After the Qin army's major defeat of the Zhao forces at Changping in 261 BC, they besieged the Zhao capital of Handan, placing Zhao in imminent danger. The King of Zhao, greatly alarmed, urgently summoned Lord Pingyuan to the palace to discuss ways to make the Qin army withdraw. Lord Pingyuan said, "Given the current situation, we must seek help from other states. I am related by marriage to Lord Xinling, the younger brother of the King of Wei, and we have always had a good relationship. We can ask him to send troops to assist. The state of Chu is powerful, but it is too far from us. It would be better to propose that several states join forces to resist the strong Qin together. I am willing to go personally to handle this matter." The King of Zhao agreed.
Lord Pingyuan was a renowned nobleman of the Warring States period who treated talented and virtuous individuals with courtesy, befriending them regardless of their status, which attracted many followers. Among his numerous retainers, Mao Sui was ranked at the very bottom. Upon returning to his residence, Lord Pingyuan immediately gathered his retainers and informed them of his upcoming mission to the state of Chu to form an alliance against the state of Qin. He stated that he hoped to select twenty men to accompany him on this journey. Lord Pingyuan said, "This mission to Chu requires us to negotiate a joint resistance and establish a covenant, which will determine whether Handan can be defended and whether the state of Zhao will survive or perish. The stakes are extremely high, so we must succeed and cannot afford failure. If peaceful negotiations fail, we will have to resort to force. Therefore, the twenty selected must be proficient in both civil and martial arts. Since you are all talented and virtuous individuals, and the matter is urgent, these twenty will be chosen from among you."
Although Lord Pingyuan had many retainers, those skilled in civil affairs were not necessarily skilled in military matters, and those skilled in military matters were not necessarily skilled in civil affairs. After much selection, only nineteen suitable candidates were chosen, and the last suitable person could not be found no matter how hard they searched. Lord Pingyuan could not help but say, "I have been selecting talented and capable people for decades, gathering so many retainers, yet I never expected that I could not even select twenty people."
At this moment, Mao Sui, who was sitting in the very back row, stood up and said, "Although I have little talent, I am willing to accompany you." Lord Pingyuan looked at this man, realizing he had rarely seen him before and had never heard his attendants mention him, so he deliberately tested him, asking, "How long have you been under my patronage?" Mao Sui replied, "Three years." A hint of disdain immediately appeared in Lord Pingyuan's eyes as he said, "A truly talented and virtuous person in this world is like an awl placed in a pocket—it quickly pierces through and draws attention. Now, you have been here for three years, yet I have never heard anyone speak of you. This shows that you are not outstanding in either civil or military matters. Moreover, this mission to the State of Chu concerns the survival of our nation. With such a weighty responsibility, I fear your abilities are insufficient to bear it. You should stay here."
Lord Pingyuan said this, but Mao Sui did not back down at all. He immediately replied, "You make a fair point. A person of talent and virtue in this world can demonstrate their abilities, but to do so, they first need an opportunity. You are praised for knowing people well and treating them with courtesy, yet if you did not have the title of a prince of Zhao, how many would know of your discernment, and how would you have attained your current position? The reason I have not been noticed is simply that I never had the chance to be placed in a bag; otherwise, I would have emerged long ago, and not just poked a hole through it." Mao Sui's fluent and clear reasoning greatly astonished Lord Pingyuan. With time running short, Lord Pingyuan could not find another candidate elsewhere, so he agreed to let Mao Sui accompany him.
Although the other nineteen companions also heard what Mao Sui said, none of them took him seriously. They thought he was nothing more than a smooth talker, so they exchanged knowing smiles, mocking his overestimation of his own abilities. These nineteen men considered themselves highly learned, and along the journey, they chatted endlessly, discussing everything from east to west and criticizing current affairs. Mao Sui, however, remained silent most of the time, but whenever he did speak, his words were always incisive and his insights profound. By the time their group arrived in the State of Chu, the other nineteen had already become completely convinced of his abilities.
The military situation was urgent, so the very next morning after arriving in the State of Chu, Lord Pingyuan hurried to the Chu court to discuss forming a united front of six states against Qin with the King of Chu. The King of Chu said, "The alliance of the six states was originally initiated by Zhao, but it has never been able to hold firm. First, we made King Huai the leader of the alliance and jointly attacked Qin, but we failed to conquer it. Later, we made the King of Qi the leader, but each state pursued its own interests, and the alliance fell apart again. By now, talk of a six-state alliance has become taboo—even if we form one, each state has its own agenda and cannot unite, making it useless. Moreover, given Qin's current strength, which state can stand against it? It's better for each to seek its own safety and self-preservation. Besides, Chu has just established friendly relations with Qin, agreeing to mutual goodwill from now on. If Chu allies with Zhao again, wouldn't that violate our covenant with Qin? Such an action would surely invite war and disaster, essentially making Chu take the blame for Zhao. Let's not bring up the alliance anymore!" Fearing powerful Qin, the King of Chu dared not agree. Lord Pingyuan pleaded repeatedly, laying out the pros and cons, but even by noon, he had failed to persuade the king.
Mao Sui and the other nineteen retainers waited outside, growing impatient as Lord Pingyuan failed to emerge, so the nineteen said to Mao Sui, "Sir, go and see." Without a word, Mao Sui directly drew his sword, ascended the steps, and strode boldly into the hall, asking Lord Pingyuan, "The matter of the Six States' alliance only requires clarifying the pros and cons—just a few words. How can it be that after a whole morning, no conclusion has been reached?" The King of Chu, seeing someone dare to barge into the hall with a sword and speak so rudely, was furious. Yet, not knowing Mao Sui's background and intimidated by his imposing manner, he dared not scold him rashly. Instead, he first asked Lord Pingyuan, "Who is this person?" Lord Pingyuan replied, "This is my retainer, Mao Sui." The King of Chu immediately shouted in reprimand, "How insolent! I am discussing matters of state with your master—how dare you interrupt? Get out at once!"
Mao Sui, showing no fear, stepped forward with his sword and spoke passionately: "The alliance of the six states concerns the entire realm, so anyone in the world has the right to speak. How dare you rebuke me in front of my master—are you trying to humiliate someone? You rely solely on Chu's vast numbers and strength, but now I stand within ten paces of you, and no matter how many Chu soldiers there are, they cannot help you. I could take your life at any moment—what are you so arrogant about? Moreover, Shang Tang ruled over only seventy li of land and still became hegemon over the realm; King Wen of Zhou governed only a hundred li and still won the world's trust. Neither of them relied on numbers or bullied others through force. Chu, a great state with five thousand li of territory and a million soldiers, has every condition to dominate, yet it has been repeatedly crushed by Qin, suffering defeat after defeat, and even its own king was taken captive. Does Your Majesty not feel ashamed? The alliance of the six states against Qin is not just for Zhao's sake, but for Chu's as well. Yet you hesitate and waver—doesn't that feel utterly pathetic?" These words struck the King of Chu's sore spot.
The King of Chu, unable to find words to reply, nodded repeatedly. Mao Sui then asked, "So, do you agree to the alliance?" The King of Chu quickly answered, "Yes, I agree." Mao Sui immediately ordered the king's attendants, "Bring the blood!" The attendants brought a bronze basin filled with blood. Mao Sui lifted the basin, presented it with both hands to the King of Chu, and said, "Then let us seal the covenant with blood. Your Majesty first, then my master, and I will follow." After speaking, he called out to the nineteen men waiting outside the hall, "Gentlemen, you may drink below the steps! Are you not all useless people who can only accomplish things by relying on others?"
After returning to the state of Zhao, Lord Pingyuan remarked with deep emotion: "I prided myself on having a keen eye for talent, believing I would never overlook a single capable person. Yet I failed to recognize Mr. Mao's abilities even after he had served me for three years. In the court of Chu, Mr. Mao not only secured the alliance of the six states but also restored Zhao's dignity. Your silver tongue has proven mightier than a million soldiers. From now on, I dare no longer claim to be a talent scout." From that day forward, Mao Sui became Lord Pingyuan's most honored retainer.