Zhan Huchang's Chu army defeated the Wei army, establishing military merit for Qin Shuang and forming a friendly alliance.

  In the 16th year of Chu Xuan Wang, Wei Huiwen Wang launched a southern invasion and clashed with the Chu army south of Xuchang and northwest of Yu State's Fanglei and Ye. Both sides deployed 200,000 troops each. The Chu army was defeated by the Wei forces south of Xuchang. Han Ai Hou sent 100,000 troops to assist the Wei army in attacking the Chu forces. Seeing this, Chu Xuan Wang retreated to defend Fang and Ye, while Ruzhou, Yuzhou, and Gucheng were occupied by the Han and Wei armies.

  Wei Yang took advantage of the situation and led the Qin army eastward, defeating the Wei army at Huayin in western Henan. The Qin army then marched towards Tongguan, Hancheng, and Anyi. At that time, the main force of the Wei army was stuck in a stalemate with the Chu forces at Xuchang and Yuzhou, leaving the defenses of Huayin and western Henan relatively weak.

  Upon hearing the news, Wei Huiwen Wang hastily dispatched 200,000 troops from Jincheng and Jinzhong to Anyi. The Qin army was defeated by the Wei forces at Hancheng and Tongguan, forcing them to retreat. Wei Yang then led his army southward to attack the Han forces in Luochuan, expanding their territory north of Shangnan.

  In the 27th year of Chu Xuan Wang, that is, in 343 BC, King Huiwen of Wei ordered his general Pang Juan to lead an army of 300,000 soldiers to attack Zhao and Qi. The king of Qi, using Sun Bin's tactics of feigning weakness and luring the enemy deep into his territory, defeated Pang Juan at the Battle of Maling, almost annihilating the entire Wei army.

  As a result of this defeat, the state of Wei was severely weakened, having already been exhausted by years of continuous warfare. The position of King Huiwen as the dominant power in the land began to shake, and the king of Qi became even more arrogant, thinking that he was the only one who could be the dominant power.

  Qin Xiao took advantage of this opportunity to lead an army of 200,000 soldiers eastward to attack the Wei army, with the intention of capturing the western part of the Yellow River from Wei. The Zhao army also took advantage of the situation and launched a full-scale attack on Wei's An Yang.

  King Huiwen of Wei faced with the invasion of the armies of Qi, Zhao, and Qin, ordered his generals to lead their troops to fight against the enemy. He himself led an army to fight against the Zhao army from Handan. However, due to the defeat of Wei Gongzi Rang at Huaxin in the west of the Yellow River, who was deceived by Wei Yang, he had to cede territory to Qi and give up An Yang to Zhao in order to seek peace.

  Alas! The state of Wei had just suffered a great defeat at Maling, with tens of thousands of soldiers killed or wounded. Now it had again been defeated at Huaxin, losing another 100,000 soldiers, and its national strength was declining year by year.

  Wei Gongzi Ao was a close friend of Wei Yang, and in the past, when Wei Yang was down on his luck, Wei Gongzi Ao provided him with great help and support. Without Wei Gongzi Ao's assistance, Wei Yang would have long since starved to death on the streets of Wei State.

  Wei Gongzi Ao led the vanguard of 200,000 Wei troops from Anyi and Luoyang, and encountered Wei Yang's forward troops at Huayin. Wei Yang thought that his well-trained army was invincible, so he sounded the drums and charged into battle with 50,000 Qin soldiers. However, a great general emerged from the Wei camp, riding a horse and wielding a sword, and charged straight at the Qin army.

  This general was none other than Wei Jia, a famous general of Wei State, who was already over 40 years old and had a long white beard. He wielded his sword with great skill, cutting down several Qin generals and charging into the enemy lines as if they were empty. The Wei soldiers saw this and their morale soared, fighting back against the Qin army.

  Wei Jia spotted Wei Yang and pointed his sword at him, shouting: "You shameless Wei Yang! You sold out your lord and sought glory for yourself, without any loyalty or filial piety. I will take your life, you three-surnamed traitor!" With that, he charged at Wei Yang on horseback, causing Wei Yang to turn around and flee in fear.

  The Qin generals rushed over to protect their commander, but Wei Jia shouted: "Anyone who blocks my way will die!" He swept his sword across the battlefield, cutting down several Qin generals. Wei Yang took advantage of the chaos to escape into the safety of his own lines.

  Just then, drums sounded from both the east and west directions, signaling the arrival of reinforcements from both sides. Wei Yang retreated 30 li in defeat.

  The next day, both armies formed up again, and Wei Yang rode forward to bow and say: "Wei Gongzi Ao, I have come to pay my respects." Wei Gongzi Ao replied: "You and I are like brothers, how could I not treat you with kindness?" Wei Yang said: "I am grateful for your kindness, but why did you betray me and attack Wei State?"

  Wei Yang explained that he had been forced to do so by the Qin king, and produced a letter as proof. The letter read: "The Qin king is cruel and has threatened my family, forcing me to lead an army against Wei State. I am deeply grateful for your kindness in the past, but I fear that I will not be able to repay you even if I were to die trying. Tonight, at the third watch, I will secretly cooperate with you to defeat the Qin army."

  Wei Gongzi Ao was moved by the letter and decided to trust Wei Yang. However, his general Wei Jia warned him: "Wei Yang is a treacherous man who would sell out his own family for personal gain. How can we trust him?" But Wei Gongzi Ao replied: "I treated him like a brother in the past, how could I suspect him of treachery now?"

  As a result, Wei Gongzi Ao led his army to attack the Qin camp at the third watch, but they fell into an ambush and were defeated. Wei Gongzi Ao was captured, and Wei Jia retreated back to Tongguan.

  Wei Yang then used Wei Gongzi Ao as a bargaining chip to demand that the king of Wei State cede the land west of the Yellow River to Qin. The king reluctantly agreed, and Wei Yang's reputation was forever tarnished by his treachery.