Brief: This article explores the intense rivalry between the Vertical Alliance (Hezong) of Su Qin and the Horizontal Alliance (Lianheng) of Zhang Yi during the Warring States period. It details how Su Qin’s coalition of six states threatened Qin, only to be countered by Zhang Yi’s diplomatic stratagems that divided them. The narrative follows Su Qin’s dramatic mission to Qi, where he served as a double agent for Yan, secretly sabotaging Qi’s economy to maintain balance. The story culminates in Su Qin’s assassination, his posthumous trap to catch his killer, and the eventual collapse of his alliance, setting the stage for Zhang Yi’s greatest deception against the Chu-Qi coalition.
The execution of Shang Yang
In 338 BCE, Duke Xiao of Qin fell gravely ill and died. His son ascended the throne as King Huiwen of Qin.
Years earlier, as crown prince, King Huiwen had opposed Shang Yang’s reforms. In response, Shang Yang punished his two tutors: Gongsun Jia was branded on the face, and Gongzi Qian had his nose cut off – a humiliating punishment under Qin law.
Now king, Huiwen sought revenge. Encouraged by his disgraced former tutors, he accused Shang Yang of treason and had him executed – torn apart by chariots, according to some accounts.
Yet, despite killing the man, Qin kept every one of Shang Yang’s laws. The reforms had already transformed Qin into the most disciplined, wealthy, and militarily formidable state in the Warring States world. Its rise alarmed the six eastern powers – Han, Zhao, Wei, Qi, Chu, and Yan.
Fear bred unity.
The Huan River Covenant: A Challenge to Qin
In 333 BCE, Su Qin – now a celebrated diplomat – and Marquis Su of Zhao convened the rulers of Qi, Chu, Wei, Han, and Yan at the Huan River. There, they swore a solemn oath:
“If Qin attacks any one of us, all five shall come to its aid.”
This Vertical Alliance (Hezong) was more than diplomacy – it was a direct challenge to Qin’s ambition.
When King Huiwen of Qin heard the news, he summoned his chancellor, Gongsun Yan, in alarm:
“If the six states unite as one, how can Qin ever expand?”
Gongsun Yan urged immediate war:
“Attack Zhao first. If others rush to help, crush them one by one. Fear will break their alliance.”
But another voice rose in opposition.
Zhang Yi: Divide, Don’t Conquer
Zhang Yi, a brilliant strategist and former student of Guiguzi like Su Qin, sharply disagreed:
“They’ve just sworn brotherhood. Attack now, and you’ll only bind them tighter. Instead, befriend the nearest and the farthest – Wei and Yan. Give Wei back a few cities; offer your daughter in marriage to Yan’s crown prince. Once trust frays within the coalition, it will collapse from within.”
King Huiwen saw the wisdom in this. He abandoned war and launched a campaign of diplomatic seduction.
Soon, Wei – grateful for returned territory – and Yan – honored by a royal Qin bride – began drifting from the alliance.
The Fracture Begins
Marquis Su of Zhao was furious. He confronted Su Qin, the appointed “Leader of the Vertical Alliance”:
“You promised unity! Less than a year later, Wei and Yan are cozying up to Qin. Can we still count on the covenant?”
Cornered, Su Qin volunteered to fix the breach:
“Let me go to Yan, then Wei. I’ll bring them back.”
But fate had other plans.
A new crisis: Ten cities lost
When Su Qin arrived in Yan, Duke Wen had died. His successor, King Yi of Yan, immediately appointed Su Qin as chancellor – not out of trust, but as a test.
Just days earlier, Qi had invaded during Yan’s mourning period, seizing ten cities. King Yi challenged Su Qin:
“Your great alliance couldn’t stop Qi from stealing our land. As ‘Leader of the Alliance,’ what will you do?”
Su Qin, originally sent to scold Yan, now had to defend it. He traveled to Qi to confront King Wei of Qi.
There, he played a masterful hand:
“You’ve taken ten cities – but lost the trust of Yan and Qin (whose princess is now Yan’s queen). Return the cities, and both will hail you as a magnanimous leader. With their support, you – not Zhao – can lead the world.”
Flattered and ambitious, King Wei agreed. The ten cities were returned.
The Double Agent
Though hailed as a hero in Yan, Su Qin sensed growing jealousy from King Yi. Knowing his position was precarious, he proposed a bold ruse:
“Let me pretend to fall out with you and flee to Qi state. There, I’ll serve openly – but work secretly for Yan.”
King Yi consented. Su Qin “defected” to Qi.
King Wei welcomed him as a Guest Minister. But soon after, King Wei died, and his son King Xuan of Qi took the throne.
Undermining Qi from Within
King Xuan was capable – but flawed: he loved women and wealth. Su Qin exploited both.
He encouraged the king to:
- Build lavish palaces and gardens,
- Impose heavy taxes,
- Commission an extravagant tomb for his father.
All this drained Qi’s treasury and manpower.
Why? Because Su Qin believed true anti-Qin unity required balance among the six states. Qi was too strong – it threatened the coalition as much as Qin did.
His sabotage worked – until it didn’t.
Assassination and Posthumous Revenge
Qi’s ministers, especially Tian Wen (later known as Lord Mengchang, son of the late chancellor Tian Ying), saw through Su Qin’s scheme.
After Tian Wen gained influence, Su Qin’s enemies struck: assassins stabbed him.
Mortally wounded, Su Qin crawled to King Xuan and whispered a final stratagem:
“Cut off my head and hang it in the market. Declare: ‘Su Qin was a spy for Yan. His killer will be richly rewarded.’ The assassin will reveal himself.”
The king obeyed. Sure enough, a man boasted of the deed – and was arrested.
The Unraveling Truth
After Su Qin’s death, his servants gradually revealed the truth:
He had never betrayed Yan. His entire mission in Qi was to weaken it from within.
Enraged, King Xuan of Qi turned against Yan. In 314 BCE, when Yan descended into civil war, Qi invaded, killed its king, and nearly annexed the state.
Now Qi stood as the dominant eastern power – and soon forged an alliance with Chu, the southern giant.
For the first time, two superpowers – Qi and Chu – stood united against Qin.
The Stage for Zhang Yi’s Greatest Gambit
With the Qi-Chu alliance threatening to block Qin’s path to unification, Zhang Yi knew what must be done.
He approached King Huiwen of Qin:
“To achieve Lianheng (Horizontal Alliance), we must shatter Qi and Chu’s bond.”
And so, Zhang Yi set out for Chu – where his most famous deception awaited.
Note
Su Qin
Chief architect of the Vertical Alliance (Hezong) – a coalition of six eastern states against Qin. He later acted as a double agent to weaken Qi and maintain regional balance.
Zhang Yi
Master diplomat of Qin, creator of the Horizontal Alliance (Lianheng). He used division and deception to break up anti‑Qin coalitions.
King Huiwen of Qin
Ruler of Qin who adopted Zhang Yi’s strategy and laid the foundation for Qin’s future unification.
King Xuan of Qi
Qi’s ruler who was manipulated by Su Qin’s hidden sabotage.
Tian Wen (Lord Mengchang)
Influential noble of Qi who saw through Su Qin’s plot and supported his assassination.
Marquis Su of Zhao
Key supporter of the Vertical Alliance and host of the Huan River Summit.
Vertical Alliance (Hezong)
A north‑south coalition of six states (Qi, Chu, Yan, Han, Wei, Zhao) united to resist Qin’s expansion.
Horizontal Alliance (Lianheng)
Qin’s divide‑and‑rule strategy: forming bilateral alliances with individual states to isolate and destroy them one by one.
Huan River Covenant (333BCE)
The solemn oath that formally established the Vertical Alliance.
Double‑Agent Diplomacy
Su Qin’s secret mission: serving Qi openly while undermining it for Yan.
Posthumous Trap
Su Qin’s final stratagem to expose and punish his assassin after death.
Alliance vs. Division
The defining rivalry of the era: unity vs. manipulation.
Divide and conquer
Zhang Yi’s timeless tactic that destroyed Su Qin’s coalition.
Posthumous revenge
Su Qin’s legendary trick to catch his killer even after death.
Balance of power
Su Qin’s hidden goal: keeping all six eastern states equally strong to avoid internal domination.
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