle herd to the Qin army camp, falsely claiming to be an envoy sent by Zheng and requesting to see the Qin commander.
The Qin army had originally planned to launch a surprise attack on the state of Zheng, but now that Zheng had actually sent an envoy to their camp, Meng Mingshi was somewhat startled and personally received this man who claimed to be an envoy. Xian Gao said to Meng Mingshi that he had been ordered by the ruler of Zheng to come specifically with gifts to reward the Qin army, and then he presented four tanned cowhides and twelve fat cattle.
The envoy from the state of Zheng had traveled a great distance to reward the Qin army, which made it clear that Zheng already knew of the impending attack and had prepared for it, making a surprise assault impossible. Consequently, Meng Mingshi immediately changed his plan, canceled the attack on Zheng, and led his troops back to the state of Qin.
After Duke Mu of Zheng received news that the Qin army was planning a surprise attack, he immediately ordered preparations for battle and sent someone to observe the Qin troops guarding the northern gate, discovering that they were armed and ready for combat. The Zheng minister Huang Wuzi then issued an expulsion order to the three Qin generals. Realizing their plan had been exposed and Zheng was already prepared, the generals knew they could no longer stay, so they led their troops away that very night.
Because of Xian Gao's quick thinking, the State of Zheng avoided being destroyed by the State of Qin, and both Duke Mu of Zheng and the people were deeply grateful to him. The duke wanted to reward Xian Gao's patriotic act with high office and generous gifts, but Xian Gao said that loyalty to one's country was only natural, and that accepting such rewards would make him seem like an outsider, so he firmly refused. The patriotic story of Xian Gao's clever ruse to reward the Qin army has been passed down ever since.