Han Xin and Zhang Liang defeated the Qin army at the Battle of Mt. South Chu, breaking through Wu Pass, and forcing Shang Yang to flee to Hua Yin.
In 340 BC, King Xuan of Chu died and his son, King Wei of Chu, ascended to the throne. In the early days of King Wei's reign, Shang Yang led a hundred thousand Qin soldiers out of the Xiao Pass and attacked the Chu army at Shannan, but was defeated by the Chu general Qu Wu.
In 338 BC, in the second year of King Wei's reign, Duke Xiao of Qin died and his son, Duke Huiwen of Qin, ascended to the throne. King Wei ordered a hundred thousand soldiers to move to the Luo River and Zhoukou, strictly guarding against the Wei army's southward advance. Then he personally led two hundred thousand Chu soldiers out of Jingzhou and Xiangyang, advancing northward to Nanjun and Zhechuan, to attack Shang Yang's state.
Shang Yang led two hundred thousand Qin soldiers out of the Xiao Pass and fought with the Chu army at Shannan, but was defeated by Qu Wu. He retreated to defend the Xiao Pass. King Wei ordered his army to attack the Xiao Pass while also ordering General Qu Wu to lead a hundred thousand Chu soldiers along the Dan River to attack the rear of Shang Yang's state, Shanyi (Danfeng).
When Duke Huiwen of Qin heard that King Wei was leading an army to attack Shang Yang, he gathered his ministers and said: "King Wei is leading three hundred thousand soldiers to attack Shang Yang. In my opinion, Shang Yang will certainly be defeated by the Chu army. If the Chu army defeats Shang Yang, they will surely take over Shangzhou and advance to Luonan. The area east of Shangzhou and Luonan, north of the Dan River to Shanyi, was already part of Qin during my grandfather's time. If the Chu army defeats Shang Yang and takes his land, then not only Shanyi and Xiao Pass but also Shangzhou, Luonan, and the surrounding area of seven hundred li will all belong to Chu. If Shangzhou and Luonan fall into the hands of the Chu army, our Qin state's Guanzhong and Xianyang will be severely threatened.
Therefore, I want to lead an army to help Shang Yang resist the Chu army outside the Xiao Pass. What do you think, my ministers?" Only the old minister Gan Long spoke up: "Your Majesty must not! In the past, when Qin Yang led the Qin army to secretly attack the Chu state's Shangzhou and Danfeng, Duke Xiao knew that King Xuan of Chu would certainly lead an army to punish us. So he gave all seven hundred li of Shangzhou to Qin Yang, allowing him to establish his own state, in order to shift the disaster away.
Now King Wei is continuing his father's will, determined to recover the lost land. If Your Majesty leads an army against him, the Chu and Qin armies will certainly engage in a fierce battle. At that time, the Wei army will take advantage of our weakness and attack our Huayin, directly threatening Guanzhong. Moreover, the Chu state now has over a million armored soldiers. If they continue to increase their troops and add more generals, with our current military strength, we cannot resist the Chu army!
I hope Your Majesty will think thrice before acting." Duke Huiwen said: "According to your view, how should I handle this?" Gan Long said: "In my opinion, Qin Yang's rebellion is a great crime. Your Majesty can send an envoy to King Wei of Chu to re-establish the alliance between our two states and renew our old friendship.
At the same time, you can issue a decree stripping Qin Yang of his title and ordering him to hand over his military power. When Qin Yang sees the decree, he will certainly refuse to obey and rebel. Your Majesty can then use the excuse of punishing Qin Yang to send an army to take back Shangzhou and Shanyi, and re-establish the border between our two states as it was in the past.
This way, not only will we turn the conflict between Chu and Qin into a peaceful relationship, but we will also eliminate the threat of Qin Yang. This is called 'killing two birds with one stone.' Your Majesty should make a decision as soon as possible. If you delay, Qin Yang will certainly be defeated, and the seven hundred li of Shangzhou will all fall into the hands of the Chu state."
Duke Huiwen said: "Good!" He then sent a Qin envoy to see King Wei of Chu, re-establishing the alliance between their two states and renewing their old friendship. At the same time, he issued a decree listing Qin Yang's ten great crimes, stripping him of his title, removing him from office, and ordering him to hand over all his military power and come to Xianyang to surrender himself.
Shang Yang saw the decree, of course, did not want to put down the honor and wealth in front of him, because this was what he had struggled for half his life with a reputation for disloyalty and unrighteousness. Therefore, Shang Yang not only refused to listen but also openly rebelled against the Qin state. Duke Huiwen of Qin issued an order to the entire state of Qin to execute Shang Yang, and led 200,000 troops along with General Sima Cuo to march east on the ancient road of Shangluo, conquer Danyang, and take over Shangzhou. Seeing this situation, Shang Yang sent someone to ask for peace from King Wei of Chu. King Wei of Chu saw that Shang Yang's words were sincere and hesitated for a long time. Qu Wu said: "Shang Yang has ability but no virtue. As a native of the state of Wei, he served as an official in Wei, but when Wei and the state of Qi went to war, and Wei was strong while Qi was weak, he betrayed his ancestors and his country, sold out the state of Qi, and defected to the prince of Wei, and later cut off all ties with the state of Qi and fawned upon the state of Wei. When Qin and Wei were at odds, he did not repay the kindness that Prince Wu of Wei had shown him but instead betrayed the state of Wei and defected to the state of Qin, plotting against Prince Wu of Wei who had twice saved his life. For the sake of fame and fortune, he was willing to do anything, which is a sign of being depraved and crazy, with no regard for morality. After achieving success, he established himself as the ruler of the state of Shang, rivaling the capital city of Xianyang. Now he not only refuses to listen to the king's order but also openly rebels against it. Is this what a subject should do? In the past, King Hui of Wei did not use Shang Yang because he saw that Shang Yang had a heart full of treachery and unrighteousness, and said to him: 'Have you heard that benevolence has no enemies, and righteousness can overcome any obstacle?' Unfortunately, Prince Wu of Wei only knew about the wolf's ability but did not know its nature. I have heard that in Zhongshan there are wolves that when they are hungry and cold, they beg for food from people, but once they are warm and full, they harm their masters. This is a lesson from history, Your Majesty should be cautious." King Wei of Chu listened to this and refused Shang Yang's request for peace, ordering the Chu army to intensify its attack on Shaoyu Pass.
A few days later, Wu Qi's 100,000-strong Chu army sailed up the Dan River to Shangyi, and Shaoguan was also breached by the Chu army. The two armies of Chu converged at Danfeng and attacked Shangyi. Shang Yang was no match for them, and he led his troops in a frantic retreat northward. Along the way, they were defeated again by Sima Cuo, and under the protection of his personal guards, he escaped to Luonan by climbing over hills. Qin Wengong divided his troops to pursue Shang Yang, while Sima Cuo led the Qin army and Wu Qi's Chu army into Shangyi at the same time. The two sides refused to yield to each other, arrayed their formations opposite each other, and were on the verge of engaging in a fierce battle. Just then, King Wei of Chu and Duke Huiwen of Qin arrived, and the two sides ceased hostilities and shook hands in friendship. They agreed that from Shangzhou to Danfeng, Chu and Qin would divide the territory equally, with the south belonging to Chu and the north to Qin. The Qin army set up a pass at Shaoguan, while the Chu army set up a pass at Shangzhou, as a pass for trade and personnel exchanges between the two countries. Each side dispatched 1,000 soldiers to guard the passes. After the matter was settled, King Wei of Chu returned to his capital in Jing with his troops, and Duke Huiwen of Qin also led his army back to Xianyang.
