During the late Warring States period, the seven major kingdoms were locked in endless conflict, with Qin growing the most powerful after Shang Yang's reforms boosted its economy and military, allowing it to frequently defeat the other six.
During the Warring States period, the strategist Su Qin championed the policy of "Vertical Alliance," uniting six states against the powerful Qin. To earn their trust, he devoured books and tirelessly refined his arguments, hoping to persuade each king.
That day, he drove his chariot to the State of Zhao to lobby. The King of Zhao received him with courtesy, personally descending the steps to greet him, and asked, "Honored guest, what advice do you have for me?"
Su Qin proposed the alliance of six states against Qin, but the King of Zhao was hesitant. Su Qin analyzed,
"The six states, when fighting Qin individually, are certainly no match for Qin in terms of weaponry, equipment, and soldier morale. Moreover, after Shang Yang's reforms, Qin's economy grew wealthier—a prosperous people makes a strong state. But how could Qin's ambition be satisfied with such a small territory?"
Su Qin continued, "The state of Zhao is vast and fertile—a fat sheep in the eyes of Qin. They would love nothing more than to attack and claim it for themselves. The only reason they haven't is that Han and Wei block their path to the southwest, giving Zhao a temporary peace. But once Qin swallows Han and Wei, won't Zhao find itself right in the jaws of the tiger?"
Hearing Su Qin's analysis, the King of Zhao trembled with fear, terrified that Zhao's kingdom might be destroyed by his own hand. At a loss, he leaned closer and asked, "Then, in your opinion, how can I preserve Zhao?"
“A single state indeed cannot withstand a mighty army. In my view, since Han, Wei, Qi, Chu, Yan, and Zhao are all threatened by Qin, it would be better to unite the forces of the six states and resist Qin together,” Su Qin replied.
Pointing to the map the King of Zhao had ordered brought in, Su Qin declared, "This map makes it perfectly clear: the combined territory of the six states is five times that of Qin, and their combined armies are ten times larger. If the six states fight Qin separately, each is weak and isolated, and ultimately no match for Qin. Eventually, they will be conquered one by one. But if the six states now form a vertical alliance, how could they possibly fear defeat by Qin?"
Su Qin continued, "And now those advocates of horizontal alliances are still persuading rulers to cede land to Qin in exchange for peace, or to bow down and declare themselves vassals. If this continues, the six states will weaken day by day, and the moment Qin makes a move, no one will be able to resist—they will simply surrender. My proposal of uniting the six states to defeat Qin is the complete opposite: one approach defeats and subdues the enemy, the other is to be defeated and subdued. These two outcomes are as different as heaven and earth—how could they even be mentioned in the same breath?"
Su Qin finally persuaded the King of Zhao, who appointed him prime minister, bestowed a hundred chariots, vast amounts of gold and jewels, and ordered him to unite the other five feudal lords.
Su Qin, with his exceptional eloquence, persuaded the rulers of six states. In 333 BC, the six states gathered at the Huan River, pledging to resist Qin together and forming an alliance. Su Qin was appointed "Chief of the Vertical Alliance," bearing the seals of all six states, and became a prominent figure of his time.
Later, people used the idiom "not to be mentioned in the same breath" to describe two vastly different things that cannot be compared.
Source: *Strategies of the Warring States*, Chapter "Strategies of Zhao II"
Meaning of the Idiom: Later, the Chinese idiom "不可同日而语" came to describe how two vastly different things cannot be compared.